WO2010025748A1

WO2010025748A1 - Method and network node for handling an electronic message with change of original sender identity

Info

Publication number: WO2010025748A1
Application number: PCT/EP2008/007234
Authority: WO
Inventors: Jos Den Hartog
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2008-09-04
Filing date: 2008-09-04
Publication date: 2010-03-11

Abstract

The present invention relates to a method for handling an electronic message in a communication network comprising a network node. A network node executes the steps of receiving the electronic message comprising an original sender identity of an original sender and a destination identity of a destination, changing the original sender identity in the electronic message into a different identity, signing the electronic message by means of a private key of the different identity, sending the electronic message to the destination.

Description

METHOD AND NETWORK NODE FOR HANDLING AN ELECTRONIC MESSAGE WITH CHANGE OF ORIGINAL SENDER IDENTITY

Technical Field

The present invention relates generally to electronic communication and, more specifically, to electronic message transfer between a sender and a destination in a communication network, wherein in an electronic message comprising an original sender identity of an original sender and a destination identity of a destination, the original sender identity in the electronic message is changed.

Background

In communication networks, several features can be applied to communications. For example, in some Virtual Private Networks a service is available, which replaces the calling party identification by a different identity. The name of such a service could be called "Different Number Presentation". Such service can relate to any communication service that has a sender identification (sender-id), such as a telephony service, e-mail service.

In sending electronic messages like e-mail, encryption can be used to protect and sign an electronic message by encrypting the electronic message.

Public key cryptography can be used for protecting and signing electronic messages. To be able to use public key cryptography, at least one key- pair must be generated, i.e. a public and a private key. The private key is stored on the sender's and/or recipient's own computer or mobile phone, wherein the public key is stored in a trusted public directory accessible by the sender and/or the recipients.

Public cryptography comprises public key encryption and digital signature. When public key encryption is used an electronic message encrypted with a recipient's public key cannot be decrypted by anyone except the recipient possessing the corresponding private key. This type of encryption is used to ensure confidentiality. When digital signature is used an electronic message signed with a sender's private key can be verified by anyone who has access to the sender's public key, thereby proving that the sender signed it and that the electronic message has not been tampered with. This is used to ensure authenticity. Signing an electronic message with a digital signature using public key cryptography works as follows. The sender signs an electronic message with the private key and sends the electronic message. The receiver receives a signed electronic message, e.g. an e-mail from user@domain.xx, and interrogates a public directory for the public key of the sender. Using this public key, the receiver can verify the electronic message. By verifying the electronic message using the public key of the sender, it is guaranteed that the e-mail has been signed using the private key of the sender. Because the private key of the sender is only available for the sender, it is guaranteed that the sender has sent this e-mail. If an identity changing service like "Different Number Presentation" is used for sending electronic messages between an original sender and a destination, in which the original sender is for example associated to a group like a company, an association, etc., an original sender identity in the electronic message is replaced into a different identity like "no-reply@domain.xx" or "main@domain.xx". A problem of using an identity changing service is that the original sender no longer can use its private key for signing an electronic message sent through a communication network to a destination, as the receiver of the electronic message cannot identify the true or original sender identity and the corresponding public key belonging to the sender identity.

Summary

An object of the present invention is to provide a method for handling an electronic message in a communication network, wherein an original sender identity of an original sender can be changed into a different identity.

Another object of the invention is to provide a network node for handling an electronic message in a communication network wherein an original sender identity of an original sender can be changed into a different identity.

In a first aspect, the invention provides a method for handling an electronic message in a communication network, comprising a network node wherein the network node executes the steps of receiving the electronic message comprising an original sender identity of an original sender and a destination identity of a destination, changing the original sender identity in the electronic message into a different identity, signing the electronic message by means of a private key of the different identity and sending the electronic message to the destination

The method for handling an electronic message according to the invention makes it possible to use both an identity changing service and digital signatures in the same communication of an electronic message through a communication network, like e.g. the Internet. A network node according to the present invention is a computer such as e.g. a mobile phone, or a personal computer, or a network node such as an electronic message server. The receiving step in the method according to the present invention includes that the electronic message is prepared by an original sender on a network node like a personal computer and a program running on the same network node, e.g. the same personal computer, receives such a prepared electronic message for changing the identity. After changing the original sender identity in the electronic message, such as user@domain.xx, into a different identity, for example "main@domain.xx", a private key of the different identity is used for signing the electronic message of the original sender before sending it to a destination, i.e. a receiver. The different identity has at least one private-public key pair (for e.g. "main@domain.xx") and this public key is stored in a trusted public database. The destination will receive an electronic message, e.g. an email from "main@domain.xx", which is signed with the private key of "main@domain.xx". By successful verifying such an electronic message using the public key of the different identity, e.g. "main@domain.xx", the destination has the guarantee, that the electronic message has been signed and sent by the different identity e.g. by "main@domain.xx".

With an electronic message any data containing electronic message is comprised which can be created with a mobile telephone, computer, etc., and of which its content can be signed and/or encrypted. An electronic message can be an e-mail with or without attachments, a Short electronic Message Service SMS, a Multimedia electronic Message Service MMS, or any other data file like pictures or music etc. sent over a communication network.

In an example of the method according to the invention, the electronic message is signed with the private key of the original sender, and wherein the network node executes the steps of verifying the signed electronic message with a public key of the original sender, signing the electronic message with the private key of the different identity and sending the signed electronic message to the destination. When the original sender identity is changed into the different identity, it is checked in the network node whether the electronic message is signed. Public keys of the original sender are stored in a database. If the electronic message from the original sender is signed, the electronic message is first verified in the network node by using the public key of the original sender. After the electronic message to be sent to the destination is signed by means of the private key of the different identity as described above, the signed electronic message is sent to the destination such that the destination can verify the electronic message using the public key of the different identity. Further, said original sender can be associated to a group, e.g. the original sender is an employee of a company, wherein the original sender identity of the original sender in the electronic message to be sent to the destination is changed into a group identity.

In another example of the method according to the invention, an identification of the electronic message sent from the original sender and the original sender identity of the original sender are recorded for sending a reply electronic message from the destination to the original sender.

As the original sender is unknown to the destination, the destination can only reply to the group or the identity known. By recording an identification of the electronic message sent from the original sender and the original sender identity a reply electronic message from the destination can be sent to the original sender.

In another example of the method according to the present invention, the communication network is Internet, Intranet, Internet Protocol Multimedia Subsystem Network, IMS, Global System for Mobile communication, GSM, Intelligent Network, IN, and/or a Virtual Private Network, VPN.

The method according to the present invention can be used in any of the above mentioned networks. An intranet is a private computer network that uses Internet protocols and network connectivity to securely share part of an organization's information or operations with e.g. its employees. Changing the identity of the original sender and signing with a private key of a different identity is performed in a network node within an intranet or a network node within a public network before sending the electronic message through the (public) Internet or VPN to a receiving destination. A Virtual Private Network (VPN) is mainly used to separate the traffic of different user communities over an underlying network, e.g. the Internet, with strong security features. The Internet Protocol Multimedia Subsystem (IMS) is an architectural frame for delivering internet protocol multimedia to mobile users. The Global System for Mobile communication (GSM) is a cellular network, which means that mobile phones are able to connect to it by searching for cells in the immediate vicinity. The intelligent Network (IN) is a network architecture intended both for fixed as well as mobile telecom networks.

In a further example of the method according to the invention, before or after signing with said private key of said different identity the electronic message is encrypted with the public key of the destination. To achieve authentication, non-repudiation, and confidentiality, the electronic message of the original sender is in a first step signed with the private key of the original sender, then in a second step before or after changing the original sender identity into a different identity, the electronic message is verified by means of the public key of the original sender. In a third step the electronic message with the different identity, e.g. a group identity, is signed by means of the private key of the different identity. For confidentiality a further encryption step is performed with the destination's public key on the electronic message to be sent to the destination. After receiving said electronic message the destination uses the public key of the different for a verifying step and its private key for further decryption of the electronic message or vice versa.

In a second aspect the present invention provides a network node for handling an electronic message in a communication network, the network node comprises an identity changing unit for changing the original sender identity of an original sender in an electronic message into a different identity, wherein the network node further comprises an encryption unit for signing the electronic message with a private key of the different identity before sending the signed electronic message to the destination.

Using the network node according to the invention for handling electronic messages makes it possible to use both a different identity and a signature in the same communication of an electronic message through a communication network. A network node according to the present invention is a computer such as e.g. a mobile phone, or a personal computer, or an electronic message server.

In an example of the network node according to the invention, the network node further comprises a decrypting unit for verifying a signed electronic message to be sent to a destination with a public key of an original sender before signing the electronic message by means of the encryption unit for sending the signed electronic message to the destination. If an electronic message from the original sender is signed, the electronic message first has to be verified by the decrypting unit of the network node. After the electronic message to be sent to the destination is signed by the encryption unit with the private key of the different identity, e.g. a group identity, the signed electronic message is sent to the destination such that the destination is able to verify the electronic message using the public key of the different identity.

According to another example of the invention, the network node comprises means to access a database for recording an identification of the electronic message and the original sender identity, wherein by means of the database the network node is adapted to send a reply electronic message from the destination to the original sender.

As the original sender is unknown to the destination, the destination can only reply to the different identity known. The network node uses a database to record all electronic messages sent by the network node between a original sender and a destination, such that the network node by means of the database is able to send the reply electronic message from the destination to the original sender, if the reply message contains enough information to link it to the original message.

If such a reply electronic message is signed by means of a private key of the destination, such reply electronic message is verified by means of a public key of the destination. This verifying step is performed with the network node, such as a message server in the communication network or with a network node such as a personal computer used by the original sender. This verifying step can be done with the network node in the form of a personal computer used by the original sender, as the identity of the destination is known to the original sender such that the original sender is able to find the public key for verifying the reply electronic message.

In addition, the encryption unit of the network node can also use a public key of the destination for a encryption step of the electronic message.

The identity changing unit, the encryption unit, and the decryption unit can be either implemented as software or as hardware or as a combination of software and hardware in the network node according to the present invention.

The invention will now be explained, in a non-limiting fashion, in more detail with reference to appended figures illustrating examples of the invention.

Brief description of the Drawings

The invention is described in detail with reference to the following figures.

Figure 1 shows a block diagram of a method according to the present invention.

Figure 2 shows a schematic view of clients and a network node according to the present invention.

Figure 3 shows a schematic view of a network node according to the present invention.

Detailed Description

The invention will now be described with reference to the figures. The depicted lines and arrows between the elements represent connections between these elements. The term connection refers to a functional connection and not necessarily to a physical connection.

Figure 1 shows a flow diagram of the main steps of a preferred embodiment of a method according to the present invention. Before starting the method according the present invention, an electronic message comprising an original sender identity of an original sender and a destination identity of a destination, e.g. an e-mail, is prepared for sending to a destination. For example, if the original sender is associated to a group, e.g. a company or a association having the policy that for all or specific outgoing electronic messages only a different identity will be communicated to other parties, a problem exists in that the original sender no longer can use a digital signature for an electronic message sent through a communication network to a destination, as the receiver or the destination of the electronic message cannot identify the true or original sender identity and the corresponding public key belonging to the sender identity. In the method according to the present invention the network node solves this problem by performing the following steps such that both an identity changing service and digital signatures in the same communication of an electronic message through a communication network can to be used: step 100: receiving the electronic message comprising an original sender identity of an original sender and a destination identity of a destination, step 101 : changing the original sender identity in the electronic message into a different identity, step 102: signing the electronic message by means of a private key of the different identity, step 103: sending the electronic message to the destination.

If the electronic message of the original sender is signed by means of a private key of the original sender, before step 100, it is necessary that before or after changing the identity of the original sender in a different identity (step 101 ), the electronic message is verified in the network node by means of the public key of the original sender.

When the electronic message is received by the destination, it can be verified by using the public key of the different identity.

Figure 2 shows clients 3, 8 and a network node 9 according to the present invention for handling an electronic message, like e-mail, SMS, and/or MMS between an original sender and a destination in a communication network 1 , e.g. a Virtual Private Network or a combination of networks such as a Intranet with the Internet.

A mail client 3 of a original sender is provided on a first communication device, such as a personal computer or a mobile phone for sending and receiving electronic messages.

When sending for example an e-mail, signatures and/or encryption can be used to sign and encrypt the content of the e-mail. For signing and protecting the content of an e-mail a public and a private key pair can be used. The key-pair is generated beforehand by means of a key generator 5. The private key is stored in a first memory 6 of the first communication device, the public key is stored in a trusted public directory 7.

E-mail of the original sender can be signed with the private key stored in a first memory of the first communication device. Such an signed e-mail is sent through a communication network 1 to a mail client 8 of a destination by means of network node 9 like an electronic message server 9.

An electronic message server 9 according to the present invention comprises an identity changing unit 11 for changing the identity of the original sender in the e-mail of the original sender. The identity changing unit 11 replaces the content in the from field of an e-mail of the original sender and changes the original sender identity into a different identity, for example a group identity. Further, it checks whether the content of the e-mail is signed. If the e-mail is signed, the public key of the original sender is used to verify the e-mail, which public key is stored in a trusted public directory 7.

For securely sending this verified e-mail, another public and private key pair is used. This pair is generated by means of a second key generator 13. This private key is stored in a memory 15 of the message server 9, and the public key is stored in a trusted public directory 17. Then, the e-mail is signed with the private key of the different identity stored in the memory of the message server 9, and the signed e-mail is sent by a communication unit 18 of the server 9 to the e-mail client 8 of the destination. The communication unit 18 of the server 9 provides communication channels to the VPN network and/or an intranet network.

The mail client 8 of the destination will hereafter receive an e-mail having a different identity, e.g. a group identity from "main@domain.xx", which is signed with the private key of the group identity. After receiving the signed e-mail from "main@domain.xx", this e-mail is verified by using the public key of "main@domain.xx". Because the e-mail can only be verified using the public key of the group identity, it is guaranteed that the e-mail has been signed using the private key of the group identity. Because this private key is only available to the group identity, it is guaranteed that the group identity has sent this e-mail.

Alternatively, the electronic message server 9 is connected to a database 20 shown in figure 2 by interfaces (not shown) that records identification of e-mails sent from the original sender to the destination. If the destination sends a reply e-mail to "main@domain.xx" as the address of the original sender is unknown to the destination, then this database is used by the communication unit 18 of message server 9 to link this reply e-mail to the original sender and to send or forward this reply e-mail to the original sender. The reply e-mail can be signed with a private key of the destination. As the original sender knows the identity of the destination, the public key of the destination can be used to verify the reply e-mail. However, it is possible that the e-mail has already been verified with the decryption unit 23 and that the verified reply e-mail is sent to the original sender.

Figure 3 shows a schematic view of an electronic message server 9 according to the present invention.

In addition to the identity changing unit 11 as explained above, the message server 9 comprises an encryption unit 21 using the private key stored in memory 15 for signing an e-mail of a original sender before sending this e-mail to the destination by means of the communication unit 18, interfaces 27, 29 and the communication network 1 in this example a Virtual Private Network (VPN). If an e- mail of the original sender is signed with the private key of the original sender, then the decryption unit 23 communicates by means of the communication unit 18 to the public directory 7, wherein after retrieving the public key of the original sender the e- mail is verified by means of the decryption unit 23. Encryption unit 21 can also use as an extra security measure the public key of the destination for encrypting the email to be sent to the destination to assure confidentiality.

The network node according to the present invention is shown in figures 2 and 3 as an electronic message server 9. However, it is within the scope of the present invention that the network node is formed by a mobile device or a computer like a personal computer on which mail client 3 is running and that the steps mentioned in the method according to the present invention containing the features of claim 1 are performed within this computer before sending the electronic message signed by a different identity to the destination, e.g. mail client 8 through a communication network 1.

The invention is not restricted to the examples disclosed above and illustrated in the drawings.

The identity changing unit, the encryption unit, and the decryption unit can be either implemented as software or as hardware or as a combination of software and hardware in the network node according to he present invention.

Claims

1. A method for handling an electronic message in a communication network comprising a network node, wherein the network node executes the steps of:

- receiving the electronic message (100) comprising an original sender identity of an original sender and a destination identity of a destination,

- changing the original sender identity (101) in the electronic message into a different identity, characterized by

- signing the electronic message (102) by means of a private key of the different identity (102),

- sending the electronic message to the destination (103).

2. The method according to claim 1 , wherein the destination verifies the signed electronic message using a public key of the different identity.

3. The method according to any one of the preceding claims, wherein the electronic message is signed with the private key of the original sender, and wherein the network node executes the steps of:

- verifying the signed electronic message with a public key of the original sender, and

- signing the electronic message with the private key of the different identity

- sending the signed electronic message to the destination.

4. The method according to any one of the preceding claims, wherein the original sender is associated to a group wherein the original sender identity of the original sender in the electronic message to be sent to the destination is changed into a group identity.

5. The method according to any one of the preceding claims, wherein an identification of the electronic message sent from the original sender and the original sender identity of the original sender are recorded for sending a reply electronic message from the destination to the original sender.

6. The method according to any one of the preceding claims, wherein the communication network is Internet, Intranet, Internet Protocol Multimedia Subsystem Network, IMS, Global System for Mobile communication, GSM, Intelligent Network, IN, and/or a Virtual Private Network, VPN.

7. The method according to any one of the preceding claims, wherein the electronic message is an email, Short Electronic message Service, SMS or Multimedia Electronic message Service, MMS.

8. The method according to any one of the preceding claims, wherein before or after signing with the private key of the different identity the electronic message is encrypted with the public key of the destination.

9. A network node (9) for handling an electronic message in a communication network, the network node (9) comprises an identity changing unit

(11) for changing the original sender identity of an original sender in an electronic message into a different identity, characterized in that the node further comprises an encryption unit (21) for signing the electronic message with a private key of the different identity before sending the signed electronic message to the destination.

10. The network node (9) according to claim 9, wherein the node further comprises a decrypting unit (23) for verifying a signed electronic message to be sent to a destination with a public key of an original sender before signing the electronic message by means of the encryption unit for sending the signed electronic message to the destination.

11. The network node (9) according to claim 9 or 10, wherein the node comprises means to access a database for recording an identification of the electronic message and the original sender identity, wherein by means of the database the node is adapted to send a reply electronic message from the destination to the original sender.

12. The network node (9) according to any one of the preceding claims 9-11 , wherein the communication network is Internet, Intranet, Internet Protocol Multimedia Subsystem Network, IMS, Global System for Mobile, GSM, communication, Intelligent Network, IN, and/or a Virtual Private Network, VPN.

13. The network node (9) according to any one of the preceding claims 9-12, wherein the electronic message is an email, Short Electronic message

Service, SMS or Multimedia Electronic message Service, MMS.

14. The network node (9) according to any one of the preceding claims 9-13, wherein the identity changing unit is adapted to change the original sender identity of an original sender in an electronic message into a group identity.

15. The network node (9) according to any one of the preceding claims 10-14, wherein the encryption unit is adapted to use a public key of the destination for encrypting the electronic message.to be sent to the destination.