WO1999022372A1 - A method and a system for transferring information using an encryption mode indicator - Google Patents

A method and a system for transferring information using an encryption mode indicator Download PDF

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Publication number
WO1999022372A1
WO1999022372A1 PCT/US1998/022126 US9822126W WO9922372A1 WO 1999022372 A1 WO1999022372 A1 WO 1999022372A1 US 9822126 W US9822126 W US 9822126W WO 9922372 A1 WO9922372 A1 WO 9922372A1
Authority
WO
WIPO (PCT)
Prior art keywords
mode
emi
information packet
information
sink device
Prior art date
Application number
PCT/US1998/022126
Other languages
French (fr)
Inventor
Teruyoshi Komuro
Yoshitomo Osawa
Hisato Shima
Tomoyuki Asano
Original Assignee
Sony Electronics, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sony Electronics, Inc. filed Critical Sony Electronics, Inc.
Priority to CA002308141A priority Critical patent/CA2308141C/en
Priority to DE69803394T priority patent/DE69803394T2/en
Priority to AU11035/99A priority patent/AU1103599A/en
Priority to EP98953748A priority patent/EP1012840B1/en
Priority to JP2000518385A priority patent/JP4185248B2/en
Priority to AT98953748T priority patent/ATE211575T1/en
Priority to KR10-2000-7004285A priority patent/KR100533225B1/en
Publication of WO1999022372A1 publication Critical patent/WO1999022372A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/40052—High-speed IEEE 1394 serial bus
    • H04L12/40058—Isochronous transmission
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/00731—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a digital rights management system for enforcing a usage restriction
    • G11B20/00746—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a digital rights management system for enforcing a usage restriction wherein the usage restriction can be expressed as a specific number
    • G11B20/00753—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a digital rights management system for enforcing a usage restriction wherein the usage restriction can be expressed as a specific number wherein the usage restriction limits the number of copies that can be made, e.g. CGMS, SCMS, or CCI flags
    • G11B20/00768—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a digital rights management system for enforcing a usage restriction wherein the usage restriction can be expressed as a specific number wherein the usage restriction limits the number of copies that can be made, e.g. CGMS, SCMS, or CCI flags wherein copy control information is used, e.g. for indicating whether a content may be copied freely, no more, once, or never, by setting CGMS, SCMS, or CCI flags
    • G11B20/00775—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a digital rights management system for enforcing a usage restriction wherein the usage restriction can be expressed as a specific number wherein the usage restriction limits the number of copies that can be made, e.g. CGMS, SCMS, or CCI flags wherein copy control information is used, e.g. for indicating whether a content may be copied freely, no more, once, or never, by setting CGMS, SCMS, or CCI flags wherein said copy control information is encoded in an encryption mode indicator [EMI]
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/0021—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving encryption or decryption of contents recorded on or reproduced from a record carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/40052—High-speed IEEE 1394 serial bus
    • H04L12/40104—Security; Encryption; Content protection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/40052—High-speed IEEE 1394 serial bus
    • H04L12/40117—Interconnection of audio or video/imaging devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs
    • H04N21/2347—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs involving video stream encryption
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
    • H04N21/4363—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network
    • H04N21/43632—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network involving a wired protocol, e.g. IEEE 1394
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
    • H04N21/4367—Establishing a secure communication between the client and a peripheral device or smart card
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/44—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream, rendering scenes according to MPEG-4 scene graphs
    • H04N21/4405—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream, rendering scenes according to MPEG-4 scene graphs involving video stream decryption
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H04N21/835—Generation of protective data, e.g. certificates
    • H04N21/8355—Generation of protective data, e.g. certificates involving usage data, e.g. number of copies or viewings allowed
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/913—Television signal processing therefor for scrambling ; for copy protection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
    • H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/913—Television signal processing therefor for scrambling ; for copy protection
    • H04N2005/91307—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal
    • H04N2005/91328—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal the copy protection signal being a copy management signal, e.g. a copy generation management signal [CGMS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/913—Television signal processing therefor for scrambling ; for copy protection
    • H04N2005/91357—Television signal processing therefor for scrambling ; for copy protection by modifying the video signal
    • H04N2005/91364—Television signal processing therefor for scrambling ; for copy protection by modifying the video signal the video signal being scrambled

Definitions

  • the present invention discloses a method and a svstem In one embodiment there is disclosed a method and svstem for transferring information using an encryption mode indicator
  • the present invention relates to the field of information communication systems More particularly, the present invention relates to the field of secure communication modes for information representing audio/visual works
  • AV information e g , representing AV works such as movies songs, etc
  • an information source e g , a video disk player or video cassette recorder
  • an information display device e g , a television set or monitor
  • an information sink device e g , a television set or monitor
  • the AV digital information that is transmitted (e g , representing movies) is usually protected by a copy ⁇ ght to prevent unauthorized users from viewing the information and making unauthorized reproductions of the AV works
  • the AV information is transmitted with encoded copy control information called the Copy Control Information (CCI) bits
  • CCI bits can also be referred to as Copy Generation Management System (CGMS) bits
  • CGMS Copy Generation Management System
  • the encoded CCI code is made up of 2 bits, of which "00,” “ 10,” and “1 1 " indicate "unlimited allowance for copies,” “allowance for a single generation copy, " and “inhibition of copy,” respectively
  • the "01 " bit code is left unused
  • the manner in which the CCI bits are added to an AV information is specified for the different kinds of AV information (e g , Motion Picture Expert Group MPEG, Digital Video DV and audio data)
  • These CCI bits are added within the data portion of data packets that constitute the AV information to control the use of the AV information by down stream devices
  • a recording device inspects the CCI code added to the AV information of a packet and refrains from recording them if the CCI code indicates the copy prohibition If the CCI code indicates the allowance of a single copy, the CCI code is changed to copy prohibition mode and then the AV information is recorded in a recording media once Thus, the copy generations allowed from the original data are limited
  • FIG. 1 illustrates fields of a prior art information packet 10 including a header section 12 in accordance with the IEEE 1394 standard, a packet (OP) header section 14 and a data field portion 16
  • the data packet is an isochronous packet
  • a special bit stream copy control information (BCI) field 20 is included within the CIP header section 14
  • the BCI field 20 contains the copy protection information for use when AV information is transmitted to a BSR device
  • the data section 16 can contain encrypted data
  • the CIP header section 14 is typically transmitted without encryption to accommodate the BSR's limited capabilities
  • the BSR device inspects the BCI field 20 of the packet header 14 and does not record the data if the packet indicates the copy inhibition but can record the data
  • FIG. 2 illustrates a system 30 in which the above copy protection can be compromised by an unauthorized device 34
  • a source device 32 transmits information to a sink device 36, which is a BSR device
  • An intercept device 34 is placed between this communication path (38a and 38b)
  • the BCI code 20 in the packet header 14 can be corrupted bv intercept device 34 while the packet is being transmitted from the transmitting device 32 to the receiving device 36
  • the transmitting device 32 transmits the BCI code 20 having the bit code " 1 1 " indicating the copy prohibition, but it is corrupted (by device 34) during the transmission into the bit code "10" indicating the single generation copy allowance or can be altered to the bit code "00" indicating no copy restriction at all
  • the BSR 36 is not informed of the fact that the data intrinsically should inhibit the copy and records the packet information because the BCI code of the packet header allows a single generation copy or unlimited copies Therefore, the copy generations cannot be controlled
  • a method and system are described for transferring information using an encryption mode indicator (EMI)
  • EMI encryption mode indicator
  • the present invention is useful in applications where copy protected information is to be transferred between devices, e g , in the transmission of audio/visual works that are subject to copyrights
  • the present invention can be used within the IEEE 1394 serial communication standard in which transmissions comprise individual packets of information
  • the present invention provides several secure information communication modes in which data (e g , representing an audio/visual work) can be transmitted from a source device to a sink device (receiving station) in a number of secure modes
  • data e g , representing an audio/visual work
  • EMI mode A the information of the transmission is not allowed to be copied as a whole work, this is the highest level of copy protection
  • EMI mode B the information of the transmission is allowed to be copied once and once only by the sink device
  • a third transmission mode no encryption is used and free copying is available
  • a different encryption process is used by the source device to encrypt the transmission
  • a different decryption process is used by the sink device to decrypt the transmission
  • the EMI code therefore indicates both (1) the copy protection mode of the transmission, and also (2) the encryption process used
  • the present invention is particularly useful for transmissions between a source device and a bit stream recorder which does not have the capability to extract copy control information from a packet header
  • one encryption process is used but two different cipher keys (key A and key B) are used to decrypt the data
  • the information is encrypted using a cipher key that is dependent upon the EMI code that is stored in the packet header If the EMI code is corrupted from mode A to mode B the sink device will decrypt the transmission by using the key "B " Since the encryption, in this example, is made by means of the key "A,” what is obtained by the sink device is a meaningless number What is recovered at the sink is not the original AV information in the least and are meaningless, even if recorded by the sink device BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is an illustration of fields within an information packet according to a copy control information (CCI) interface of the prior art
  • CCI copy control information
  • Figure 2 illustrates a block diagram of a system of the prior art having a source device and a sink device and an unauthorized intermediate device coupled between
  • Figure 3 illustrates a block diagram of one system in accordance with the present invention having a source device and a sink device coupled to communicate an information packet
  • FIG. 4 is an illustration of fields within an information packet including a encryption mode indicator (EMI) in accordance with the present invention including
  • Figure 5 A is a circuit diagram of a source device and a coupled sink device in accordance with a first embodiment of the present invention
  • Figure 5B is a circuit diagram of a source device and a coupled sink device in accordance with a second embodiment of the present invention
  • Figure 6A is a circuit diagram of components of a bit stream recording device in accordance with an alternative implementation of the first embodiment of the present invention
  • Figure 6B is a circuit diagram of components of a bit stream recording device in accordance with an alternative implementation of the second embodiment of the present invention
  • Figure 7 is a flow chart illustrating steps performed by a source device and a sink device in accordance with the present invention
  • FIG. 8 illustrates different types of audio/visual devices supported by the present invention and the va ⁇ ous communication modes supported by input signals to these devices and output signals from these devices
  • FIG. 9 illustrates operational modes within the present invention
  • the AV packet information is encrypted at the time when the packets are transmitted from the source device, and the cipher mode or encryption process that is used is altered according to an encryption mode indicator (EMI) code
  • EMI encryption mode indicator
  • the EMI code of the present invention represents three conditions, a copy prohibition mode, a single generation copy allowance mode and an unrestricted mode
  • the term "single generation copy” indicates that the original work may allow many copies to be made from it, but a copy of the original (e g , the one sent to the sink device) can be copied itself only once
  • the EMI information indicating the selected cipher mode is stored in a packet header If the EMI information is corrupted on the receiving side, the sink (e g , receiving) device will be unable to acquire the correct AV information from the packets because the sink device will decrypt in a cipher mode different from the genuine cipher mode
  • the cipher mode includes an encryption process, a cipher key, and can include an initial value of a register
  • the individual communications can be classified to use different cipher modes so that the transmitting device and the sink device can recognize the other device
  • FIG. 3 illustrates an exemplary system 100 of the many system configurations that are supported within the present invention
  • System 100 includes an optional wireless transmitter 1 10 which is capable of communicating digital AV information representing a digital program via broadcast channel 115
  • transmitter 1 10 can be a satellite broadcast unit
  • transmission line 1 15 is not wireless, but a cable
  • transmitter 1 10 is a land-based transmitter of a cable or pay-TV company
  • System 100 also includes a digital broadcast receiver unit 120
  • This unit 120 can also be called a set top box (STB)
  • receiver unit 120 is called the source device 120
  • the source device 120 contains EMI circuitry 150 in accordance with the present invention to support a number of EMI communication modes which are desc ⁇ bed further below Circuit 150 utilizes a different encryption mechanism for each EMI encryption mode
  • the source unit 120 is an intelligent device and contains specialized circuitry for processing copy protection standards For instance, source unit 120 receives a digital program over channel 1 15 and this digital program can be encoded using copy control information (CCI information)
  • CCI information copy control information
  • System 100 of Figure 3 also includes a sink device 130 which in this example is a bit stream recorder (BSR) unit 130 and is coupled to the source unit 120 using a serial interface 125
  • BSR bit stream recorder
  • sink unit 130 could also be any receiver unit shown in Figure 8
  • the sink unit 130 is a relatively simple device and, to keep costs down, does not contain the full complement of specialized circuitry required to fully process copy protection standards
  • sink unit 130 does not have the ability to decode CCI coded AV information
  • EMI circuitry 160 has the ability to decrypt AV information packets encrypted according to EMI codes
  • Sink unit 130 is coupled to receive digital information from the source unit 120 over a se ⁇ al line 125 Digital information is passed over line 125 using the IEEE 1394 communication standard Moreover, this information is forwarded in digital data packets that contain header information in a header portion and AV information (e g , data) in a data portion
  • EMI circuits 150 and 160 of Figure 8 are implemented such that each contains two cipher circuits so that information transmitted over line 125 is encoded under at least two different encryption mechanisms, A and B
  • EMI circuit 160 also has two cipher circuits so that it can (if allowed) decrypt information received over line 125 in mode A or in mode B encryption Rather than using a BCI code, the present invention uses an EMI code placed within data packets of line 125
  • the EMI code in addition to indicating the copy protection mode, also advantageously determines the encryption mode used in the data portion of the packet Therefore, the EMI circuit 160 within the sink unit 130 uses the EMI mode to select the proper decryption mechanism to decrypt the transmission received from line 125 Should be EMI code of the present invention be tampered with between the sink device 120 and the source device 130 (e g , by an intermediate intercept device), then EMI circuit 160, of the present invention, will select the wrong decryption mode In this instance, the original transmission will not be obtained by the
  • AV information packets which are transmitted over digital interface 125 They is copy free information, copy once information and copy prohibited information
  • the streams have different security levels of copy protection in accordance with the present invention
  • the manner in which copy protection is provided to each packet is called its EMI mode.
  • the EMI mode also indicates the mode of encryption that is applied to the AV information associated with the EMI mode.
  • EMI mode A is used to indicate that the packet data is copy prohibited. Under this mode A, AV information can only be rendered on a playback device (e.g., TV or monitor), but the AV information is not allowed to be recorded.
  • EMI mode B is used to indicate that the AV information can be copied (e.g., recorded) only one time to allow a single generation copy. This mode B also called single generation copy allowance mode.
  • EMI mode O is used when the AV information has no copy protection and therefore there is no copy limit. Mode O is also called unrestricted mode. For simplicity of description, no encryption is made for the mode O in the present embodiment. In the case of AV information in the copy control state allowing n number of copies (n>l), an extension can be made by defining the modes corresponding to the individual n-copies.
  • the EMI modes can be represented using a number of well known encoding techniques and can be represented using a register having at least two bits. In one particular embodiment of the present invention, a two bit register is used. Table I below illustrates exemplary coding numbers for each EMI mode. It is appreciated that the coding numbers selected within Table I are exemplary only and that any set of three unique numbers can be used.
  • AV information received over digital interface 125 can include multiple programs. Each program can have its own copy security level.
  • a copy prohibition stream (code 1 1) is a stream which includes at least one copy prohibited program.
  • a copy once stream (code 10) is a stream that has no copy prohibited programs and includes at least one copy once program.
  • device 130 is able to record only AV information received in EMI mode B (or EMI mode O) and can only pass through (or reject) AV information received in EMI mode A
  • Figure 4 illustrates the fields that constitute a typical information packet 200 in accordance with the present invention that are sent from the source unit 120 to the sink unit 130 ( Figure 3)
  • Information packet 200 of Figure 4 contains an IEEE 1394 header section 230 because, in one embodiment, the data packets conform to the IEEE communication standard
  • This header section 230 contains a data ength field, a tag field, a channel field, a tcode field and an sy field Aside from the tag and tcode fields, header 230 conforms to the well known IEEE standard and the other fields are defined therein
  • the tag field indicates that the data field starts with a CIP header 240
  • the tcode field can be one of two predetermined values It is appreciated that a data stream means a stream of information on one 1394 isochronous channel Information packet 200 also contains a CIP header section 240
  • the CIP header section 240 contains an EMI field 210 that in one implementation is two bits wide and contains the EMI mode value as defined in Table I The EMI mode value corresponds to the
  • EMI modes within field 210 indicate the copy control status of the data stream on the 1394 isochronous stream
  • the data stream in accordance with the present invention can consist of several video and/or audio programs and each of them can have a different copy control information associated with the program
  • the MPEG transport stream output from a source unit can contain several programs, each of which can have a different level of copy protection
  • the source device assigns the EMI value for the most rest ⁇ ctive program in the stream
  • a bit stream recorder may or may not record the entire stream based on the EMI value
  • Another type of recording device which is capable of processing each program in the stream individually and is also capable of interpreting copy control information associated with each program is called a format cognizant recording device
  • a format cognizant recording device refers control information associated with each program to decide its action EMI CIRCUITRY OF THE PRESENT INVENTION
  • Figure 5 A illustrates a system 400 of the present invention having a source device 120 and a sink device 130
  • Figure 5A illustrates the EMI circuitry 150 of a typical source unit 120 in more detail
  • Source unit 120 can be a set-top-box (STB) unit also called a broadcast receiver which contains many well known circuits (not shown for clarity) in addition to the EMI circuit 150
  • a receiver circuit 410 receives AV information in the form of data packets and performs any decryption required under CCI standards The result is forwarded over communication interface 430 and also to a de-multiplexer (de-mux) 414 using interface 413
  • Circuit 412 is an EMI mode select circuit and depending on the recovered CCI copy protection information will select either EMI mode A or EMI mode B if copy protection is required If no copy protection is required, then interface 413 is passed directly to interface 125 and EMI mode O (code "00") is inserted into EMI field 210 of the data packet
  • select circuit 412 controls de-mux 414 via signals over line 426
  • EMI mode A is selected, then the data packet from 413 is routed to encrypt unit A 418 which encrypts the data portion (e g , field 220) of the data packet according to a cipher key 416 and according to a first encryption technique within encryption unit A 418 Unit 418 also places the "1 1" code (EMI mode A) within the EMI mode field 210 of the data packet
  • the result is then passed to multiplexer (mux) 422 which is also controlled by line 426 Mux 422 passes the output from encryption unit A 418 to interface 125 using the optional output driver 424
  • EMI mode B is selected, then the data packet from 413 is routed to encrypt unit B 420 which encrypts the data portion (e g , field 220) of the data packet according to the key 416 and according to a second encryption technique within encryption unit B 420 Unit 420 also places the "10" code (EMI mode B)
  • Sink device 130 of Figure 5A contains many well known circuits (not shown for clarity) in addition to EMI circuit 160 EMI circuit 160 within the sink device 130 of Figure 5 A contains a decryption unit A 448 which can decrypt an encryption made bv encryption unit A 418, assuming cipher key 452 coincides with key 416 and also contains a decryption unit B 450 which can decrypt an encryption made by encryption unit B 420, assuming key 452 is correct
  • the data packet of interface 125 is received by a de-multiplexer circuit 442 and also by an EMI mode extractor circuit 440 Circuit 440 extracts the header information from the received data packet and extracts the EMI field 210 from the header Depending on the EMI mode extracted circuit 440 controls signals over line 446 If EMI mode O is extracted, then the data packet over line 125 is directly coupled to the bit stream recording media 456 or is allowed to be directly output over line 470 without inhibition
  • circuit 440 extracts EMI mode A, then the data packet from interface 125 is routed through de-mux 442 to decryption unit A 448 which decrypts the data portion of the data packet (using key 452) and forwards the result to mux 454 which is also controlled bv select line 446 Mux 454 routes the data packet from the output of decryption unit A 448 to the output line 470 only When the sink device 130 is a BSR device, it is not allowed to record an EMI mode A data packet, so recording to the BSR media 456 is prohibited in this case If circuit 440 extracts EMI mode B, then the data packet from interface 125 is routed through de-mux 442 to decryption unit B 450 which decrypts the data portion of the data packet, changes the EMI mode to EMI mode A, records the "1 1 " code (mode A) in the EMI field 210, and forwards the result to mux 454 which is also controlled by select line 446 Mux 454 routes the data packet from the output of decrypt
  • FIG. 6A illustrates the block diagram 665 of an alternative embodiment of the EMI circuitry for a bit stream recording sink device 130 without the decrypt unit A
  • the EMI extractor 440 detects mode A in the input 125 it stops the decrypt unit B 450 and stops the BSR recording unit 456
  • Circuit 400 of Figure 5 A prevents intermediate devices from compromising the copy protection m the following manner If an EMI mode A data packet is altered on line 125 to an EMI mode B data packet the sink device 130 will use the wrong decryption unit when attempting to recover the data The result becomes meaningless information recorded by BSR media 456 If an EMI mode A or an EMI mode B data packet from interface 125 is altered to an EMI mode O data packet, then sink device 130 will not perform any decryption and the result is not renderable
  • Figure 5B illustrates a system 500 of the present invention having a source device 120' and a sink device 130'
  • Figure 5B illustrates the EMI circuitry 150' of a typical source unit 120' and EMI circuitry 160' of a typical sink unit 130'of an alternative embodiment of the present invention
  • a common encryption unit and a common decryption unit are used, but they receive different cipher keys (Key A, Key B) depending on the EMI mode selected, this provides the two encryption-decryption mechanisms
  • Source unit 120' of Figure 5B can be a set-top-box (STB) unit also called a broadcast receiver which contains many well known circuits (not shown for clarity) in addition to EMI circuit 150'
  • a receiver circuit 510 receives AV information in the form of a data packet and performs any decryption required under CCI standards The result is forwarded over communication interface 512 (coupled to an EMI mode selected circuit 514) and also to an interface 513
  • Circuit 514 is an EMI mode select circuit and depending on the recovered CCI copy protection information will select either EMI mode A or EMI mode B, if copy protection is required If no copy protection is required, then interface 513 is passed directly to interface 125 and EMI mode O (code "00") is inserted into EMI field 210 of the data packet
  • select circuit 514 controls the select line of multiplexer (mux) 516
  • Common key 524 is routed to hash circuit A 520 having a first hash function which generates a first cipher key (key A) at its output
  • Key 524 is also routed to hash circuit B 522 having a second, different, hash function which generates a second cipher key (key B) at its output
  • mux 516 selects key A to forward to common encryption unit 518 which encrypts the data portion (e g , field 220) of the data packet according to key A and according to a common encryption technique within encryption unit 518
  • Unit 518 also places the "11" code (EMI mode A) within the EMI mode field 210 of the data packet
  • EMI mode A the "11" code
  • mux 516 of Figure 5B selects key B to forward to common encryption unit 518 which encrypts the data portion (e g field 220) of the data packet according to key B and according to the common encryption technique within encryption unit 518 Unit 518 also places the "10" code (EMI mode B) within the EMI mode field 210 of the data packet The result is then passed over interface 530 to an optional driver circuit 526 which outputs the data packet to interface 125
  • two different keys (A and B) are used to alter the encryption process used in the single common encryption unit 518
  • the key 524 can be established during a source-sink authentication process After sharing a covert channel key, Kc, the source device 120' and the sink device 130' share work keys, A and B First, the source device 120' sends a random number Na to the sink device 130' The source device and the sink devices use internal EMI circuitry to compute the work keys (Key A and Key B) by
  • Hkc a keyed hash function using a key Kc and Ca and Cb are constant and are licensing codes
  • Circuit 150' is advantageous because it only requires a single encryption unit 518 Although two hash function circuits 520, 522 are required, this additional circuitry is generally less than the circuitry eliminated by eliminating the second encryption unit This is particularly true if the hash functions are implemented in software Hash functions are readily implemented in software because the function needs to be determined only once for a given key
  • Sink device 130' of Figure 5B contains many well known circuits (not shown for clarity) in addition to EMI circuit 160' EMI circuit 160' within the sink device 130' contains a single common decryption unit 544 which can decrypt an encryption made by common encryption unit 518, assuming the corrected common key is supplied
  • the data packet of interface 125 is received by an EMI mode extractor circuit 540 Circuit 540, like circuit 440, extracts the header information from the received data packet and extracts the EMI field 210 from the header Depending on the EMI mode extracted, circuit 540 controls the select line of mux 542 If EMI mode O is extracted by circuit 540, then the data packet over line 125 is directly coupled to the bit stream recording media 550 or is allowed to be directly output over line 570
  • EMI extraction circuit 540 controls the select line of multiplexer (mux) 542
  • Key 554 is routed to hash circuit A 546 having the first hash function which generates the first cipher key (kev A) at its output
  • Key 554 is also routed to hash circuit B 548 having the second, different, hash function which generates the second cipher key (key B) at its output.
  • mux 542 selects key A to forward to common decryption unit 544 which decrypts the data portion (e.g., field 220) of the data packet according to key A and according to a common decryption technique within decryption unit 544 Unit 544 also places the "1 1 " code (EMI mode A) within the EMI mode field 210 of the data packet. The result is routed to the output line 570 only.
  • the sink device 130' is a BSR device, it is not allowed to record an EMI mode A data packet, so recording to the BSR media 550 is prohibited in this case.
  • mux 542 of Figure 5B selects key B to forward to common decryption unit 544 which decrypts the data portion (e.g., field 220) of the data packet according to key B and according to the common decryption technique within decryption unit 544 Unit 544 also places the "1 1 " code (EMI mode A) within the EMI mode field 210 of the data packet.
  • EMI mode A is then passed over interface 552 to a BSR recording media 550 and optionally to an output interface 570
  • the sink device 130' is a BSR device, it is allowed to record an EMI mode B data packet only once, so this data packet is changed to an EMI mode A packet prior to recording to the BSR media 550.
  • two different keys (A and B) are used to alter the decryption process used in the single common decryption unit 544
  • the key 554 (same as 524) can be established during a source-sink authentication process.
  • Circuit 160' is advantageous because it only requires a single decryption unit 544 Although two hash function circuits 546, 548 are required, this additional circuitry is generally less than the circuitry eliminated by eliminating the second decryption unit. Hash functions 546, 548 are readily implemented in software because the function needs to be determined only once for a given key.
  • FIG. 6B illustrates the block diagram 670 of an alternative embodiment of the EMI circuitry for a bit stream recording sink device 130' without the hash A circuit.
  • the EMI extractor 540 detects mode A in the input 125, it stops the common decrypt unit 544 and stops the BSR recording unit 550
  • Circuit 500 of Figure 5A prevents intermediate devices from compromising the copy protection in the following manner. If an EMI mode A data packet is altered on line 125 to an EMI mode B data packet, the sink device 130' will use the wrong decryption key (between key A and key B) when attempting to recover the data The result is meaningless information recorded by BSR media 550 If an EMI mode A or an EMI mode B data packet from interface 125 is altered to an EMI mode O data packet, then sink device 130' will not perform any decryption and the result is not renderable
  • FIG. 7 illustrates a flow diagram 700 of steps performed by the present invention with respect to system 400 of Figure 5A
  • authentication is performed so that sink device and source device recognized each other
  • This process can be performed using various predetermined license and service keys
  • Any of a number of well known authentication and secure key exchange processes can be used at step 710 in accordance with the present invention
  • special codes are exchanged if authentication was successful and step 720 is entered If authentication failed, then at step 715, process 700 returns without any AV information exchanged
  • the source device 120 utilizes the special codes to send an encrypted key to the sink device 130 which decrypts the key
  • key 416 and key 452 are established between the source and sink devices and these keys are of the same value
  • the source device 120 receives a data packet having a first copy protection mode (e g , using CCI modes) and translates this CCI mode into an EMI mode (e g , copy prohibited, copy once, unrestricted)
  • the circuit 150 places the proper EMI mode into the header of the received data packet and encrypts the data portion of the data packet using one of two possible encryption mechanisms according to the EMI mode This data packet is then forwarded over interface 125
  • step 740 of Figure 7 the since device uses circuit 160 to extract the EMI mode and decrypt the data packet according to the EMI mode that was extracted One of two possible decryption mechanisms are used based on the EMI mode This information is recorded in EMI mode A (full protection) if EMI mode B was received If EMI mode A was received, then no recording is allowed At step 760, if more data packets are required, then process 700 returns to step 740 to process the next data packet Otherwise, process 700 returns
  • Figure 8 illustrates a number of different classes of devices that can be used in accordance with the present invention
  • the dotted signal lines represent AV information packets in EMI mode B and the solid signal lines represent AV information packets in EMI mode A
  • the first device class is device class A
  • These devices include transmitting devices that can add the EMI code to their packet information and also include those devices that can receive CCI data
  • An example is a set-box (STB) 120 which is able to receive a satellite broadcast (e g , in CCI format) and transmit the data over the IEEE 1394 bus
  • the STB device 120 can generate AV transmission packets encrypted under either EMI mode A or EMI mode B
  • the STD device 120 can also generate AV transmissions that are unrestricted Device 120 supplies AV information in EMI mode B as shown by output 626 and in EMI mode A as shown by output 628
  • the second device class is device class B These devices include receiving or sink devices that are capable of responding to the EMI information that is present within AV information packets
  • An example device within class B is the format cognizant recorder device 630
  • This device 630 is able to properly decrypt the received AV information packets in any EMI mode, record the AV information using the IEEE 1394 standard format, record the EMI information added thereto and transmit the reproduced data using the IEEE 1394 standard format If the AV information received is o ⁇ ginated in EMI mode B, when recorded it is altered to EMI mode A to prevent further copies
  • Device 630 is able to receive AV information packets encrypted in EMI mode B 632 and in EMI mode A 634 but only can supply AV information encrypted in EMI mode A 636
  • the third device class is device class C These devices include receiving devices that are incapable of fully processing certain copy protection information (e g under CCI modes) because these devices lack the specialized circuitry required to fully process this copy protection information
  • class C is the bit stream recorder (BSR) device 130 of Figure 8 It is capable of receiving only AV information encrypted in EMI mode B via input 610 and is capable of supplying only AV information encrypted in EMI mode A via output 615
  • the BSR device 130 is capable of decrypting mode B encryption using the extracted EMI code and storing this information, if EMI mode B is received
  • the BSR device 130 can also reproduce AV information and transmit this information in EMI mode A under the IEEE 1394 standard
  • the fourth device class is device class D.
  • These devices include receiving devices that can process EMI information which is added to the information packets.
  • An example of a class D device is digital television 620.
  • the digital TV set 620 is able to receive AV information encrypted in EMI mode B via input 622 and encrypted in EMI mode A via input 624, under the IEEE 1394 standard.
  • the digital TV 620 is able to decrypt AV information from either EMI mode A or EMI mode B and render the AV information.
  • Encryption and decryption modes can be licensed by an entity depending on the functions which the entity wants to achieve. If the entity manufactures display devices, licenses for decryption of EMI mode A and EMI mode B are necessary. If the entity manufactures a BSR unit 130, decryption of EMI mode B and encryption for EMI mode A are necessary. EMI modes A and B can be combined with license keys and service keys, as described below with respect to one embodiment of the present invention.
  • particular communication services are supported.
  • particular secrets e.g., key codes
  • Transmissions within service 1 include transmitting devices of Classes A, B, or C with receiving devices of Classes A, B, or C.
  • Transmissions within service 2 include transmitting devices of Classes A, B, or C with receiving devices of Class D.
  • Transmissions within service 3 include transmitting devices of Class D with receiving Devices of Classes A, B, or C.
  • a source unit which recognizes CCI copy protection format sends AV information to a sink unit which also recognizes this CCI format (e.g., STD --> display, or, STB --> format cognizant recorder). Both source and sink are copy protection intelligent devices.
  • a source unit which recognizes the CCI format sends AV information to a sink unit which does not recognize CCI format but is implemented to recognize the EMI codes in accordance with the present invention (e.g., STB --> BSR unit).
  • the sink unit does not have the same level of copy protection intelligence as the source unit.
  • a source unit that does not recognize CCI format sends AV information to a sink unit that recognizes CCI format (e g , DVHS --> Display)
  • secret codes e g , key codes
  • secret codes for using the EMI modes A and B and the services 1, 2, and 3 are given (e g , licensed) to the devices of the individual classes enumerated above
  • a key code or "secret” is used by the two devices for performing secure key transmissions du ⁇ ng authentication, as described above. In this manner, the keys that are described above and used for encryption and decryption can safely be transmitted between the source and sink devices
  • the device classifications can be further refined according to types of data such as MPEG or DV
  • a pair including a service key and a license key is allocated to services 1, 2, and 3, respectively
  • a source unit has a service key and a sink unit has the licensed key corresponding to its supported services Therefore, services 1, 2 and 3 are distinguished by service key or license key
  • STB unit 120 can give service 1, 2 so STB unit 120 has service key 1 and
  • the DVHS 130 can receive service 2 and give service 3 so D ⁇ ⁇ S 130 has license key 2 and service key 3
  • Each service can be divided into sub services within it own service group
  • a set of encryption mode(s), service mode(s) and license key(s) is given to a unit depending on the functions the device should have
  • a display device 620 could have decryption EMI mode A and EMI mode B and license keys for services 1 and 3
  • the STB unit 120 could have encryption for EMI mode A and EMI mode B and service keys for service 1 and service 2
  • the DV ⁇ S (BSR) unit 130 could have decryption for EMI mode B, encryption for EMI mode A and license key for service 2 and service key for service 3
  • the devices of Class A are required to have key codes for the transmitting devices of services 1 and 2 and key codes for EMI modes A and B and are provided key codes Secret IT, Secret IT, Secret 2T, Secret 2T, Secret A, and Secret B
  • the devices of Class B are required to have key codes for the receiving devices of service 1 and 3, a key code for the transmitting device of Service 1, and key codes for Modes A and B, and are provided key codes Secret 1R, Secret 1R, Secret 3R, Secret 3R, Secret A, and Secret B
  • the devices of Class C are required to have key codes for the receiving devices of Services 1 and 3 and key codes for Modes A and B and are provided key codes Secret 1R Secret 1R, Secret 3R, Secret 3R, Secret A, and Secret B
  • the devices of Class D are required to have a key code for the receiving device of Service 2 and a key code for the transmitting device of Service 3 and are provided key codes Secret 2R, Secret 3T, Secret A, and Secret B
  • Mode A only for the transmissions and the use of Mode A only
  • the following procedure describes the manner in which data packets are transmitted from a source device of class A to a sink device of class B acting as a receiving device
  • the data packets are transmitted from source device to sink device and are recorded by the sink device
  • the source device at the transmission side generates Kseed as a data key for encrypting the data packets
  • the source device safely delivers the data key Kseed to the sink device at the reception side using the secrets Secret IT and Secret 1R for the transmitting device and the receiving device of Service 1
  • the source device makes an encryption Key A for Mode A and a cipher Key B for Mode B by employing Kseed, Secret A, and Secret B Specifically, calculations are made by using
  • the source device reads the value of the CCI added to the data to be transmitted If the CCI indicates the copy inhibition, the data packet is encrypted together with the CCI by means of the cipher Key A for Mode A
  • the EMI mode (“1 1 ") is stored in field 210 and the data packet is transmitted over the IEEE 1394 interface If the CCI indicates the single generation copy allowance, the data are encrypted together with the CCI by means of the cipher key B for Mode B, and the EMI mode ("10") is stored and packeted in the EMI mode field 210 of the data packet and the packet is transmitted over the IEEE 1394 interface If the CCI indicates no copy limit, the data packet is not encrypted but packeted
  • the EMI mode is stored as "00,” in field 210 and the packet is transmitted Therefore, what key the transmitting device uses to encrypt the data does not depend upon the service but is determined by the EMI mode added to the data
  • the sink device Like the source device, the sink device generates Key A and Key B from Kseed Secret A, and Secret B
  • the EMI of the received packet is inspected by the sink device, and the data is decrypted by using the key A, if the EMI mode indicates Mode A, and by using key B if the EMI mode indicates Mode B
  • the EMI mode added to the decrypted data is inspected
  • the data are not recorded if the EMI mode indicates the copy inhibition
  • the EMI mode is changed, if it indicates the single generation copy allowance, into the copy inhibition and is recorded together with the data
  • the EMI mode is recorded together with the data, if it indicates no copy limit
  • the source device delivers the Kseed safely to the sink device
  • the secrets to be used here are Secret 2T and Secret 2R
  • the source device generates the keys Key A and Key B, as described above, and encrypts the data in dependence upon the EMI mode added to the data
  • the source device stores the proper EMI in the packet header and transmits it
  • the sink device generates the key B in a manner similar to that of source device Assume the sink device is inhibited to use Mode A for receptions by the license conditions so that it does not generate key A
  • the sink device inspects the EMI mode of the received packet The sink device discards the packet if the EMI mode indicates Mode A If the EMI mode indicates Mode B, the sink device decrypts the data by means of the kev B and records the packets At this time, the information indicating that the data have been encrypted in mode B is recorded together with the data If the EMI mode indicates 00, the sink device records the data as they are At this time, the information indicating that the data have not been encrypted is recorded together with the data

Abstract

A method and system for transferring information using an encryption mode indicator (EMI). The present invention provides several secure information communication modes in which data (e.g., representing an audio/visual work) can be transmitted from a source device to a sink device (receiving station) in a number of secure modes. In one secure mode, EMI mode A, the information of the transmission is not allowed to be copied as a whole work; this is the highest level of copy protection. In second secure mode, EMI mode B, the information of the transmission is allowed to be copied once and once only by the sink device. In a third transmission mode, no encryption is used and free copying is availabe. Depending on which secure mode is selected between mode A and mode B, a different encryption process is used by the source device to encrypt the transmission. Further, depending on which secure mode is selected between mode A and mode B, a different decryption process is used by the sink device to decrypt the transmission. The present invention is particularly useful for transmissions between a source device and a bit stream recorder which does not have the capability to extract certain encryption information from a packet header. By using different encryption processes for each transmission mode, an unauthorized device placed between the source and the sink devices that alters the EMI code will be unable to thereafter render or record the audio/visual work because the decryption process selected will differ from the encryption process used.

Description

A METHOD AND A SYSTEM FOR TRANSFERRING INFORMAΗON USING AN ENCRYPΗON MODE INDICATOR
BACKGROUND OF THE INλΕNTION
FIELD OF THE INλΕNTION
The present invention discloses a method and a svstem In one embodiment there is disclosed a method and svstem for transferring information using an encryption mode indicator The present invention relates to the field of information communication systems More particularly, the present invention relates to the field of secure communication modes for information representing audio/visual works
RELATED ART
In recent years there has been a technique, bv which a plura tv of audio/visual (AV) devices can be connected using digital interfaces so that AV information (e g , representing AV works such as movies songs, etc ) can be transmitted from an information source (e g , a video disk player or video cassette recorder) to an information display device (e g , a television set or monitor) or an information sink device The development of this technology as led to the adoption of the IEEE 1394 serial communication standard for AV devices Within the IEEE 1394 seπal communication standard, information is transmitted in digital packets having certain header information and having data sections
The AV digital information that is transmitted (e g , representing movies) is usually protected by a copyπght to prevent unauthorized users from viewing the information and making unauthorized reproductions of the AV works To prevent unauthorized copying, the AV information is transmitted with encoded copy control information called the Copy Control Information (CCI) bits The CCI bits can also be referred to as Copy Generation Management System (CGMS) bits The encoded CCI code is made up of 2 bits, of which "00," " 10," and "1 1 " indicate "unlimited allowance for copies," "allowance for a single generation copy, " and "inhibition of copy," respectively The "01 " bit code is left unused The manner in which the CCI bits are added to an AV information is specified for the different kinds of AV information (e g , Motion Picture Expert Group MPEG, Digital Video DV and audio data) These CCI bits are added within the data portion of data packets that constitute the AV information to control the use of the AV information by down stream devices
At each data recording time, a recording device inspects the CCI code added to the AV information of a packet and refrains from recording them if the CCI code indicates the copy prohibition If the CCI code indicates the allowance of a single copy, the CCI code is changed to copy prohibition mode and then the AV information is recorded in a recording media once Thus, the copy generations allowed from the original data are limited
Moreover, in order to enforce the copy generation limiting system, there has been employed a method by which CCI codes are encrypted into the data portions of the information and the decryption information is licensed to the manufacturer that has made a contract to manufacture only a device conforming to the copy generation limiting system In order for the recording device to inspect or alter the CCI code encrypted within the AV information, it is necessary to provide a microcomputer mounted on the device or to provide specialized hardware for the processing In order to match numerous kinds of AV information, the required decryption circuitry is relatively complex, increasing the cost of the device
For an inexpensive recording device, e g , a bit stream recording (BSR) device, it is conceivable to manufacture the device without the ability to read the CCI codes within the AV information because the above specialized hardware is eliminated For this inexpensive BSR device, it has been conceived to provide a unique field within the AV packets to store copy protection information Figure 1 illustrates fields of a prior art information packet 10 including a header section 12 in accordance with the IEEE 1394 standard, a packet (OP) header section 14 and a data field portion 16 The data packet is an isochronous packet A special bit stream copy control information (BCI) field 20 is included within the CIP header section 14 The BCI field 20 contains the copy protection information for use when AV information is transmitted to a BSR device Although the data section 16 can contain encrypted data, the CIP header section 14 is typically transmitted without encryption to accommodate the BSR's limited capabilities In response to this packet 10 the BSR device inspects the BCI field 20 of the packet header 14 and does not record the data if the packet indicates the copy inhibition but can record the data if the same indicates the single generation copy allowance or the unlimited allowance If allowed, the packet information can be recorded by the BSR device together with the BCI code 20 which is stored in the packet header 14 Provided the original packet header indicated the single generation copy allowance, when the recorded information is reproduced and supplied from the BSR device to the IEEE 1394 bus the recovered BCI code 20 will indicate copy inhibition (because it has already copied once) However, the same BCI code is stored and transmitted if the original BCI code indicated no copy limit
Figure 2 illustrates a system 30 in which the above copy protection can be compromised by an unauthorized device 34 As shown, a source device 32 transmits information to a sink device 36, which is a BSR device An intercept device 34 is placed between this communication path (38a and 38b) The BCI code 20 in the packet header 14 can be corrupted bv intercept device 34 while the packet is being transmitted from the transmitting device 32 to the receiving device 36 For instance, the transmitting device 32 transmits the BCI code 20 having the bit code " 1 1 " indicating the copy prohibition, but it is corrupted (by device 34) during the transmission into the bit code "10" indicating the single generation copy allowance or can be altered to the bit code "00" indicating no copy restriction at all In response to this packet, the BSR 36 is not informed of the fact that the data intrinsically should inhibit the copy and records the packet information because the BCI code of the packet header allows a single generation copy or unlimited copies Therefore, the copy generations cannot be controlled
Accordingly, what is needed is a copy protection system whereby packet information can be transmitted from a source device to an unintelligent device without compromise by an intermediate device What is further needed is a copy protection system whereby packet information can be transmitted from a source device to a BSR device without compromise by an intermediate device What is needed further is a system that does not allow copv protection mode information within a transmission to be altered and yield usable results at the sink device The present invention provides such advantageous features These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein
SUMMARY OF THE INVENTION A method and system are described for transferring information using an encryption mode indicator (EMI) The present invention is useful in applications where copy protected information is to be transferred between devices, e g , in the transmission of audio/visual works that are subject to copyrights The present invention can be used within the IEEE 1394 serial communication standard in which transmissions comprise individual packets of information
The present invention provides several secure information communication modes in which data (e g , representing an audio/visual work) can be transmitted from a source device to a sink device (receiving station) in a number of secure modes In one secure mode, EMI mode A, the information of the transmission is not allowed to be copied as a whole work, this is the highest level of copy protection In second secure mode, EMI mode B, the information of the transmission is allowed to be copied once and once only by the sink device In a third transmission mode, no encryption is used and free copying is available Depending on which secure mode is selected between mode A and mode B, a different encryption process is used by the source device to encrypt the transmission Further, depending on which secure mode is selected between mode A and mode B, a different decryption process is used by the sink device to decrypt the transmission The EMI code therefore indicates both (1) the copy protection mode of the transmission, and also (2) the encryption process used
The present invention is particularly useful for transmissions between a source device and a bit stream recorder which does not have the capability to extract copy control information from a packet header By using different encryption processes for each transmission mode an unauthorized device placed between the source and the sink devices that alters the EMI code will be unable to thereafter render or record the audio/visual work because the decryption process selected will differ from the encryption process used
In one embodiment of the present invention, one encryption process is used but two different cipher keys (key A and key B) are used to decrypt the data In this embodiment, the information is encrypted using a cipher key that is dependent upon the EMI code that is stored in the packet header If the EMI code is corrupted from mode A to mode B the sink device will decrypt the transmission by using the key "B " Since the encryption, in this example, is made by means of the key "A," what is obtained by the sink device is a meaningless number What is recovered at the sink is not the original AV information in the least and are meaningless, even if recorded by the sink device BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an illustration of fields within an information packet according to a copy control information (CCI) interface of the prior art
Figure 2 illustrates a block diagram of a system of the prior art having a source device and a sink device and an unauthorized intermediate device coupled between
Figure 3 illustrates a block diagram of one system in accordance with the present invention having a source device and a sink device coupled to communicate an information packet
Figure 4 is an illustration of fields within an information packet including a encryption mode indicator (EMI) in accordance with the present invention including
Figure 5 A is a circuit diagram of a source device and a coupled sink device in accordance with a first embodiment of the present invention
Figure 5B is a circuit diagram of a source device and a coupled sink device in accordance with a second embodiment of the present invention
Figure 6A is a circuit diagram of components of a bit stream recording device in accordance with an alternative implementation of the first embodiment of the present invention
Figure 6B is a circuit diagram of components of a bit stream recording device in accordance with an alternative implementation of the second embodiment of the present invention
Figure 7 is a flow chart illustrating steps performed by a source device and a sink device in accordance with the present invention
Figure 8 illustrates different types of audio/visual devices supported by the present invention and the vaπous communication modes supported by input signals to these devices and output signals from these devices
Figure 9 illustrates operational modes within the present invention
DETAILED DESCRIPTION OF THE INVENTION
In the following detailed description of the present invention, a method and system for providing secure transmission of copy protected information between a source device and a bit stream recording (BSR) device, numerous specific details are set forth m order to provide a thorough understanding of the present invention However, it will be recognized bv one skilled in the art that the present invention mav be practiced without these specific details or with equivalents thereof In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention
According to the present invention, the AV packet information is encrypted at the time when the packets are transmitted from the source device, and the cipher mode or encryption process that is used is altered according to an encryption mode indicator (EMI) code The EMI code of the present invention represents three conditions, a copy prohibition mode, a single generation copy allowance mode and an unrestricted mode The term "single generation copy" indicates that the original work may allow many copies to be made from it, but a copy of the original (e g , the one sent to the sink device) can be copied itself only once The EMI information indicating the selected cipher mode is stored in a packet header If the EMI information is corrupted on the receiving side, the sink (e g , receiving) device will be unable to acquire the correct AV information from the packets because the sink device will decrypt in a cipher mode different from the genuine cipher mode In one embodiment, the cipher mode includes an encryption process, a cipher key, and can include an initial value of a register
Moreover, depending upon whether the transmitting device and the sink device can understand the EMI information added to the information packet, the individual communications can be classified to use different cipher modes so that the transmitting device and the sink device can recognize the other device
EMI SECURE COMMUNICATION MODES
Figure 3 illustrates an exemplary system 100 of the many system configurations that are supported within the present invention System 100 includes an optional wireless transmitter 1 10 which is capable of communicating digital AV information representing a digital program via broadcast channel 115 In one embodiment, transmitter 1 10 can be a satellite broadcast unit In an alternative embodiment, transmission line 1 15 is not wireless, but a cable In this case, transmitter 1 10 is a land-based transmitter of a cable or pay-TV company
System 100 also includes a digital broadcast receiver unit 120 This unit 120 can also be called a set top box (STB) Herein, receiver unit 120 is called the source device 120 The source device 120 contains EMI circuitry 150 in accordance with the present invention to support a number of EMI communication modes which are descπbed further below Circuit 150 utilizes a different encryption mechanism for each EMI encryption mode The source unit 120 is an intelligent device and contains specialized circuitry for processing copy protection standards For instance, source unit 120 receives a digital program over channel 1 15 and this digital program can be encoded using copy control information (CCI information)
System 100 of Figure 3 also includes a sink device 130 which in this example is a bit stream recorder (BSR) unit 130 and is coupled to the source unit 120 using a serial interface 125 Although shown as a BSR device, sink unit 130 could also be any receiver unit shown in Figure 8 In many cases, the sink unit 130 is a relatively simple device and, to keep costs down, does not contain the full complement of specialized circuitry required to fully process copy protection standards For instance, sink unit 130 does not have the ability to decode CCI coded AV information However, it does contain EMI circuitry 160 in accordance with the present invention EMI circuitry 160 has the ability to decrypt AV information packets encrypted according to EMI codes Sink unit 130 is coupled to receive digital information from the source unit 120 over a seπal line 125 Digital information is passed over line 125 using the IEEE 1394 communication standard Moreover, this information is forwarded in digital data packets that contain header information in a header portion and AV information (e g , data) in a data portion
As descπbed further below, EMI circuits 150 and 160 of Figure 8 are implemented such that each contains two cipher circuits so that information transmitted over line 125 is encoded under at least two different encryption mechanisms, A and B In one embodiment, EMI circuit 160 also has two cipher circuits so that it can (if allowed) decrypt information received over line 125 in mode A or in mode B encryption Rather than using a BCI code, the present invention uses an EMI code placed within data packets of line 125 The EMI code, in addition to indicating the copy protection mode, also advantageously determines the encryption mode used in the data portion of the packet Therefore, the EMI circuit 160 within the sink unit 130 uses the EMI mode to select the proper decryption mechanism to decrypt the transmission received from line 125 Should be EMI code of the present invention be tampered with between the sink device 120 and the source device 130 (e g , by an intermediate intercept device), then EMI circuit 160, of the present invention, will select the wrong decryption mode In this instance, the original transmission will not be obtained by the sink device 130
There are three kinds of AV information packets which are transmitted over digital interface 125 They is copy free information, copy once information and copy prohibited information The streams have different security levels of copy protection in accordance with the present invention The manner in which copy protection is provided to each packet is called its EMI mode. As described below, in accordance with the present invention the EMI mode also indicates the mode of encryption that is applied to the AV information associated with the EMI mode.
The cipher or EMI modes used in accordance with the present invention are described as follows. EMI mode A is used to indicate that the packet data is copy prohibited. Under this mode A, AV information can only be rendered on a playback device (e.g., TV or monitor), but the AV information is not allowed to be recorded. EMI mode B is used to indicate that the AV information can be copied (e.g., recorded) only one time to allow a single generation copy. This mode B also called single generation copy allowance mode. EMI mode O is used when the AV information has no copy protection and therefore there is no copy limit. Mode O is also called unrestricted mode. For simplicity of description, no encryption is made for the mode O in the present embodiment. In the case of AV information in the copy control state allowing n number of copies (n>l), an extension can be made by defining the modes corresponding to the individual n-copies.
The EMI modes can be represented using a number of well known encoding techniques and can be represented using a register having at least two bits. In one particular embodiment of the present invention, a two bit register is used. Table I below illustrates exemplary coding numbers for each EMI mode. It is appreciated that the coding numbers selected within Table I are exemplary only and that any set of three unique numbers can be used.
Table I
EMI Mode Two Bit Number Description
Mode A 11 Copy Prohibition
Mode B 10 Copy Once
Mode O 00 No encryption Unrestricted
Reserved 01
It is appreciated that AV information received over digital interface 125 can include multiple programs. Each program can have its own copy security level. In this case, a copy prohibition stream (code 1 1) is a stream which includes at least one copy prohibited program. A copy once stream (code 10) is a stream that has no copy prohibited programs and includes at least one copy once program. With the particular example of a BSR sink device 130 (Figure 3), device 130 is able to record only AV information received in EMI mode B (or EMI mode O) and can only pass through (or reject) AV information received in EMI mode A
Figure 4 illustrates the fields that constitute a typical information packet 200 in accordance with the present invention that are sent from the source unit 120 to the sink unit 130 (Figure 3) Information packet 200 of Figure 4 contains an IEEE 1394 header section 230 because, in one embodiment, the data packets conform to the IEEE communication standard This header section 230 contains a data ength field, a tag field, a channel field, a tcode field and an sy field Aside from the tag and tcode fields, header 230 conforms to the well known IEEE standard and the other fields are defined therein The tag field indicates that the data field starts with a CIP header 240 The tcode field can be one of two predetermined values It is appreciated that a data stream means a stream of information on one 1394 isochronous channel Information packet 200 also contains a CIP header section 240 In accordance with the present invention, the CIP header section 240 contains an EMI field 210 that in one implementation is two bits wide and contains the EMI mode value as defined in Table I The EMI mode value corresponds to the particular secure communication mode associated with the data of the data field 220 of the section 250 As described further below, the EMI mode indicated within the EMI field 210 indicates (1) the particular secure communication mode selected (e g , mode A, mode B or mode O) and also (2) the particular type of encryption technique used for packet 200 It is appreciated that while the present invention encrypts the data portion 220 of packet 200 (if in EMI mode A or EMI mode B), the header sections 230 and 240 remain unencrypted when transmitted over the IEEE 1394 interface 125 (Figure 3)
EMI modes within field 210 indicate the copy control status of the data stream on the 1394 isochronous stream It is important to understand that the data stream in accordance with the present invention can consist of several video and/or audio programs and each of them can have a different copy control information associated with the program For instance, the MPEG transport stream output from a source unit can contain several programs, each of which can have a different level of copy protection The source device assigns the EMI value for the most restπctive program in the stream A bit stream recorder may or may not record the entire stream based on the EMI value Another type of recording device which is capable of processing each program in the stream individually and is also capable of interpreting copy control information associated with each program is called a format cognizant recording device A format cognizant recording device refers control information associated with each program to decide its action EMI CIRCUITRY OF THE PRESENT INVENTION
Figure 5 A illustrates a system 400 of the present invention having a source device 120 and a sink device 130 Figure 5A illustrates the EMI circuitry 150 of a typical source unit 120 in more detail Source unit 120 can be a set-top-box (STB) unit also called a broadcast receiver which contains many well known circuits (not shown for clarity) in addition to the EMI circuit 150 A receiver circuit 410 receives AV information in the form of data packets and performs any decryption required under CCI standards The result is forwarded over communication interface 430 and also to a de-multiplexer (de-mux) 414 using interface 413 Circuit 412 is an EMI mode select circuit and depending on the recovered CCI copy protection information will select either EMI mode A or EMI mode B if copy protection is required If no copy protection is required, then interface 413 is passed directly to interface 125 and EMI mode O (code "00") is inserted into EMI field 210 of the data packet
Assuming copy protection is required, select circuit 412 controls de-mux 414 via signals over line 426 If EMI mode A is selected, then the data packet from 413 is routed to encrypt unit A 418 which encrypts the data portion (e g , field 220) of the data packet according to a cipher key 416 and according to a first encryption technique within encryption unit A 418 Unit 418 also places the "1 1" code (EMI mode A) within the EMI mode field 210 of the data packet The result is then passed to multiplexer (mux) 422 which is also controlled by line 426 Mux 422 passes the output from encryption unit A 418 to interface 125 using the optional output driver 424 If EMI mode B is selected, then the data packet from 413 is routed to encrypt unit B 420 which encrypts the data portion (e g , field 220) of the data packet according to the key 416 and according to a second encryption technique within encryption unit B 420 Unit 420 also places the "10" code (EMI mode B) within the EMI mode field 210 of the data packet The result is then passed to multiplexer (mux) 422 which is also controlled by line 426 Mux 422 passes the output from encryption unit B 420 to interface 125 using the optional output driver 424 In this embodiment, two different encryption units are used and the encryptions are based on a common key value 416 to provide two encryption mechanisms As discussed further below, the key 416 can be established during a source-sink authentication process
Sink device 130 of Figure 5A contains many well known circuits (not shown for clarity) in addition to EMI circuit 160 EMI circuit 160 within the sink device 130 of Figure 5 A contains a decryption unit A 448 which can decrypt an encryption made bv encryption unit A 418, assuming cipher key 452 coincides with key 416 and also contains a decryption unit B 450 which can decrypt an encryption made by encryption unit B 420, assuming key 452 is correct The data packet of interface 125 is received by a de-multiplexer circuit 442 and also by an EMI mode extractor circuit 440 Circuit 440 extracts the header information from the received data packet and extracts the EMI field 210 from the header Depending on the EMI mode extracted circuit 440 controls signals over line 446 If EMI mode O is extracted, then the data packet over line 125 is directly coupled to the bit stream recording media 456 or is allowed to be directly output over line 470 without inhibition
If circuit 440 extracts EMI mode A, then the data packet from interface 125 is routed through de-mux 442 to decryption unit A 448 which decrypts the data portion of the data packet (using key 452) and forwards the result to mux 454 which is also controlled bv select line 446 Mux 454 routes the data packet from the output of decryption unit A 448 to the output line 470 only When the sink device 130 is a BSR device, it is not allowed to record an EMI mode A data packet, so recording to the BSR media 456 is prohibited in this case If circuit 440 extracts EMI mode B, then the data packet from interface 125 is routed through de-mux 442 to decryption unit B 450 which decrypts the data portion of the data packet, changes the EMI mode to EMI mode A, records the "1 1 " code (mode A) in the EMI field 210, and forwards the result to mux 454 which is also controlled by select line 446 Mux 454 routes the data packet from the output of decryption unit B 450 to the output line 470 and allows the BSR media 456 to record the data packet, now in EMI mode A When the sink device 130 is a BSR device, it is allowed to record an EMI mode B data packet only once, so this data packet is changed to an EMI mode A packet prior to recording to the BSR media 456 In this embodiment, two different decryption units are used and the decryption is based on a single cipher key 452
When the sink device 130 is a bit stream recording (BSR) device, it is not allowed to record EMI mode A encrypted data Therefore decrypt unit A for EMI mode A is not implemented in the BSR Figure 6A illustrates the block diagram 665 of an alternative embodiment of the EMI circuitry for a bit stream recording sink device 130 without the decrypt unit A In this embodiment, if the EMI extractor 440 detects mode A in the input 125 it stops the decrypt unit B 450 and stops the BSR recording unit 456
Circuit 400 of Figure 5 A prevents intermediate devices from compromising the copy protection m the following manner If an EMI mode A data packet is altered on line 125 to an EMI mode B data packet the sink device 130 will use the wrong decryption unit when attempting to recover the data The result becomes meaningless information recorded by BSR media 456 If an EMI mode A or an EMI mode B data packet from interface 125 is altered to an EMI mode O data packet, then sink device 130 will not perform any decryption and the result is not renderable
Figure 5B illustrates a system 500 of the present invention having a source device 120' and a sink device 130' Figure 5B illustrates the EMI circuitry 150' of a typical source unit 120' and EMI circuitry 160' of a typical sink unit 130'of an alternative embodiment of the present invention In this embodiment, a common encryption unit and a common decryption unit are used, but they receive different cipher keys (Key A, Key B) depending on the EMI mode selected, this provides the two encryption-decryption mechanisms
Source unit 120' of Figure 5B can be a set-top-box (STB) unit also called a broadcast receiver which contains many well known circuits (not shown for clarity) in addition to EMI circuit 150' A receiver circuit 510 receives AV information in the form of a data packet and performs any decryption required under CCI standards The result is forwarded over communication interface 512 (coupled to an EMI mode selected circuit 514) and also to an interface 513 Circuit 514 is an EMI mode select circuit and depending on the recovered CCI copy protection information will select either EMI mode A or EMI mode B, if copy protection is required If no copy protection is required, then interface 513 is passed directly to interface 125 and EMI mode O (code "00") is inserted into EMI field 210 of the data packet
Assuming copy protection is required, select circuit 514 controls the select line of multiplexer (mux) 516 Common key 524 is routed to hash circuit A 520 having a first hash function which generates a first cipher key (key A) at its output Key 524 is also routed to hash circuit B 522 having a second, different, hash function which generates a second cipher key (key B) at its output If EMI mode A is selected, then mux 516 selects key A to forward to common encryption unit 518 which encrypts the data portion (e g , field 220) of the data packet according to key A and according to a common encryption technique within encryption unit 518 Unit 518 also places the "11" code (EMI mode A) within the EMI mode field 210 of the data packet The result is then passed over interface 530 to an optional driver circuit 526 which outputs the data packet to interface 125
If EMI mode B is selected, then mux 516 of Figure 5B selects key B to forward to common encryption unit 518 which encrypts the data portion (e g field 220) of the data packet according to key B and according to the common encryption technique within encryption unit 518 Unit 518 also places the "10" code (EMI mode B) within the EMI mode field 210 of the data packet The result is then passed over interface 530 to an optional driver circuit 526 which outputs the data packet to interface 125 In this embodiment, two different keys (A and B) are used to alter the encryption process used in the single common encryption unit 518 As discussed below, the key 524 can be established during a source-sink authentication process After sharing a covert channel key, Kc, the source device 120' and the sink device 130' share work keys, A and B First, the source device 120' sends a random number Na to the sink device 130' The source device and the sink devices use internal EMI circuitry to compute the work keys (Key A and Key B) by
Key A = HKc(Na || Ca) key B = HKc(Na || Cb)
where Hkc a keyed hash function using a key Kc and Ca and Cb are constant and are licensing codes
Circuit 150' is advantageous because it only requires a single encryption unit 518 Although two hash function circuits 520, 522 are required, this additional circuitry is generally less than the circuitry eliminated by eliminating the second encryption unit This is particularly true if the hash functions are implemented in software Hash functions are readily implemented in software because the function needs to be determined only once for a given key
Sink device 130' of Figure 5B contains many well known circuits (not shown for clarity) in addition to EMI circuit 160' EMI circuit 160' within the sink device 130' contains a single common decryption unit 544 which can decrypt an encryption made by common encryption unit 518, assuming the corrected common key is supplied The data packet of interface 125 is received by an EMI mode extractor circuit 540 Circuit 540, like circuit 440, extracts the header information from the received data packet and extracts the EMI field 210 from the header Depending on the EMI mode extracted, circuit 540 controls the select line of mux 542 If EMI mode O is extracted by circuit 540, then the data packet over line 125 is directly coupled to the bit stream recording media 550 or is allowed to be directly output over line 570
Assuming copy protection modes are extracted EMI extraction circuit 540 controls the select line of multiplexer (mux) 542 Key 554 is routed to hash circuit A 546 having the first hash function which generates the first cipher key (kev A) at its output Key 554 is also routed to hash circuit B 548 having the second, different, hash function which generates the second cipher key (key B) at its output. If EMI mode A is extracted from the data packet, then mux 542 selects key A to forward to common decryption unit 544 which decrypts the data portion (e.g., field 220) of the data packet according to key A and according to a common decryption technique within decryption unit 544 Unit 544 also places the "1 1 " code (EMI mode A) within the EMI mode field 210 of the data packet. The result is routed to the output line 570 only. When the sink device 130' is a BSR device, it is not allowed to record an EMI mode A data packet, so recording to the BSR media 550 is prohibited in this case.
If EMI mode B is extracted by circuit 540, then mux 542 of Figure 5B selects key B to forward to common decryption unit 544 which decrypts the data portion (e.g., field 220) of the data packet according to key B and according to the common decryption technique within decryption unit 544 Unit 544 also places the "1 1 " code (EMI mode A) within the EMI mode field 210 of the data packet. The result now in EMI mode A is then passed over interface 552 to a BSR recording media 550 and optionally to an output interface 570 When the sink device 130' is a BSR device, it is allowed to record an EMI mode B data packet only once, so this data packet is changed to an EMI mode A packet prior to recording to the BSR media 550. In this embodiment, two different keys (A and B) are used to alter the decryption process used in the single common decryption unit 544 As discussed further below, the key 554 (same as 524) can be established during a source-sink authentication process. Circuit 160' is advantageous because it only requires a single decryption unit 544 Although two hash function circuits 546, 548 are required, this additional circuitry is generally less than the circuitry eliminated by eliminating the second decryption unit. Hash functions 546, 548 are readily implemented in software because the function needs to be determined only once for a given key.
When the sink device 130' is a bit stream recording (BSR) device, it is not allowed to record EMI mode A encrypted data. Therefore, hash A circuit for EMI mode A is not implemented in the BSR Figure 6B illustrates the block diagram 670 of an alternative embodiment of the EMI circuitry for a bit stream recording sink device 130' without the hash A circuit. In this embodiment, if the EMI extractor 540 detects mode A in the input 125, it stops the common decrypt unit 544 and stops the BSR recording unit 550
Circuit 500 of Figure 5A prevents intermediate devices from compromising the copy protection in the following manner. If an EMI mode A data packet is altered on line 125 to an EMI mode B data packet, the sink device 130' will use the wrong decryption key (between key A and key B) when attempting to recover the data The result is meaningless information recorded by BSR media 550 If an EMI mode A or an EMI mode B data packet from interface 125 is altered to an EMI mode O data packet, then sink device 130' will not perform any decryption and the result is not renderable
Figure 7 illustrates a flow diagram 700 of steps performed by the present invention with respect to system 400 of Figure 5A At step 710, authentication is performed so that sink device and source device recognized each other This process can be performed using various predetermined license and service keys Any of a number of well known authentication and secure key exchange processes can be used at step 710 in accordance with the present invention In the result, special codes are exchanged if authentication was successful and step 720 is entered If authentication failed, then at step 715, process 700 returns without any AV information exchanged
At step 720 of Figure 7, the source device 120 utilizes the special codes to send an encrypted key to the sink device 130 which decrypts the key At this point, key 416 and key 452 are established between the source and sink devices and these keys are of the same value At step 730, the source device 120 receives a data packet having a first copy protection mode (e g , using CCI modes) and translates this CCI mode into an EMI mode (e g , copy prohibited, copy once, unrestricted) At step 740, the circuit 150 places the proper EMI mode into the header of the received data packet and encrypts the data portion of the data packet using one of two possible encryption mechanisms according to the EMI mode This data packet is then forwarded over interface 125
At step 740 of Figure 7, the since device uses circuit 160 to extract the EMI mode and decrypt the data packet according to the EMI mode that was extracted One of two possible decryption mechanisms are used based on the EMI mode This information is recorded in EMI mode A (full protection) if EMI mode B was received If EMI mode A was received, then no recording is allowed At step 760, if more data packets are required, then process 700 returns to step 740 to process the next data packet Otherwise, process 700 returns
The operational procedure of the alternative embodiment of Figure 5B is similar to the above except different keys are used to provide the different encryption and decryption mechanisms of Figure 5B CLASSIFICATION OF DEVICES IN ACCORDANCE WITH THE PRESENT INVENTION
Figure 8 illustrates a number of different classes of devices that can be used in accordance with the present invention Also shown in Figure 8 are the types of AV information packets (classified by EMI mode) that can be received and transmitted by each device The dotted signal lines represent AV information packets in EMI mode B and the solid signal lines represent AV information packets in EMI mode A The first device class is device class A These devices include transmitting devices that can add the EMI code to their packet information and also include those devices that can receive CCI data An example is a set-box (STB) 120 which is able to receive a satellite broadcast (e g , in CCI format) and transmit the data over the IEEE 1394 bus As shown in Figure 8, the STB device 120 can generate AV transmission packets encrypted under either EMI mode A or EMI mode B The STD device 120 can also generate AV transmissions that are unrestricted Device 120 supplies AV information in EMI mode B as shown by output 626 and in EMI mode A as shown by output 628
The second device class is device class B These devices include receiving or sink devices that are capable of responding to the EMI information that is present within AV information packets An example device within class B is the format cognizant recorder device 630 This device 630 is able to properly decrypt the received AV information packets in any EMI mode, record the AV information using the IEEE 1394 standard format, record the EMI information added thereto and transmit the reproduced data using the IEEE 1394 standard format If the AV information received is oπginated in EMI mode B, when recorded it is altered to EMI mode A to prevent further copies Device 630 is able to receive AV information packets encrypted in EMI mode B 632 and in EMI mode A 634 but only can supply AV information encrypted in EMI mode A 636
The third device class is device class C These devices include receiving devices that are incapable of fully processing certain copy protection information (e g under CCI modes) because these devices lack the specialized circuitry required to fully process this copy protection information One example of class C is the bit stream recorder (BSR) device 130 of Figure 8 It is capable of receiving only AV information encrypted in EMI mode B via input 610 and is capable of supplying only AV information encrypted in EMI mode A via output 615 The BSR device 130 is capable of decrypting mode B encryption using the extracted EMI code and storing this information, if EMI mode B is received The BSR device 130 can also reproduce AV information and transmit this information in EMI mode A under the IEEE 1394 standard The fourth device class is device class D. These devices include receiving devices that can process EMI information which is added to the information packets. An example of a class D device is digital television 620. The digital TV set 620 is able to receive AV information encrypted in EMI mode B via input 622 and encrypted in EMI mode A via input 624, under the IEEE 1394 standard. The digital TV 620 is able to decrypt AV information from either EMI mode A or EMI mode B and render the AV information.
Encryption and decryption modes can be licensed by an entity depending on the functions which the entity wants to achieve. If the entity manufactures display devices, licenses for decryption of EMI mode A and EMI mode B are necessary. If the entity manufactures a BSR unit 130, decryption of EMI mode B and encryption for EMI mode A are necessary. EMI modes A and B can be combined with license keys and service keys, as described below with respect to one embodiment of the present invention.
EXEMPLARY SERVICE CLASSIFICATIONS IN ACCORDANCE WITH ONE EMBODIMENT OF THE PRESENT INVENTION
In one embodiment of the present invention, particular communication services are supported. In this embodiment, particular secrets (e.g., key codes) are defined depending on the type of service used and whether a device is a source or sink device. According to the above classifications of the transmitting devices and the receiving devices, the following indicates service classifications for data transmissions. Transmissions within service 1 include transmitting devices of Classes A, B, or C with receiving devices of Classes A, B, or C. Transmissions within service 2 include transmitting devices of Classes A, B, or C with receiving devices of Class D. Transmissions within service 3 include transmitting devices of Class D with receiving Devices of Classes A, B, or C.
Generally, under service 1, a source unit which recognizes CCI copy protection format sends AV information to a sink unit which also recognizes this CCI format (e.g., STD --> display, or, STB --> format cognizant recorder). Both source and sink are copy protection intelligent devices. Under service 2, a source unit which recognizes the CCI format sends AV information to a sink unit which does not recognize CCI format but is implemented to recognize the EMI codes in accordance with the present invention (e.g., STB --> BSR unit). The sink unit does not have the same level of copy protection intelligence as the source unit. Under service 3, a source unit that does not recognize CCI format sends AV information to a sink unit that recognizes CCI format (e g , DVHS --> Display)
In one embodiment of the present invention, secret codes (e g , key codes) for using the EMI modes A and B and the services 1, 2, and 3 are given (e g , licensed) to the devices of the individual classes enumerated above A key code or "secret" is used by the two devices for performing secure key transmissions duπng authentication, as described above In this manner, the keys that are described above and used for encryption and decryption can safely be transmitted between the source and sink devices
In the services 1, 2, and 3, different key codes are necessary for the transmitting devices and the receiving devices For example, the key code for the transmitting device of the service
1 is different from the key code for the receiving device Described here is the manner that the key codes are provided to the individual devices According to the table of Figure 9 there are eight key codes used in this embodiment of the present embodiment The device classifications can be further refined according to types of data such as MPEG or DV A pair including a service key and a license key is allocated to services 1, 2, and 3, respectively A source unit has a service key and a sink unit has the licensed key corresponding to its supported services Therefore, services 1, 2 and 3 are distinguished by service key or license key
For example, STB unit 120 can give service 1, 2 so STB unit 120 has service key 1 and
2 The DVHS 130 can receive service 2 and give service 3 so Dλ ΗS 130 has license key 2 and service key 3 Each service can be divided into sub services within it own service group A set of encryption mode(s), service mode(s) and license key(s) is given to a unit depending on the functions the device should have For instance, a display device 620 could have decryption EMI mode A and EMI mode B and license keys for services 1 and 3 The STB unit 120 could have encryption for EMI mode A and EMI mode B and service keys for service 1 and service 2 The DVΗS (BSR) unit 130 could have decryption for EMI mode B, encryption for EMI mode A and license key for service 2 and service key for service 3
According to Figure 9 the devices of Class A are required to have key codes for the transmitting devices of services 1 and 2 and key codes for EMI modes A and B and are provided key codes Secret IT, Secret IT, Secret 2T, Secret 2T, Secret A, and Secret B Likewise, the devices of Class B are required to have key codes for the receiving devices of service 1 and 3, a key code for the transmitting device of Service 1, and key codes for Modes A and B, and are provided key codes Secret 1R, Secret 1R, Secret 3R, Secret 3R, Secret A, and Secret B The devices of Class C are required to have key codes for the receiving devices of Services 1 and 3 and key codes for Modes A and B and are provided key codes Secret 1R Secret 1R, Secret 3R, Secret 3R, Secret A, and Secret B The devices of Class D are required to have a key code for the receiving device of Service 2 and a key code for the transmitting device of Service 3 and are provided key codes Secret 2R, Secret 3T, Secret A, and Secret B Typically, the use of Mode A only for the transmissions and the use of Mode B only for the receptions is required
OPERATION OF PRESENT INVENTION USING SERVICE KEYS
The following procedure describes the manner in which data packets are transmitted from a source device of class A to a sink device of class B acting as a receiving device The data packets are transmitted from source device to sink device and are recorded by the sink device
The source device at the transmission side generates Kseed as a data key for encrypting the data packets The source device safely delivers the data key Kseed to the sink device at the reception side using the secrets Secret IT and Secret 1R for the transmitting device and the receiving device of Service 1 Next, the source device makes an encryption Key A for Mode A and a cipher Key B for Mode B by employing Kseed, Secret A, and Secret B Specifically, calculations are made by using
Key A = h (Kseed | | Secret A) Key B = h (Kseed | | Secret B)
Where letter h designates the hash function, and the expression a | | b designate a bit connection of a and b
The source device reads the value of the CCI added to the data to be transmitted If the CCI indicates the copy inhibition, the data packet is encrypted together with the CCI by means of the cipher Key A for Mode A The EMI mode ("1 1 ") is stored in field 210 and the data packet is transmitted over the IEEE 1394 interface If the CCI indicates the single generation copy allowance, the data are encrypted together with the CCI by means of the cipher key B for Mode B, and the EMI mode ("10") is stored and packeted in the EMI mode field 210 of the data packet and the packet is transmitted over the IEEE 1394 interface If the CCI indicates no copy limit, the data packet is not encrypted but packeted The EMI mode is stored as "00," in field 210 and the packet is transmitted Therefore, what key the transmitting device uses to encrypt the data does not depend upon the service but is determined by the EMI mode added to the data
Like the source device, the sink device generates Key A and Key B from Kseed Secret A, and Secret B The EMI of the received packet is inspected by the sink device, and the data is decrypted by using the key A, if the EMI mode indicates Mode A, and by using key B if the EMI mode indicates Mode B Next, the EMI mode added to the decrypted data is inspected The data are not recorded if the EMI mode indicates the copy inhibition The EMI mode is changed, if it indicates the single generation copy allowance, into the copy inhibition and is recorded together with the data The EMI mode is recorded together with the data, if it indicates no copy limit
Described next is the processing for the case the transmitting device is the of class a whereas the receiving device is of class d As in the foregoing procedure the source device delivers the Kseed safely to the sink device However, the secrets to be used here are Secret 2T and Secret 2R The source device generates the keys Key A and Key B, as described above, and encrypts the data in dependence upon the EMI mode added to the data The source device stores the proper EMI in the packet header and transmits it
The sink device generates the key B in a manner similar to that of source device Assume the sink device is inhibited to use Mode A for receptions by the license conditions so that it does not generate key A The sink device inspects the EMI mode of the received packet The sink device discards the packet if the EMI mode indicates Mode A If the EMI mode indicates Mode B, the sink device decrypts the data by means of the kev B and records the packets At this time, the information indicating that the data have been encrypted in mode B is recorded together with the data If the EMI mode indicates 00, the sink device records the data as they are At this time, the information indicating that the data have not been encrypted is recorded together with the data
The preferred embodiment of the present invention, a method and system for providing secure transmission of copy protected information between a source device and a bit stream recording (BSR) device, is thus descπbed While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims

Claims

1. A system for transferring information, said system comprising: a source device for encoding an encryption mode identifier (EMI) code into an information packet and for transmitting said information packet over a communication interface, said source device comprising: a first encryption circuit for encrypting data of said information packet provided said EMI code indicates a first mode; and a second encryption circuit for encrypting said data of said information packet provided said EMI code indicates a second mode; and a sink device for receiving said information packet from said communication interface, said sink device comprising: an extractor circuit for extracting said EMI code from said information packet; and a second decryption circuit for decrypting said data of said information packet in response to said extractor circuit indicating that said EMI code is of said second mode; and wherein said first mode is a copy prohibition mode indicating that said information packet is not to be reproduced by said sink device and wherein said second mode is a copy once inhibition mode indicating that said information packet is not to be reproduced more than once by said sink device.
2. A system as described in Claim 1 wherein said sink device further comprises a first decryption circuit for decrypting said data of said information packet in response to said extractor circuit indicating that said EMI code is of said first mode.
3. A system as described in Claim 2 wherein said first encryption circuit, said second encryption circuit, said first decryption circuit and said second decryption circuit are coupled to receive a same cipher key.
4. A system for transferring information, said system comprising: a source device for encoding an encryption mode identifier (EMI) code into an information packet and for transmitting said information packet over a communication interface, said source device comprising: a common encryption circuit for encrypting data of said information packet based on a first key if said EMI code indicates a first mode, and wherein said common encryption circuit is also for encrypting data of said information packet based on a second key if said EMI code indicates a second mode; and a sink device for receiving said information packet from said communication interface, said sink device comprising: an extractor circuit for extracting said EMI code from said information packet; and a common decryption circuit for decrypting said data of said information packet using said second key in response to said extractor circuit indicating that said
EMI code is of said second mode; and wherein said first mode is a copy prohibition mode indicating that said information packet is not to be reproduced by said sink device and wherein said second mode is a copy once inhibition mode indicating that said information packet is not to be reproduced more than once by said sink device.
5. A system as described in Claim 1 or 4 wherein said sink device is a bit stream recording device and wherein said sink device further comprises a recording media for recording said information packet provided said EMI code is of said second mode and wherein said EMI code of said information packet is altered to said first mode by said sink device upon recording onto said recording media.
6. A system as described in Claim 4 wherein said common decryption circuit of said sink device is also for decrypting said data of said information packet using said first key in response to said extractor circuit indicating that said EMI code is of said first mode.
7. A system as described in Claim 2 or 6 wherein said communication interface is a serial communication interface conforming to the IEEE 1394 communication standard and wherein said information packet is a digital information packet.
8. A system as described in Claim 2 or 6 wherein said source device is a broadcast receiver device and further comprises a receiver circuit for receiving an information packet encoded with CCI information and extracting a copy protection code therefrom and wherein said sink device is unable to process an information packet encoded with CCI information.
9. A system as described in Claim 2 or 6 wherein said information packet represents a portion of a digital audio/visual program.
10. A system as described in Claim 6 wherein said source device and said sink device each comprise: a first hash circuit for generating said first key based on a common key; and a second hash circuit for generating said second key based on said common key and wherein said common key is transferred between said sink device and said source device before said information packet is received by said sink device.
11. A method of transferring information that contains copy protection modes comprising the steps of: a source device receiving an information packet having a copy protection mode; said source device storing an encryption mode indicator (EMI) code into a header of said information packet depending on said copy protection mode; said source device using a first encryption mechanism to encrypt data of said information packet if said EMI code is of a first mode; said source device using a second encryption mechanism to encrypt said data of said information packet if said EMI code is of a second mode; said source device not encrypting said data of said information packet if said EMI code is of a third mode; and said source device transmitting said information packet to a sink device wherein said first mode is a copy prohibition mode indicating that said information packet is not to be reproduced by said sink device, said second mode is a copy once inhibition mode indicating that said information packet is not to be reproduced more than once by said sink device and said third mode is an unrestricted mode indicating that said information packet can be freely reproduced by said sink device.
12. A method as described in Claim 11 further comprising the steps of: said sink device receiving said information packet and extracting said EMI code therefrom; said sink device decrypting said data of said information packet using a first decryption mechanism if said EMI code is of said first mode; said sink device decrypting said data of said information packet using a second decryption mechanism if said EMI code is of said second mode; and said sink device not decrypting said data of said information packet if said EMI code is of said third mode.
13. A method as described in Claim 12 further comprising the step of: said sink device changing said EMI code from said second mode to said first mode and storing the new EMI code into said information packet; and said sink device recording said information packet.
14. A method as described in Claim 12 wherein said step of said source device receiving an information packet having a copy protection mode includes the step of said source device translating said information packet having encoded CCI information to extract said copy protection mode.
15. A method as described in Claim 12 wherein said information packet is a digital representation of a portion of an audio/visual program.
16. A method as described in Claim 12 wherein said source device is a broadcast receiver device and wherein said sink device is a bit stream recorder.
PCT/US1998/022126 1997-10-24 1998-10-19 A method and a system for transferring information using an encryption mode indicator WO1999022372A1 (en)

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CA002308141A CA2308141C (en) 1997-10-24 1998-10-19 A method and a system for transferring information using an encryption mode indicator
DE69803394T DE69803394T2 (en) 1997-10-24 1998-10-19 METHOD AND SYSTEM FOR TRANSMITTING INFORMATION WITH ENCRYPTION MODE INDICATOR
AU11035/99A AU1103599A (en) 1997-10-24 1998-10-19 A method and a system for transferring information using an encryption mode indicator
EP98953748A EP1012840B1 (en) 1997-10-24 1998-10-19 A method and a system for transferring information using an encryption mode indicator
JP2000518385A JP4185248B2 (en) 1997-10-24 1998-10-19 Transmission system and transmission method
AT98953748T ATE211575T1 (en) 1997-10-24 1998-10-19 METHOD AND SYSTEM FOR INFORMATION TRANSMISSION WITH ENCRYPTION MODE INDICATOR
KR10-2000-7004285A KR100533225B1 (en) 1997-10-24 1998-10-19 A method and a system for transferring information using an encryption mode indicator

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EP1012840B1 (en) 2002-01-02
US6223285B1 (en) 2001-04-24
DE69803394D1 (en) 2002-02-28
JP4185248B2 (en) 2008-11-26
JP2001521261A (en) 2001-11-06
KR100533225B1 (en) 2005-12-05
ATE211575T1 (en) 2002-01-15
AU1103599A (en) 1999-05-17
KR20010031296A (en) 2001-04-16
DE69803394T2 (en) 2002-08-29
CA2308141C (en) 2004-05-11
US7177427B1 (en) 2007-02-13
TW406260B (en) 2000-09-21
CA2308141A1 (en) 1999-05-06

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