Method and system for secure communication in near field communication network

SYSTEM AND METHODS FOR SECURE COMMUNICATION IN NEAR FIELD COMMUNICATION NETWORK IN NEAR FIELD COMMUNICATION NETWORK

<p>BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to communication in a short-range wireless communication network, and more particularly to secure communication in close-range communication.</p>

<p>Currently, wireless communication devices such as portable telephones, personal digital assistants, smart tags, audio/video devices, and set-top boxes are frequently used for communication. The communication devices may communicate with each other through short-range wireless communication. For example, a mobile phone is a set-top box (hereinafter referred to as 'NFC') through short-range wireless communication, for example, short-range radio (Bluetooth), infrared (Infrared light: IR) and near field communication (hereinafter referred to as 'NFC'). set-top box).</p><p>Near Field Communication (NFC) is called a contactless-type near field communication technology. NFC uses a frequency band of 13.56 MHz and transmits data at a data rate of up to 424 Kbps. In NFC, communication devices operate in close proximity, for example within about 10 centimeters, and consume very low power. As a result, near field communication (NFC) is becoming more prevalent for exchanging and sharing information in NFC compatible communication devices.</p><p>NFC-compatible communication devices adhere to the International Organization for Standardization (ISO) 18092 standard. In Near Field Communication (NFC), the NFC-compatible communication devices may communicate with each other in an active mode and/or a passive mode. In the active mode, the NFC-compatible communication device, for example the first device, has its own power source and may generate a Radio Frequency (Radio Frequency) wavelength for transmission of a data frame. In the passive mode, the first device does not have its own power source. Therefore, communication regarding the first device is always initiated by another NFC-compatible communication device known as the initiating device.</p><p>In NFC, the target device cannot initiate commands by itself, regardless of whether the communication is in an active mode or a passive mode. In the passive mode, the initiating device first sends a request message to perform communication with the first device (generally referred to as a target device). This generates an RF wavelength between the initiating device and the target device. The RF wavelength drives a receiving device in the target device. The target device responds in a load modulation manner.</p><p>In general, communication using NFC technology is inherently secure because it takes place between communication devices over very short distances, for example up to 10 centimeters. However, since the communication is through a wireless medium, a security framework must be provided in order to protect confidentiality, data integrity and reliability. Several standards are being developed to provide a security framework for NFC communication. The security framework is supported in the NFC-SEC (Near Field Communication-SECurity, hereinafter referred to as 'NFC-SEC') layer. Since the NFC-SEC layer provides security services to an application layer and a Media Access Control (hereinafter referred to as 'MAC') layer, privacy and security functions are provided in a communication device.</p><p>The two basic services performed by the NFC-SEC layer are secure channel service and shared secret service. The secure channel service uses a link key to establish a secure channel. Thereafter, a link encryption key and a link integrity key are derived from the link key. Therefore, all data frames received from various applications use the same link key during communication.</p><p>In the shared secret service, a shared secret is authorized between a plurality of devices. A key is chosen or generated based on a shared secret. This shared secret and the key are associated with applications residing on a plurality of communication devices. Therefore, the data frame transmission associated with the application is made based on the shared key. In the shared secret service, each application may use a different key for transmission of data frames.</p><p>For every data frame transmission, the NFC device maintains and increments a sequence number (hereinafter referred to as 'SN') counter. Next, the NFC-SEC layer inserts the value of the SN into the SN field of request commands and response commands exchanged between devices in communication. The SN field is a 3-byte (24-bit) field in the request and response commands. The application service and/or secure channel service used by the NFC link may have the maximum limit of a frame, e.g. 2 to the power of 24 (2<sp>24</sp>) frames, use the same key for request and response commands. Before inserting a new value into the SN field, the NFC device compares the counter with the maximum limit value. Then, when the value of the SN reaches the maximum limit value, the SN counter is cycled and reset. The data communication of the NFC link is terminated and a new set of keys is determined for the next communication.</p><p>However, in the case of the prior art, since the same key is used for exchanging a large number of data frames, there is a possibility of a brute force attack. Also, when the SN counter is reset, the NFC-SEC layer pauses the NFC communication and stops exchanging data frames. Therefore, this results in a sudden discontinuity in NFC communication. Before the NFC-SEC re-instantiates a new set of keys and starts with an initial value of a new SN, higher layer connections may also experience discontinuities in the NFC link.</p><p>Therefore, there is a need for establishing secure and continuous communication between communication devices in NFC.</p>

<solutionproblem><p>The present invention proposes a method and system for protecting against brute force attacks and repeated attacks by dynamically changing keys used for encryption and decryption. </p><p>And the present invention provides a method and system for avoiding abrupt interruption of service that occurs when the NFC-SEC layer sets a new key and/or a new value for the sequence number (SN) field by dynamically changing the keys during NFC communication. suggest </p></solutionproblem><meansproblemsolution><p>The method proposed in the present invention is; In a method for secure communication between a plurality of electronic devices in a near field communication (NFC) network, a first electronic device shares a plurality of keys with at least one of the plurality of electronic devices, and a first key among the plurality of keys , exchanging data based on the at least one of the plurality of electronic devices and the first key, and exchanging the first key with the plurality of the plurality of electronic devices while exchanging the data after satisfying at least one predetermined criterion It is characterized by exchanging at least one of the keys.</p><p>The system proposed in the present invention is; In a system for secure communication between a plurality of electronic devices in a near field communication (NFC) network, the system includes a first electronic device, wherein the first electronic device stores a plurality of keys with at least one of a plurality of electronic devices; a transceiver for sharing and exchanging data with at least one of the plurality of electronic devices based on a first key, selecting the first key from among the plurality of keys, and satisfying at least one predetermined criterion and a processor for exchanging the first key with at least one of the plurality of keys while exchanging the data.</p></meansproblemsolution><effectiveness><p>The present invention can protect from brute force attacks and repeated attacks by dynamically changing keys used for encryption and decryption. </p><p>And by dynamically changing keys during NFC communication, the present invention can prevent an abrupt interruption of a service that occurs when the NFC-SEC layer sets a new key and/or a new value for the sequence number field (SN).</p></effectiveness>

<p>Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only the parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to obscure the gist of the present invention.</p><p>1 depicts an exemplary environment 100 in which various embodiments of the present invention may be practiced. The environment 100 includes a plurality of electronic devices, for example, the electronic device 105 and the electronic device 110 . Here, only two electronic devices are shown in the environment 100, but a larger number of electronic devices may be included in the environment 100. The electronic devices 105 and 110 may be at least one of a portable telephone, a smart card, a personal portable terminal, and a computer, and may also be other devices. A plurality of electronic devices may communicate with each other through a communication network.</p><p>As an embodiment, the electronic devices 105 and 110 may communicate with each other through short-range wireless communication technology. Examples of near field communication technologies include, but are not limited to, near field radio, infrared and near field communication (NFC). As an embodiment, the electronic devices 105 and 110 may communicate with each other through near field communication (NFC). Therefore, the electronic devices 105 and 110 are NFC compatible electronic devices. For the purpose and clarity of the description, the electronic devices 105 and 110 will be referred to as NFC device 105 and NFC device 110, respectively.</p><p>A pair of NFC devices, eg, the NFC device 105 and the NFC device 110, may operate in one of operating modes, eg, a reader/writer mode, a peer-to-peer mode, and a card emulation mode. can work </p><p>In the reader/writer mode, the NFC device is capable of reading NFC forum command tag types. In this mode, the tag can be active or passive. However, when a reader NFC device is adjacent to the tag and is initialized and reads signals, the tag becomes active for communication. In the card emulation mode, the NFC device acts as an NFC tag to act as a general contactless smart card, and the other NFC device acts as a reader/writer device. In the peer-to-peer mode operation, the legacy NFC device performs the half-duplex mode operation using protocols that enable the peer-to-peer mode operation. In this mode of operation, the NFC device that initiates the communication is called the initiating device and the device with which the communication is established is called the target device.</p><p>In NFC, when a communication link is established, the NFC-SEC protocols can be used to provide a secure channel framework for data exchange. In NFC-SEC, multiple keys are authorized between multiple devices, for example the NFC device 105 and the NFC device 110 . The NFC-SEC then maintains a table of multiple keys with a reference to each key called a key-index. Thereafter, a first key is selected from a plurality of keys using NFC-SEC commands, and the first key is maintained in NFC-SEC as the first key that can be used to secure data exchange over the link.</p><p>Next, data is exchanged between the NFC devices 105 and 110 based on the first key for providing security. In one embodiment, the key facilitates encryption of data. In another embodiment, the key facilitates authentication of data. In one embodiment, in order to provide security and protect the integrity of the data frame, a message authentication code (hereinafter referred to as 'MAC') is added to each data frame exchanged between NFC devices. In one embodiment, a security standard such as the Advanced Encryption Standard is used to calculate the MAC. A sequence number (SN) is also added to each frame to provide message sequence indecision and prevent data repetition attacks. In one embodiment, the sequence number is used to identify a data manipulation attack.</p><p>After that, the first key is dynamically changed based on a first predetermined criterion. In one embodiment, the first key is dynamically exchanged for a second key. The second key is selected from a set of a plurality of keys previously approved between the NFC device 105 and the NFC device 110 . In an embodiment, the first predetermined criterion is based on the number of data frames exchanged between the NFC devices. In another embodiment, the first predetermined criterion is based on an amount of time that elapses when a communication is in progress. In another embodiment, the first predetermined criterion is based on identification of a security threat attack.</p><p>2 illustrates a first electronic device according to an embodiment of the present invention. For the description of the first electronic device, reference will be made to FIG. 1 , but it will be apparent to a person skilled in the art that this embodiment can be described with the help of other suitable embodiments of the present invention. For description, the first electronic device is referred to as the NFC device 105 .</p><p>The NFC device 105 includes a transceiver 205 and a processor 210 . The transceiver 205 may share a plurality of keys between a plurality of electronic devices, for example, the NFC device 105 and the NFC device 110 . Next, the processor 210 selects a first key from a plurality of shared keys and assembles data exchanged based on the first key. In an embodiment, the processor 210 decrypts the received data based on the first key.</p><p>Next, the transceiver 205 exchanges data between the NFC devices 105 and 110 based on the first key. In an embodiment, the transceiver 205 is capable of exchanging data based on functions and commands supported by the NFC standard. In another embodiment, the transceiver 205 uses a plurality of Parameter Exchange (hereinafter referred to as 'PAX') protocol data units (hereinafter referred to as 'PDU') to obtain data based on an approved security key. It is possible to exchange The processor 210 is also capable of dynamically initiating authorization for the key that can be used by the application and/or link layer. In an embodiment, the processor 210 changes the first key based on a predetermined criterion.</p><p>In another embodiment, the processor 210 dynamically exchanges the first key with a second key while the communication is in progress. Therefore, the processor 210 dynamically changes the first key to the second key without pausing and/or stopping communication between the NFC device 105 and the NFC device 110 . In an embodiment, the processor 210 selects the second key from a plurality of keys shared between the NFC devices 105 and 110 . The processor 210 may also add a sequence number (SN) to each frame to provide message sequence integrity and prevent data repetition attacks. The processor 210 also maintains a counter for the SN.</p><p>3 illustrates a frame format in which the data is exchanged according to an embodiment of the present invention. In one embodiment, the frame format used by the NFC-SEC protocol is an NFC-SEC Protocol Data Unit. The frame NFC-SEC is used to transmit Near Field Communication Interface and Protocol-1 (NFCIP-1) Data Exchange Protocol in a secure manner. In an embodiment, the data format corresponds to the NFCIP-1 security services and a protocol developed by the European Computer Manufacturers Association (ECMA) standard body. The frame format has a plurality of fields carrying various types of information. For example, the frame format is shown to include a Secure Exchange Protocol (SEP) field, an NFC-SEC-01 field, an SN field, a DataLen field, an EncData field, and a MAC field. Although the frame format shown in Fig. 3 includes six fields, it does not limit the scope of the invention, and the frame format may have more or fewer fields.</p><p>Field 305 is a Secure Exchange Protocol (SEP) field. The SEP field is used to identify an exchange protocol used during communication. Field 310 is an NFC-SEC-01 field. The NFC-SEC-01 field includes a one-byte "Packet IDentifier (hereinafter referred to as 'PID')" field that identifies a ciphertext criterion used to provide security. The field 315 is a sequence number (SN) field. The SN field indicates a sequence number of an NFC-SEC PDU. The field 320 is a data length (DataLen) field. The DataLen field is used to indicate a byte of encoded data to be sent within the data frame. The field 325 includes an encrypted data (EncData) field. The EncData field provides a detailed description of the encrypted data. The field 330 is for a message authentication code (MAC). The MAC field is used to verify authentication and message integrity. </p><p>4 is a flowchart illustrating a method 400 for establishing secure communication in near field communication (NFC) according to an embodiment of the present invention. To describe the method 400, reference will be made to FIGS. 1 and 2 . However, it will be apparent to a person skilled in the art that this embodiment may be described with the aid of other suitable embodiments of the present invention. The method 400 may also include more or less steps as depicted in FIG. 4 . In addition, the order of the above processes may also vary.</p><p>405 In the process, the method 400 is disclosed. A first electronic device, for example the NFC device 105, sends an instruction to another electronic device, for example the NFC device 110, to establish a communication link. In an embodiment, when the first electronic device comes within a predetermined distance from the other electronic device, the instruction is automatically sent to the other electronic device. For example, if the NFC device 105 is adjacent to the NFC device 110, for example within a distance of 10 centimeters, an indication is sent to the NFC device 110 .</p><p>Once the initial communication link is established, the NFC device is activated to exchange data. In step 410 , a plurality of keys are first exchanged between the NFC device 105 and the NFC device 110 . In step 415, a first key is selected from the plurality of keys for exchanging data. The plurality of keys are arranged in the order of the plurality of devices corresponding to the plurality of key-indexes. For example, the first key may be a predefined key-index, for example, an index '1' in each of the plurality of NFC devices communicating with each other. Thereafter, in step 420 , the data is exchanged between the NFC device 105 and the NFC device 110 based on the first key.</p><p>In an embodiment, the transceiver 205 exchanges data based on the first key. Thereafter, the NFC device 105 determines to change the first key to a second key based on a predetermined criterion. In one embodiment, the key-index is shared between a plurality of NFC devices. In step 425, while exchanging data, the first key is dynamically exchanged with at least one of the plurality of keys, for example, the second key. The NFC device may exchange the data based on one key corresponding to the shared key-index. In one embodiment, the NFC-SEC layer in an NFC device ensures that all the frames are sent into the transmit queue before changing the key. Thereafter, the method 400 ends in step 430 .</p><p>In one embodiment, a plurality of NFC commands and functions are exchanged in different layers within the NFC device to dynamically change a key. In addition, a plurality of NFC commands and functions are also exchanged between the plurality of NFC devices while communicating with each other. Therefore, the method is also described by two implementation methods which will be described later. The following implementation methods are described in relation to a plurality of functions and instructions. The functions and instructions used in the following implementation methods are for clarity only and do not limit the scope of the invention. Therefore, a person skilled in the art may use other functions or instructions to implement the method.</p><p>In a first implementation method, an NFC-SEC layer within an NFC device, eg, the NFC device 105, generates a short-range decision to change a key for the first time. For example, the NFC-SEC device 105 determines to change the first key to a second key. In one embodiment, the second key corresponds to a key-index shared during communication. Therefore, the NFC-SEC layer in the NFC device 105 sends a CHANGE_KEY_REQ [key-index] command to the Logical Link Control Protocol (hereinafter referred to as 'LLCP') layer in the NFC device. Here, CHANGE_KEY_REQ [key-index] refers to the CHANGE_KEY_REQ command including key-index. In one embodiment, the key-index is a unique identifier for the second key stored in a table in the NFC device. In one embodiment, communication in the LLCP layer is a peer-to-peer communication mode for NFC devices defined by the NFC Forum. The NFC-SEC layer ensures that all data frames in the transmit queue are transmitted before initiating the CHANGE_KEY_REQ. In one embodiment, the LLCP in the NFC device 105 transitions the state of the LLCP from the ACTIVE state to the CONFIGURE state upon receiving this command. Therefore, the transmission of additional data frames to be transmitted from the LLCP connection to the NFC-SEC is stopped.</p><p>A change key request can be initiated between NFC devices via a CHANGE_KEY_REQ command and a response is received via a CHANGE_KEY_RSP command. Then, the LLCP layer of the NFC device 105 sends a parameter exchange (PAX) request command having the key-index corresponding to the second key to another NFC device, for example, the NFC device 110 . Then, the NFC device waits for a PAX response from the NFC device 110 . In one embodiment, the PAX request command is secured using the first key.</p><p>In an embodiment, all data frames are exchanged based on the first key until the NFC device 105 receives a success command from the NFC device 110 . After receiving the PAX[key-index] from the NFC device 105, the LLCP layer in the NFC device 110 sends a CHANGE_KEY_REQ[key-index] event to the NFC-SEC layer in the NFC device 110 . Here, PAX[key-index] refers to a PAX command including a key-index. In an embodiment, the LLCP layer in the NFC device 110 transitions from ACTIVE to CONFIGURE state. In one embodiment, the NFC-SEC layer will use the first key to complete the transmission of the frames held in the transmission queue.</p><p>Furthermore, if the key index given by the NFC device 105 is known and valid in the NFC-SEC layer of the NFC device 110, then the NFC-SEC layer sets the CHANGE_KEY_RSP[key-index] of the NFC device 110 . sent to the LLCP. Here, CHANGE_KEY_RSP[key-index] refers to the CHANGE_KEY_RSP command including the key index. For a subsequent successful key change, the LLCP layer of the NFC device 110 may send a PAX[key-index] response to the NFC device 105 . Therefore, a new transmission will be made based on the key corresponding to the shared key-index. In one embodiment, the LLCP link transitions from the CONFIGURE state to the ACTIVE state.</p><p>In one embodiment, the PAX command will be based on the first key. If the NFC-SEC layer of the NFC device 110 does not approve the change of the key, a CHANGE_KEY_RSP [fail code] command is sent to the LLCP. Here, CHANGE_KEY_RSP [failure code] refers to the CHANGE_KEY_RSP command including the failure code. After that, the PAX with the failure code is sent to the NFC device 105 . Therefore, the first key is not changed. The LLCP link will then transition from the CONFIGURE state to the ACTIVE state and communication will continue based on the first key.</p><p>In the second implementation method, dynamic key change may also be handled by instructions in the NFC-SEC layer. This method can be used independently in the LLCP layer. After transmission of the random count of the data frame, the NFC-SEC layer may decide to change the security key used in the secure channel framework. In the above implementation method, it is assumed that a set of keys has already been approved and verified between the two NFC devices and that the values are stored in a key table referenced by a key-index.</p><p>To change the key via this method, the NFC-SEC layer of the NFC device 105 generates a short-range decision to change the first key to a second key corresponding to a key-index. In one embodiment, the NFC-SEC layer transmits all frames in the transmit queue and ensures that all frames in the receive queue are delivered to a higher layer. Thereafter, after selecting the second key corresponding to the key-index, the NFC-SEC layer changes the communication state from Confirmed to Verify state. If another device can also use the same key-index, the NFC-SEC layer of the NFC device 105 verifies a data exchange protocol request frame DEP-REQ (VFY-REQ) command, It is sent to the NFC device 110 together with the key-index, which is a parameter for operation. In one embodiment, detailed description of the data exchange protocol and frame formats for DEP_REQ and DEP_RES are used according to the Near Field Communication Interface and Protocol (NFCIP-1) ECMA 340 standard. </p><p>Upon receipt of a successful data exchange protocol response frame DEP_RES (VFY_RES), the NFC-SEC layer transitions from the Verify state to the Confirmed state. However, if DEP_RES [error] is received, NFC-SEC returns to the IDLE state. Here, DEP_RES[error] refers to a DEP_RES command including an error. In an embodiment, until the order of DEP_REQ (VFY_REQ) and DEP_RES (VFY_RES) is completed, frames received from an upper or lower layer are decoded and buffered or dropped.</p><p>In the NFC device 110 , the NFC-SEC layer checks the key-index upon receiving the DEP_REQ (VFY_REQ) from the NFC device 105 . If the key-index is valid, a DEP_RES (VFY_RES) frame is sent and the state of NFC-SEC maintains the Confirmed state. Therefore, the key used in the NFC-SEC layer is changed to the second key referred to by the key-index. Upon receipt of DEP_REQ (VFY_REQ), the response is sent as the next frame from the NFC-SEC layer. No other frames are transmitted during this sequence. However, if the key-index is not valid, a DEP_RES[ERROR] command is sent to the initiator, and NFC-SEC returns to the IDLE state.</p><p>5 is a message flow diagram illustrating a method for establishing secure communication in near field communication (NFC) according to an embodiment of the present invention. A plurality of applications are registered in a plurality of electronic devices, for example, the electronic device 105 and the electronic device 110 . To clearly describe the invention, the electronic device 105 and the electronic device 110 are also referred to as an initiating LLCP and a target LLCP, respectively.</p><p>First, an NFC device, for example, an NFC-SEC layer in the NFC device 105, decides to change the first key to a second key. In one embodiment, the second key corresponds to a key-index shared during a previous communication. In step 505, the NFC-SEC layer in the NFC device 105 sends a CHANGE_KEY_REQ [key-index] command to the LLCP layer. In an embodiment, the key-index is a unique identifier for the second key stored in a table of a plurality of NFC devices communicating with each other.</p><p>The NFC-SEC layer ensures that all data frames in the transmit queue are transmitted before initiating CHANGE_KEY_REQ. In one embodiment, the LLCP in the NFC device 105 changes the state of the LLCP link from ACTIVE to CONFIGURE state upon receiving the command. Therefore, the transmission of additional frames to be sent from the LLCP connection to the NFC-SEC is stopped. The change key request may be initiated between the NFC devices via a CHANGE_KEY_REQ command and a response is received via a CHANGE_KEY_RSP command.</p><p>510 In the process, the LLCP layer of the NFC device 105 sends a PAX request command, for example, PAX [key-index], together with the key-index corresponding to the second key to another NFC device, for example, the NFC device 110 send to And the NFC device waits for a PAX response from the NFC device 110 . In one embodiment, the PAX request command is secured using the first key. In an embodiment, until the NFC device 105 receives a success command from the NFC device 110, all data frames are exchanged based on the first key.</p><p>515 In the process, the LLCP layer in the NFC device 110 sends a CHANGE_KEY_REQ [key-index] event to the NFC-SEC layer after receiving the PAX [key-index] from the NFC device 105 . In an embodiment, the LLCP layer in the NFC device 110 transitions from ACTIVE to CONFIGURE state after receiving the CHANGE_KEY_REQ [key-index]. In an embodiment, the NFC SEC layer may complete transmission of frames existing in the transmission queue using the first key.</p><p>520 In the process, if the key-index given by the NFC device 105 is known and valid in the NFC-SEC layer of the NFC device 110, then the NFC-SEC layer is CHANGE_KEY_RSP[key- index]. In step 525 , the LLCP layer of the NFC device 110 will send a PAX [key-index] to the NFC device 105 . In step 530, the CHANGE_KEY_RSP [key-index] is sent from the LLCP of the NFC device 105 to the NFC-SEC layer.</p><p>Therefore, a new transmission is made based on the key corresponding to the approved and shared new key-index. In one embodiment, the LLCP link transitions from the CONFIGURE state to the ACTIVE state. In one embodiment, the PAX command is based on the first key. If the NFC-SEC layer in the NFC device 110 does not approve the change to the key, a CHANGE_KEY_RSP [fail code] command is sent to the LLCP. Then, the PAX with the failure code is sent to the NFC device 105 . Therefore, the first key is not changed, and the LLCP link transitions from the CONFIGURE state to the ACTIVE state.</p><p>The various embodiments of the present invention described above provide the following advantages. The present invention provides a method for secure communication in an NFC communication network. The method provides protection from brute force and repeat attacks by dynamically changing the keys used for encryption and decryption. When the NFC-SEC layer sets a new key and/or a new value for the sequence number field (SN), the method also prevents abrupt interruption of service. Moreover, since the current commands within LLCP and NFC-SEC are used to establish communication with a new key for all communicating devices, the method reduces additional processing during communication. Even when there is a higher layer above the NFC-SEC layer, the above method can be used to change the key.</p><p>On the other hand, although specific embodiments have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.</p>