WO2014009574A1

WO2014009574A1 - Security system and method for nfc communications.

Info

Publication number: WO2014009574A1
Application number: PCT/ES2012/070530
Authority: WO
Inventors: Carlos PIQUERAS ALONSO; El Bachir EL ACHHAB; Luis CABEZAS CASTILLO
Original assignee: Life Quality Technology, S.L.
Priority date: 2012-07-12
Filing date: 2012-07-12
Publication date: 2014-01-16

Abstract

The invention relates to a security system and method for NFC communications. Said system comprises an NFC terminal (1) and an NFC mobile device (3), one of which acts as the master terminal (7) and the other as the slave terminal (8), each one having a substantially identical NFC transceiver circuit (2). The master terminal (7) obtains (100) the induced voltage value (IV) in the NFC transceiver circuit thereof as a result of the electromagnetic induction (101) produced by a mutual approaching, encrypts (105) the original data (DATA) using an encryption key (MK), obtaining encrypted data (DT), and transmits (104, 106), to the slave terminal (8), the encrypted data (DT) and a value (Cft), as a function (f) of the encryption key (MK) and the induced voltage value (IV). The slave terminal (8) obtains (107, 109) the induced voltage value (IV) in the NFC transceiver circuit (2) thereof and the encryption key (MK), from the value (Cft) received and the induced voltage value (IV), and decrypts (108) the encrypted data (DT) received using the encryption key (MK), obtaining the original data (DATA).

Description

Security system and method for NFC communications

FIELD OF THE INVENTION

The present invention is related to the security of NFC (Near Field Communlcation) technology in particular, a hardware design is presented that allows resolving existing vulnerabilities in systems based on that technology.

BACKGROUND OF THE INVENTION

NFC technology allows two devices that are very close to each other to communicate, even closer than with Bluetooth. The operating range is below the 20 cm range and uses the NFCIP-1 protocol that can operate at different speeds of up to 848 Kbit / s. It works within the 13.56 Hz band, which means that it is not subject to any restrictions and no license is required to use it, which is a great advantage that differentiates this technology with other technologies used for it. finish. Within its apparent limitations the system is perfect precisely for that, to establish a communication between two devices whose only requirement to produce is that both are close.

The first uses of NFC technology are closely linked to mobile phones due to its ubiquity and the fact that it is the only device we all need to carry everywhere. Therefore, the applications that this technology can have are many and almost all of them need a security system that allows operations to be carried out safely. NFC technology {Near Field Communication) is not something new in itself but offers new features, highlighting the short distance to which the devices that carry out the communication must be. It has a multitude of applications that can be interesting such as bank transactions through "micropayment", as well as access to information and payment of different services. These applications among others that make use of NFC need a security system that guarantees a secure exchange of information since known attacks - in other similar technologies could have an impact on the progress of NFC. The most common attacks are:

• "Sniffing" or "eavesdropplng" is a more common attack on wireless communication systems. Through a specially prepared antenna, and A specific team, an attacker can listen to the data that communicates between two devices.

• Data corruption: this type of attack is a type of denial of the characteristics of the signal, for example the amplitude of the modulation of the signal and the type of coding.

• Modification of data: this type of attack is similar to the previous one, but the intention, instead of making a distributed denial of service (DDoS) attack, is to modify data by making it still valid. . This type of attack depends to a large extent on characteristics such as the amplitude of signal modulation and the type of coding, being more feasible in anchester coding than in MÜIer:

• "Main-in-the-Middie" (MitM or intermediary) in an attack in which the two parties that communicate are deceived thinking that they communicate with each other safely while the attacker is between them communicating with both.

Those are some of the ways in which NFC security could be compromised. The security in NFC is based on the fact that communication is carried out at close range since this fact reduces the possibility of any threat but does not guarantee complete security.

Any emerging technology that goes on the market becomes the target of the "cybercrime" mafias, so a system so new and, even so little known, must be studied thoroughly to avoid fraud risks. For the reasons mentioned above it is essential to provide robustness, in a matter of safety, to NFC technology. The security mechanisms addressed so far in NFC technology are mainly based on software design, which always has a backdoor through which it can continue to attack. That is why the present solution is more robust, since it also implies a hardware design, much more difficult to attack and that also does not make information processing so complex, which always takes time and energy consumption.

DESCRIPTION OF THE INVENTION

The present invention relates to a system and a security method for NFC communications. The system comprises an NFC terminal and an NFC mobile device, any one of them acting in an NFC communication as a terminal teacher and the other as it ends! slave. Both the NFC terminal and the NFC mobile device have a substantially identical NFC transceiver circuit. The master terminal is configured to:

- before the electromagnetic induction produced by a mutual approach, obtain the voltage value induced in its NFC transceiver circuit;

- encrypt the original data with an encryption key, obtaining encrypted data;

- transmit to the slave terminal, through the NFC transceiver circuit, a value that is a function of the encryption key and the induced voltage value;

- transmit the encrypted data to the slave terminal via the NFC transceiver circuit;

For its part, the slave terminal is configured to:

- obtain the voltage value induced in its NFC transceiver circuit produced by mutual approach;

- obtain, from the received value and the induced voltage value, the encryption key;

- decrypt, using the encryption key, the encrypted data received, obtaining the original data. In a preferred embodiment each NFC transceiver circuit comprises data processing means, a magnetic field generator and a magnetic field detector.

The NFC transceiver circuit can be integrated in the corresponding terminal or it can be external to it, being connected to it by means of a connect.

Another aspect of the present invention relates to a security method for NFC communications between an NFC terminal and an NFC mobile device having a substantially identical NFC transceiver circuit, any one of them acting in an NFC communication as a master terminal and the other As a slave terminal. The method comprises:

- before the electromagnetic induction produced by a mutual approach, obtain the voltage value induced in the NFC transceiver circuit of the master terminal;

- encrypt with an encryption key the original data to be transmitted by the master terminal, obtaining encrypted data; - transmit to the slave terminal, through the NFC transceiver circuit of the master terminal, a value that is a function of the encryption key and the induced voltage value;

- transmit the encrypted data to the slave terminal via the NFC transceiver circuit of the master terminal;

- obtain the voltage value induced in the NFC transceiver circuit of the slave terminal produced by the mutual approach;

- obtain, from the value received by the slave terminal and the induced voltage value, the encryption key;

- decrypt, using the encryption key, the encrypted data received by the slave terminal, obtaining the original data.

All applications that are transaction-based need a security system that allows them to perform operations safely. Possible applications include: making payments by simply bringing the phone closer to one of the many NFC terminals without contacts that are already in operation, obtaining information, discounts and offers from the so-called smart "posters" that have an NFC tag, storing information personnel that allow secure access to buildings, take a picture and transmit it wirelessly to any television or printer without any configuration, share business cards with other NFC phones.

The system object of the present invention takes advantage of the fact that communication takes place at close range. When approaching, the terminals create a magnetic field, with an appropriate device that can measure an induced value that will be variable and only known by the two terminals in the approach process.

This value will serve as the basis for encrypting the data exchanged between the two terminals. Since only the two devices involved in communication can have that value, it is very difficult for another person to have the same value. and therefore decrypt the data.

The devices involved in data exchange are usually small-sized devices with limited computing capacity. This process is simple and avoids elaboration of complex encryption and decryption systems, so it does not require much computing capacity. In addition it is not possible to alter the data transmitted by a spy since that alteration destroys the indecipherable source code and the terminals in communication detect it and give the transmission as erroneous.

It has the technical advantage that both devices are capable of having other extra parameters for their authentication _* These parameters provided by the hardware design included in both simple and inexpensive, are only shared between them, not known a priori and eliminated in the moment in which the communication ceases, which provides a high degree of security.

The great advantage of this system is its simplicity and robustness since this process is extremely simple and avoids elaboration of complex encryption and decryption systems, in addition, it avoids another vulnerability factor such as the possibility of altering the data transmitted from a spy. The latter is not possible, because such alteration destroys the indecipherable source code and the terminals in communication detect it and give the transmission as erroneous. In others, the advantages of the system are:

• Versatility and easy implantation in devices that do not integrate it from the factory {it can be a complement for the devices that do not have it, for example through a connector this device can be connected to the terminals).

• Feasibility of implementation due to the simplicity of hardware.

• Very good ratio between costs / benefits.

• Very current, booming and innovative technology.

• Optimal complement for the implementation of NFC transactions in the market, providing a strong boost in what trust and security is concerned.

BRIEF DESCRIPTION OF THE FIGURES

A series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention which is presented as a non-limiting example thereof is described very briefly below.

Figure 1 represents the proposed security system.

Figure 2 shows an operation diagram of the encryption algorithm. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows the proposed security system. The system consists of an NFC 3 mobile device (for example, any smart-phone equipped with NFC technology) and an NFC 1 terminal (which can be any terminal or device equipped with NFC technology), both incorporating a transceiver circuit Identical NFC 2, capable of generating and detecting identical field values with adequate tolerance. The NFC 2 transceiver circuit consists of an electromagnetic field generator (for example, an electromagnet 4) and an electromagnetic field detector (for example, a coil or resonant circuit 5 and a galvanometer 6), in addition to the necessary electronics (microcontroller and other electronic components) to govern the device.

The invention is based on implementing a circuit (hardware design) and including it in each device with NFC technology (the NFC 2 transceiver circuit contains the necessary circuitry; this circuit can be integrated in the mobile or can be external, connected for example via a connector ), so that a much more reliable and secure communication is allowed when it is required. In this design, special attention is paid to the arrangement of the components, since it is spice! interest its placement for the generation and detection of fields in the different devices as similar as possible, with a relative error between them minimum, practically null.

A magnetic field generator is included in the design of each device, NFC 3 mobile device and NFC 1 terminal. With this it is possible to generate a magnetic flux in the emitting device and, in the receiving device, variable induced currents according to the position of both devices, their distance, approach speed and orientation. This is why, with the corresponding field detectors, the parameters mentioned above are obtained, of equal magnitude in both elements and totally unknown before communicating, since they are only known at the time of pairing. In addition, despite the screening that is carried out to avoid other undesirable electromagnetic field sources, before establishing communication between both devices, it would be further adjusted by eliminating the offset due to external fields such as those present in the near environment or the magnetic field. In this way, another limitation is added to a possible listening remotely, since the two communication devices would correct a different offset than the one attempted to correct in another position. Figure 2 shows an operation diagram of the communication between two terminals, master terminal 7 and slave terminal 8, and the encryption algorithm thereof. The master 7 and slave 8 terminals can change their roles during communication; that is, initially the master terminal may be the NFC 3 mobile device and this will then become the slave terminal, or vice versa. It can be considered, for example, that the master terminal 7 that initiates the communication is the mobile device NFC 3 and that the slave terminal 8 is the NFC terminal 1, but could be considered the other way around.

Initially there is a mutual approach between the master terminal 7 and the slave terminal 8, for example the user brings his NFC 3 mobile device to the NFC 1 terminal. Either one, NFC 3 mobile device or NFC 1 terminal, can be a active NFC system, or even both. This approach produces an electromagnetic induction 101 that allows the creation of a random IV induced voltage value in the NFC 2 transceiver circuits, known only to the two terminals, master 7 and slave 8.

After obtaining 100 the value of the induced voltage IV (known only by the two terminals, the NFC 3 mobile device and the NFC 1 terminal), the data is encrypted following an algorithm represented in Figure 2. The slave terminal 8 also obtains (109) the value of induced voltage IV.

The master terminal 7 obtains 102 an MK encryption key stored in a memory. With this MK encryption key 105 the original DATA data is encrypted, obtaining the DT encrypted data to be transmitted. In order for the slave terminal 8 to have the same key and to be able to decrypt the data, the master terminal 7 obtains 103 and transmits 104 a Cft value containing the key and in which the induced voltage value IV is also entered, known only by The two terminals. For example, the Cft value can be considered as the sum of the encryption key MK and the induced voltage value IV (Cft = MK + IV), or the subtraction or any other operation. In essence, Cft = (MK.IV), the function f being known by both terminals. Since the key encryption values MK and induced voltage value IV are numbers, arithmetic or binary operations can be applied (in the case of Figure 2 a simple operation has been chosen - the sum - but the XOR operation can be chosen , for example). After transmitting 104 the Cft value, 106 the data encrypted with the encryption key MK (encrypted data DT) is transmitted. Thus, the receiver (slave terminal 8) has for S

on the one hand the Cft value and on the other hand it has the DT encrypted data. The first thing that slave terminal 8 does is to obtain 107 the MK encryption key. For this, since the receiver has the same induced voltage value IV as the transmitter, and knows the function f that relates the encryption key MK and the Cft value, it obtains 107 the encryption key MK easily (for example, if Cft = MK + IV, subtracting the induced voltage value IV from the received Cft value). After obtaining the encryption key MK 107 the slave terminal 8 proceeds to decrypt 108 the encrypted data DT applying the reverse operation to which it was applied in the encryption, thereby obtaining the original DATA data.

Claims

1. Security system for NFC communications, comprising an NFC terminal (1) and an NFC mobile device (3), any one of them acting in an NFC communication as a master terminal (7) and the other as a slave terminal (8) , characterized in that both the NFC terminal (1) and the device. NFC mobile (3) have a substantially identical NFC transceiver circuit (2);

Why the master terminal (7) is configured to:

- before the electromagnetic induction (101) produced by a mutual approach, obtain (100) the value of induced voltage (IV) in its NFC transceiver circuit (2);

- encrypt (105) the original data (DATA) with an encryption key (MK), obtaining encrypted data (DT);

- transmit (104) to the slave terminal (8), using the NFC transceiver circuit (2), a value (Cft) that is a function (f) of the encryption key (MK) and the induced voltage value (! V) ;

- transmit (106) to the slave terminal (8), via the NFC transceiver circuit (2), the encrypted data (DT);

and why the slave terminal (8) is configured to:

- obtain (109) the induced voltage value (IV) in its NFC transceiver circuit (2) produced by the mutual approach;

- obtain (107), from the value (Cft) received and the induced voltage value (IV), the encryption key (MK);

- decrypt (108), using the encryption key (MK), the encrypted data (DT) received, obtaining the original data (DATA).

2. System according to claim 1, characterized in that each NFC transceiver circuit (2) comprises data processing means, a magnetic field generator (4) and a magnetic field detector (5,6).

3. System according to any of the preceding claims, characterized in that the NFC transceiver circuit (2) is integrated in the corresponding terminal (1, 3).

System according to any of the preceding claims, characterized in that the NFC transceiver circuit (2) is external to the corresponding terminal (1, 3), being connected to it by means of a connector.

5. Security method for NFC communications between an NFC terminal (1) and an NFC mobile device (3) that have a substantially identical NFC transceiver circuit (2), any one of them acting on an NFC communication as a master terminal (7 ) and the other as a slave terminal (8), characterized in that it comprises:

- before the electromagnetic induction (101) produced by a mutual approach, obtain (100) the induced voltage value (IV) in the NFC transceiver circuit (2) of the master terminal (7);

- encrypt (105) with an encryption key (MK) the original data (DATA) to be transmitted by the master terminal (7), obtaining encrypted data (DT);

- transmit (04) to the slave terminal (8), via the NFC transceiver circuit (2) of the master terminal (7), a value (Cft) that is a function (f) of the encryption key (MK) and the value of induced voltage (IV);

- transmit (106) to the slave terminal (8), via the NFC transceiver circuit (2) of the master terminal (7), the encrypted data (DT);

- obtain (109) the induced voltage value (IV) in the NFC transceiver circuit (2) of the terminator! slave (8) produced by mutual approach;

- obtain (07), from the value (Cft) received by the slave terminal (8) and the induced voltage value (IV), the encryption key (MK);

- decrypt (108), using the encryption key (MK), the encrypted data (DT) received by the slave terminal (8), obtaining the original data (DATA).