JP5741677B2 - Communication apparatus and communication method - Google Patents

Description

  The present invention relates to a communication device that transmits and receives stream data, and more particularly to a technique for communicating stream data and information used for encrypted communication of the stream data.

  Non-stream data such as key data used for encryption of stream data is transmitted between communication terminals that transmit and receive stream data such as audio data and video data by RTP (Real-time Transport Protocol), for example, RTCP (Real-time Transport Control). In some cases, data is transmitted and received in parallel with stream data using a protocol other than RTP, such as Protocol. In this case, since a packet other than RTP is used for transmission / reception of non-stream data, the network load becomes excessive.

  On the other hand, in Patent Document 1, non-stream data is added to an RTP packet as an RTP extension header, and stream data and non-stream data are simultaneously transmitted and received between communication terminals without increasing the network load. Technology is disclosed.

JP 2008-306623 A

  However, when a gateway intervenes between communication terminals and the RTP layer is terminated at this gateway, the extension header added to the RTP packet by one communication terminal is discarded by this gateway, and the other communication There may be a situation where it does not reach the terminal.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to increase the network load between communication apparatuses even in a network environment in which a gateway that terminates a transmission protocol layer of stream data is interposed. An object of the present invention is to provide a technique capable of transmitting and receiving stream data and information used for encrypted communication of the stream data.

  In order to solve the above-described problem, the present invention provides stream data stored in a predetermined packet among packets sequentially transmitted to a partner device, including information related to encrypted communication including key data used for encrypted communication of stream data. By replacing, the data is transmitted to the partner device, and is extracted from a predetermined packet among the packets sequentially received from the partner device, and is received from the partner device.

For example, the communication device of the present invention is a communication device that performs encrypted communication of stream data including audio data or video data with a partner device,
Transmission means for sequentially transmitting packets including the stream data to the counterpart device;
Replacement means for replacing the stream data stored in any of the packets sequentially transmitted by the transmission means with information relating to cryptographic communication;
Receiving means for sequentially receiving packets including the stream data sequentially transmitted from the counterpart device;
Extraction means for extracting information related to the encrypted communication from any of the packets sequentially received by the receiving means;
Key exchange means for exchanging key data used for encrypted communication with the counterpart device;
Cryptographic communication means for performing cryptographic communication of the stream data with the counterpart device using the key data exchanged by the key exchange means,
The key exchange means is
When starting the encrypted communication, information for notifying that the key exchange is started is stored in the predetermined packet transmitted by the transmitting unit as the information related to the encrypted communication in the replacing unit. If the public key of the counterpart device is extracted as the information related to the encryption communication by the extraction means, the public key of the communication device is used as the information related to the encryption communication. And replacing the stream data stored in the predetermined packet transmitted by the transmitting means, encrypting the common key of the own communication device using the public key of the counterpart device, and encrypting the own communication device The common key is replaced with the stream data stored in the predetermined packet transmitted by the transmitting unit, as information related to the encrypted communication, in the replacing unit Then,
When the information for notifying that the key exchange is started is extracted as the information related to the encrypted communication by the extracting means, the public key of the communication apparatus is used as the information related to the encrypted communication, and the replacing means If the public key of the counterpart device is extracted as information related to the encrypted communication by the extraction means by replacing the stream data stored in the predetermined packet transmitted by the transmission means, the own communication apparatus Is encrypted using the public key of the counterpart device, and the encrypted common key of the communication device is transmitted to the replacement unit as the information related to the encrypted communication. Replacing the stream data stored in the packet of
When the common key of the counterpart device encrypted as information related to the encrypted communication is extracted by the extraction means, the encrypted common key of the counterpart device is decrypted using the private key of the local communication device And
The encryption communication means includes
Encryption of the stream data stored in packets sequentially transmitted by the transmission means, using the common key of the own communication device exchanged with the counterpart device by the key exchange means and the common key of the counterpart device; and The stream data stored in the packets sequentially received by the receiving means is decoded.

The communication method of the present invention is a communication method for performing encrypted communication of stream data including audio data or video data between a first communication device and a second communication device,
The first communication device is:
Replacing the stream data stored in a predetermined packet to be transmitted to the second communication device with information for notifying the start of key exchange;
Extracting the public key of the second communication device from the predetermined packet received from the second communication device;
Replacing the stream data stored in a predetermined packet to be transmitted to the second communication device with the public key of the own communication device;
The common key of the local communication device is encrypted using the public key of the second communication device, and the stream data stored in a predetermined packet to be transmitted to the second communication device is converted into the encrypted local key. Replace with the common key of the communication device,
Extracting the encrypted common key of the second communication device from the predetermined packet received from the second communication device, and using the encrypted common key of the second communication device as the secret of the own communication device Decrypt with the key,
From the encryption of the stream data stored in the packet sequentially transmitted to the second communication device using the common key of the own communication device and the common key of the second communication device, and the second communication device Decoding the stream data stored in the sequentially received packets;
The second communication device is
Extracting information for notifying that the key exchange starts from a predetermined packet received from the first communication device;
Replacing the stream data stored in a predetermined packet to be transmitted to the first communication device with the public key of the own communication device;
Extracting the public key of the first communication device from the predetermined packet received from the first communication device;
The common key of the own communication device is encrypted using the public key of the first communication device, and the stream data stored in a predetermined packet to be transmitted to the first communication device is converted into the encrypted own key. Replace with the common key of the communication device,
Extracting the encrypted common key of the first communication device from the predetermined packet received from the first communication device, and using the encrypted common key of the first communication device as a secret of the own communication device Decrypt with the key,
From the first communication device, the encryption of the stream data stored in the packet sequentially transmitted to the first communication device using the common key of the own communication device and the common key of the first communication device The stream data stored in the sequentially received packets is decoded.

  According to the present invention, even in a network environment in which a gateway that terminates a stream data transmission protocol layer is interposed, stream data and information used for encrypted communication of the stream data are transmitted between communication terminals without increasing the network load. You can send and receive.

FIG. 1 is a schematic diagram of an IP telephone terminal 1 according to the first embodiment of the present invention. FIG. 2A is a diagram schematically illustrating an example of the key data 301, and FIG. 2B is a diagram schematically illustrating an example of the call data 305 in which the extension bit portion is replaced with the key data. is there. FIGS. 3A and 3B are diagrams for explaining an example of a method of superimposing a preamble signal on transmission call data. FIG. 4 is a flowchart for explaining the key exchange process of the IP telephone terminal 1 according to the first embodiment of the present invention. FIG. 5 is a flowchart for explaining the key exchange process of IP telephone terminal 1 according to the first embodiment of the present invention. FIG. 6 is a sequence diagram for explaining the key exchange operation between the IP telephone terminals 1 according to the first embodiment of the present invention connected via the gateway 2 that terminates the RTP layer. FIG. 7 is a schematic diagram of an IP telephone terminal 1a according to the second embodiment of the present invention. FIG. 8 is a sequence diagram for explaining the key exchange operation between the IP telephone terminals 1a according to the second embodiment of the present invention connected via the gateway 2 that terminates the RTP layer.

  Embodiments of the present invention will be described below.

<First embodiment>
FIG. 1 is a schematic diagram of an IP telephone terminal 1 according to the first embodiment of the present invention.

  As shown in the figure, the IP telephone terminal 1 of the present embodiment includes a communication IF unit 101, a man-machine IF unit 102, a SIP processing unit 103, an RTP processing unit 104, a telephone function unit 105, and a voice CODEC 106. , Key data replacement unit 107, preamble superposition unit 108, encryption processing unit 109, decryption processing unit 110, key data extraction unit 111, preamble detection unit 112, audio data interpolation unit 113, and key exchange processing unit 114.

  The communication IF unit 101 is an interface for communicating with a partner terminal, and includes communication protocols (TCP (Transmission Control Protocol), UDP (User Datagram Protocol), IP (Internet Protocol), Ethernet ( Registered trademark), etc.).

  The man-machine IF unit 102 is an interface for a user to perform telephone calls and various operations. Although not shown, an operation unit such as a handset, a speaker, a hook button, and a dial key, and a display unit such as an LCD and an LED are provided. Prepare.

  The SIP processing unit 103 establishes / releases a SIP session by exchanging SIP messages with a partner terminal via a SIP server (not shown) in accordance with SIP (Session Initiation Protocol).

  The RTP processing unit 104 transmits / receives call data to / from the counterpart terminal via the SIP session established by the SIP processing unit 103 in accordance with RTP.

  The voice CODEC 106 is a G.264 standard developed by ITU-T. This codec performs encoding and decoding of an audio signal in accordance with H.711. Specifically, an analog audio signal input from the man-machine IF unit 102 is converted into 8-bit PCM (Pulse Code Modulation) data, and each data length (PCM data string) stored in the payload of the RTP packet Are sequentially output as call data for transmission. In addition, the incoming call data that is sequentially input is converted into an analog voice signal and output from the man-machine IF unit 102.

  Of the transmission call data sequentially output from the voice CODEC 106, the key data replacement unit 107 converts the transmission call data designated by the key exchange processing unit 114 into, for example, the key data as shown in FIG. It replaces with key data 301 including a key data identifier 302 indicating a type (public key or common key) and an attribute (RSA method or DES method) and a key data body 303, and is added to the preamble superimposing unit 108. hand over. The transmission call data other than the transmission call data designated by the key exchange processing unit 114 is passed to the preamble superimposing unit 108 as it is.

  The preamble superimposing unit 108 superimposes the preamble signal on the transmission call data designated by the key exchange processing unit 114 among the data sequentially output from the key data replacing unit 107, and transmits the call data for transmission after the preamble signal is superimposed. Is passed to the cryptographic processing unit 109. Specifically, as shown in FIG. 3A, the lower-order predetermined number of bits of the PCM data string 201 forming the transmission call data designated by the key exchange processing unit 114 (the lowest order in FIG. 3A) The bit pattern 202 of the bit LSB part) is replaced with the bit pattern 203 of the preamble signal designated by the key exchange processing unit 114. Thereby, the preamble signal is superimposed on the transmission call data. Data other than the call data for transmission designated by the key exchange processing unit 114 is transferred to the encryption processing unit 109 as it is.

  The encryption processing unit 109 encrypts data sequentially output from the preamble superimposing unit 108 in accordance with an instruction from the key exchange processing unit 114, and passes the encrypted data to the RTP processing unit 104. When there is no instruction from the key exchange processing unit 114, the data sequentially output from the preamble superimposing unit 108 is passed to the RTP processing unit 104 as it is.

  The decryption processing unit 110 decrypts the received call data (payload data of the RTP packet) sequentially output from the RTP processing unit 104 in accordance with an instruction from the key exchange processing unit 114 and passes this decrypted data to the key data extraction unit 111. . When there is no instruction from the key exchange processing unit 114, the received call data sequentially output from the RTP processing unit 104 is passed to the key data extraction unit 111 as it is.

  The key data extraction unit 111 passes the received call data specified by the key exchange processing unit 114 among the received call data sequentially output from the decryption processing unit 110 to the key exchange processing unit 114 as key data. The received call data other than the received call data specified by the key exchange processing unit 114 is passed to the preamble detection unit 112.

  The preamble detection unit 112 passes received call data sequentially output from the key data extraction unit 111 to the call data interpolation unit 113, and detects received call data on which a preamble signal is superimposed from the received call data. The key exchange processing unit 114 is notified of the detection result.

  The call data interpolation unit 113 passes the received call data sequentially output from the preamble detection unit 112 to the voice CODEC 106, and receives the received call data lost due to the replacement with the key data by the partner terminal according to the instruction of the key exchange processing unit 114. And pass it to the audio CODEC 106. Specifically, the received call data immediately before the received call data replaced with the key data is copied and inserted at the position where the key data was present. Alternatively, the received call data lost by the replacement with the key data is predicted from a plurality of received call data immediately before the received call data replaced with the key data, and inserted at the position where the key data was present. .

  The key exchange processing unit 114, in accordance with an instruction received from the user via the man-machine IF unit 102, a key data replacement unit 107, a preamble superimposing unit 108, an encryption processing unit 109, a decryption processing unit 110, a key data extraction unit 111, a preamble The detecting unit 112 and the call data interpolating unit 113 are controlled to perform key exchange with the partner terminal to which the SIP session is connected. Then, the cryptographic processing unit 109 and the decryption processing unit 110 are controlled to perform cryptographic communication with the counterpart terminal via this SIP session.

  4 and 5 are flowcharts for explaining the key exchange process of IP telephone terminal 1 according to the first embodiment of the present invention. This flow starts when a SIP session is established with a partner terminal and a call (transmission / reception of an RTP packet) is started.

  When the key exchange processing unit 114 receives an encrypted communication start operation from the user via the man-machine IF unit 102 (YES in S100), the key transmission processing unit 114 sends the latest transmission call data output from the voice CODEC 106 to the preamble superimposing unit 108. The instruction for superimposing the investigation preamble signal with the designation of is output. In response to this, the preamble superimposing unit 108 adds a predetermined amount of transmission call data designated by the key exchange processing unit 114 to the transmission call data specified by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 via the key data replacement unit 107. A survey preamble signal having a bit pattern is superimposed (S101). The transmission call data on which the investigation preamble signal is superimposed is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Here, the preamble detection unit 112 determines whether or not the preamble signal is superimposed on the received call data received from the counterpart terminal via the communication IF unit 101 and extracted from the RTP packet payload by the RTP processing unit 104. I'm researching. After transmitting the call data for transmission on which the investigation preamble signal is superimposed (S101), the preamble detector 112 has superimposed the response preamble signal having a predetermined bit pattern within a predetermined time T1 (for example, 3 seconds). When the received call data is not detected (NO in S102), the key exchange processing unit 114 determines that the partner terminal does not support encryption communication, and displays a man machine indicating that the partner terminal does not support encryption communication. The process is performed on the IF unit 102 (S103). Then return to the start.

  On the other hand, after transmission of the transmission call data on which the investigation preamble signal is superimposed (S101), the preamble detection unit 112 receives the reception call data on which the response preamble signal having a predetermined bit pattern is superimposed within the predetermined time T1. Is detected (YES in S102), the key exchange processing unit 114 determines that the partner terminal supports encryption communication, and causes the key data extraction unit 111 to send the received call data after Xth (X is a predetermined value). The received call data output from the RTP processing unit 104 is specified immediately after (for example, immediately after (X = 1)), and the acquisition of the public key data (the other party's public key data) of the other terminal is instructed.

  In response to this, the key data extraction unit 111 acquires the received call data output from the RTP processing unit 104 Xth after the received call data on which the response preamble signal is superimposed, as the other party's public key data. The key data is transferred to the key exchange processing unit 114 without being sent to the preamble detection unit 112 (S104). In response to this, the key exchange processing unit 114 passes the partner public key data to the encryption processing unit 109.

  Next, the key exchange processing unit 114 designates the received call data output from the RTP processing unit 104 immediately before the partner public key data to the call data interpolation unit 113, and is replaced with the partner public key data by the partner terminal. Instructs interpolation of received call data. In response to this, the call data interpolation unit 113 generates received call data lost due to the replacement with the other party public key data, and inserts the generated received call data immediately after the specified received call data. And output to the audio CODEC 106 (S105).

  Next, the key exchange processing unit 114 checks whether or not the transmission call data sequentially output from the voice CODEC 106 includes the transmission call data for the silent period. Then, after detecting the received call data on which the response preamble signal is superimposed (S102), if the transmission call data in the silent period is detected within a predetermined time T2 (for example, 1 second, T2 <T1), the preamble is superimposed. An instruction to superimpose a synchronization preamble signal accompanied by designation of the transmission call data output from the voice CODEC 106 X times before the transmission call data in the silent period is output to the unit 108. On the other hand, if the transmission call data for the silent period cannot be detected, an instruction to superimpose the synchronization preamble signal accompanied by the designation of the latest transmission call data output from the voice CODEC 106 is output to the preamble superimposing unit 108. To do.

  In response to this, the preamble superimposing unit 108 adds a predetermined amount of transmission call data designated by the key exchange processing unit 114 to the transmission call data specified by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 via the key data replacement unit 107. A synchronization preamble signal having a bit pattern is superimposed (S106). The transmission call data on which the synchronization preamble signal is superimposed is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Next, the key exchange processing unit 114 transmits to the key data replacement unit 107 the designation of the transmission call data output from the voice CODEC 106 after Xth of the transmission call data on which the synchronization preamble signal is superimposed. The instruction to replace the public key data (self-public key data) is output. In response to this, the key data replacement unit 107 uses the transmission call data designated by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106, as self-public key data registered in advance. (S107). This self-public key data is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Next, the key exchange processing unit 114 checks whether or not the transmission call data sequentially output from the voice CODEC 106 includes the transmission call data for the silent period. Then, after transmitting the call data for transmission on which the synchronization preamble signal is superimposed (S106), if the call data for transmission in the silent period is detected within a predetermined time T2, the silent period is sent to the preamble superimposing unit 108. An instruction to superimpose a synchronization preamble signal accompanied by designation of transmission call data output from the voice CODEC 106 before the Xth transmission call data is output. On the other hand, if the transmission call data for the silent period cannot be detected, an instruction to superimpose the synchronization preamble signal accompanied by the designation of the latest transmission call data output from the voice CODEC 106 is output to the preamble superimposing unit 108. To do.

  In response to this, the preamble superimposing unit 108 adds a predetermined amount of transmission call data designated by the key exchange processing unit 114 to the transmission call data specified by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 via the key data replacement unit 107. A synchronization preamble signal having a bit pattern is superimposed (S108). The transmission call data on which the synchronization preamble signal is superimposed is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Next, the key exchange processing unit 114 sends to the key data replacement unit 107 the designation of the transmission call data output from the voice CODEC 106 after Xth of the transmission call data on which the synchronization preamble signal is superimposed. A replacement instruction for the common key data (self-common key data) is output. In addition, the encryption processing unit 109 outputs an encryption instruction using the other party's public key data accompanied by designation of the self-common key data.

  In response to this, the key data replacement unit 107 uses the transmission call data designated by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 as the self-common key data registered in advance. (S109). Also, the encryption processing unit 109 encrypts the self-common key data with the partner public key data (S110). The encrypted self-shared key data is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Here, the preamble detection unit 112 checks whether the preamble signal is superimposed on the received call data received from the counterpart terminal via the communication IF unit 101 and extracted from the RTP packet payload by the RTP processing unit 104. ing. After transmission of the call data for transmission on which the synchronization preamble signal is superimposed (S108), the preamble detection unit 112 has a synchronization preamble having a predetermined bit pattern within a predetermined time T3 (for example, 3 seconds, T3> T2). If the received call data with the superimposed signal is not detected (NO in S111), the key exchange processing unit 114 determines that an error has occurred in the key exchange procedure, and displays an error display on the man-machine IF unit 102. (S112). Then return to the start.

  On the other hand, after transmitting the transmission call data on which the synchronization preamble signal is superimposed (S108), the preamble detection unit 112 receives the reception call data on which the synchronization preamble signal having a predetermined bit pattern is superimposed within the predetermined time T3. Is detected (YES in S111), the key exchange processing unit 114 receives, for the decryption processing unit 110, the received call output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed. Outputs a decryption instruction using its own private key data (self-secret key data) with data designation. In addition, the key data extraction unit 111 specifies the common key data of the partner terminal (partner) with designation of the reception call data output from the RTP processing unit 104 after Xth of the reception call data on which the synchronization preamble signal is superimposed. (Common key data) acquisition instruction is output.

  In response, the decryption processing unit 110 uses the pre-registered self-secret key data to receive the received call data output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed. Is decrypted (S113). Further, the key data extraction unit 111 obtains the received call data output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed and decrypted by the decryption processing unit 110 as the partner common key data. Then, the partner common key data is transferred to the key exchange processing unit 114 without being sent to the voice CODEC 106 (S114). In response to this, the key exchange processing unit 114 passes the partner common key data to the decryption processing unit 110.

  Next, the key exchange processing unit 114 designates the received call data output from the RTP processing unit 104 immediately before the partner common key data in the call data interpolation unit 113 and is replaced with the partner common key data by the partner terminal. Instructs interpolation of received call data. In response to this, the call data interpolation unit 113 generates received call data lost due to the replacement with the partner common key data, and inserts the generated received call data immediately after the specified received call data. And output to the audio CODEC 106 (S115).

  Thereafter, the key exchange processing unit 114 instructs the encryption processing unit 109 to perform encryption using the self-common key data, and instructs the decryption processing unit 110 to perform decryption using the partner common key data. To do. In response to this, the encryption processing unit 109 encrypts the call data for transmission sequentially output from the voice CODEC 106 using the self-common key data. The encrypted call data for transmission is stored in the RTP packet by the RTP processing unit 104 and sequentially transmitted from the communication IF unit 101 to the partner terminal. Also, the decryption processing unit 110 decrypts the received communication data received from the partner terminal via the communication IF unit 101 and extracted from the RTP packet by the RTP processing unit 104 using the partner common key data. These decoded received call data are sequentially input to the voice CODEC 106 and output from the man-machine IF unit 102. As described above, encrypted communication with the counterpart terminal is started (S116), and this flow ends.

  The preamble detection unit 112 checks whether or not the preamble signal is superimposed on the received call data received from the counterpart terminal via the communication IF unit 101 and extracted from the RTP packet payload by the RTP processing unit 104. Yes. When the preamble detection unit 112 detects received call data on which a survey preamble signal having a predetermined bit pattern is superimposed (YES in S120), the key exchange processing unit 114 transmits the preamble superimposition unit 108 to the speech CODEC 106. An instruction to superimpose a response preamble signal is output along with the designation of the latest output call data for transmission. In response to this, the preamble superimposing unit 108 adds a predetermined amount of transmission call data designated by the key exchange processing unit 114 to the transmission call data specified by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 via the key data replacement unit 107. A response preamble signal having a bit pattern is superimposed (S121). The transmission call data on which the response preamble signal is superimposed is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Next, the key exchange processing unit 114 sends to the key data replacement unit 107 self-designation with designation of transmission call data output from the voice CODEC 106 after Xth of the transmission call data on which the response preamble signal is superimposed. Outputs public key data replacement instructions. In response to this, the key data replacement unit 107 uses the transmission call data designated by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106, as self-public key data registered in advance. (S122). This self-public key data is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Here, the preamble detection unit 112 checks whether the preamble signal is superimposed on the received call data received from the counterpart terminal via the communication IF unit 101 and extracted from the RTP packet payload by the RTP processing unit 104. ing. After transmission of the call data for transmission on which the response preamble signal is superimposed (S121), within a predetermined time T3, the preamble detector 112 detects the received call data on which the synchronization preamble signal having a predetermined bit pattern is superimposed. If not (NO in S123), the key exchange processing unit 114 determines that there is no encryption communication request from the counterpart terminal, and returns to the start.

  On the other hand, after transmitting the transmission call data on which the response preamble signal is superimposed (S121), the preamble detection unit 112 receives the received call data on which the synchronization preamble signal having a predetermined bit pattern is superimposed within the predetermined time T3. Is detected (YES in S123), the key exchange processing unit 114 receives from the RTP processing unit 104 after the Xth of the received call data on which the synchronization preamble signal is superimposed. Outputs an instruction to acquire the other party's public key data with call data specification. In response to this, the key data extraction unit 111 acquires the received call data output from the RTP processing unit 104 Xth after the received call data on which the synchronization preamble signal is superimposed, as the other party's public key data. The key data is transferred to the key exchange processing unit 114 without being sent to the voice CODEC 106 (S124). In response to this, the key exchange processing unit 114 passes the partner public key data to the encryption processing unit 109.

  Next, the key exchange processing unit 114 designates the received call data output from the RTP processing unit 104 immediately before the partner public key data to the call data interpolation unit 113, and is replaced with the partner public key data by the partner terminal. Instructs interpolation of received call data. In response to this, the call data interpolation unit 113 generates received call data lost due to the replacement with the other party public key data, and inserts the generated received call data immediately after the specified received call data. And output to the audio CODEC 106 (S125).

  Here, the preamble detection unit 112 checks whether the preamble signal is superimposed on the received call data received from the counterpart terminal via the communication IF unit 101 and extracted from the RTP packet payload by the RTP processing unit 104. ing. After detecting the received call data on which the synchronization preamble signal is superimposed (S123), the preamble detector 112 detects the received call data on which the synchronization preamble signal having a predetermined bit pattern is superimposed within a predetermined time T3. If not (NO in S126), the key exchange processing unit 114 determines that some error has occurred in the key exchange procedure, and returns to the start.

  On the other hand, after detecting the received call data on which the synchronization preamble signal is superimposed (S123), within a predetermined time T3, the preamble detector 112 receives the received call data on which the synchronization preamble signal having a predetermined bit pattern is superimposed. If detected (YES in S126), the key exchange processing unit 114 receives the received call data output from the RTP processing unit 104 after the Xth received call data on which the synchronization preamble signal is superimposed, to the decryption processing unit 110. An instruction for decryption using self-secret key data is output. In addition, the key data extraction unit 111 is instructed to acquire the other party common key data with the designation of the received call data output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed. Output.

  In response, the decryption processing unit 110 uses the pre-registered self-secret key data to receive the received call data output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed. Is decrypted (S127). Further, the key data extraction unit 111 obtains the received call data output from the RTP processing unit 104 after Xth of the received call data on which the synchronization preamble signal is superimposed and decrypted by the decryption processing unit 110 as the partner common key data. Then, the partner common key data is transferred to the key exchange processing unit 114 without being sent to the voice CODEC 106 (S128). In response to this, the key exchange processing unit 114 passes the partner common key data to the decryption processing unit 110.

  Next, the key exchange processing unit 114 designates the received call data output from the RTP processing unit 104 immediately before the partner common key data in the call data interpolation unit 113 and is replaced with the partner common key data by the partner terminal. Instructs interpolation of received call data. In response to this, the call data interpolation unit 113 generates received call data lost due to the replacement with the partner common key data, and inserts the generated received call data immediately after the specified received call data. And output to the audio CODEC 106 (S129).

  Next, the key exchange processing unit 114 checks whether or not the transmission call data sequentially output from the voice CODEC 106 includes the transmission call data for the silent period. Then, after detecting the received call data on which the synchronization preamble signal is superimposed (S126), if the transmission call data for the silent period is detected within the predetermined time T2, the silent period is transmitted to the preamble superimposing unit 108. An instruction to superimpose a synchronization preamble signal accompanied by designation of the transmission call data output from the voice CODEC 106 Xth before the transmission call data is output. On the other hand, if the transmission call data for the silent period cannot be detected, the preamble superimposing unit 108 is instructed to superimpose the synchronization preamble signal with the designation of the latest transmission call data output from the voice CODEC 106. Output.

  In response to this, the preamble superimposing unit 108 adds a predetermined amount of transmission call data designated by the key exchange processing unit 114 to the transmission call data specified by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 via the key data replacement unit 107. A synchronization preamble signal having a bit pattern is superimposed (S130). The transmission call data on which the synchronization preamble signal is superimposed is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Next, the key exchange processing unit 114 is accompanied by the designation of the call data for transmission output from the voice CODEC 106 after the Xth of the call data for transmission on which the synchronization preamble signal is superimposed, to the key data replacement unit 107. Outputs a replacement instruction for self-common key data. In addition, the encryption processing unit 109 outputs an encryption instruction using the other party's public key data accompanied by designation of the self-common key data.

  In response to this, the key data replacement unit 107 uses the transmission call data designated by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106 as the self-common key data registered in advance. (S131). Further, the encryption processing unit 109 encrypts the self-common key data with the partner public key data (S132). The encrypted self-shared key data is stored in the RTP packet by the RTP processing unit 104 and transmitted from the communication IF unit 101 to the partner terminal.

  Thereafter, the key exchange processing unit 114 instructs the encryption processing unit 109 to perform encryption using the self-common key data, and instructs the decryption processing unit 110 to perform decryption using the partner common key data. To do. In response to this, the encryption processing unit 109 encrypts the call data for transmission sequentially output from the voice CODEC 106 using the self-common key data. The encrypted call data for transmission is stored in the RTP packet by the RTP processing unit 104 and sequentially transmitted from the communication IF unit 101 to the partner terminal. Also, the decryption processing unit 110 decrypts the received communication data received from the partner terminal via the communication IF unit 101 and extracted from the RTP packet by the RTP processing unit 104 using the partner common key data. These decoded received call data are sequentially input to the voice CODEC 106 and output from the man-machine IF unit 102. As described above, encrypted communication with the counterpart terminal is started (S116), and this flow ends.

  Next, the key exchange operation in the communication system that transmits and receives RTP packets between the IP telephone terminals 1 according to the first embodiment of the present invention will be described.

  FIG. 6 is a sequence diagram for explaining the key exchange operation between the IP telephone terminals 1 according to the first embodiment of the present invention connected via the gateway 2 that terminates the RTP layer. Here, in order to identify the two IP telephone terminals 1, a branch number is given to the code of each IP telephone terminal 1.

  A SIP session is established between the IP telephone terminal 1-1 and the IP telephone terminal 1-2 via the gateway 2, and the call data 3-1 and 3-2 are transferred to the payload of the RTP packet via the SIP session. Assume that they are stored and sent and received. In addition, it is assumed that the predetermined data is inserted after the Xth of the investigation preamble signal, the response preamble signal, and the synchronization preamble signal between the communication terminals 1-1 and 1-2 (FIG. 6). Then immediately after: X = 1). Alternatively, the Xth numerical information may be transmitted by including the Xth numerical information (for example, treating the lower 3 bits as a numerical value) in the preamble signal.

  First, it is assumed that the IP telephone terminal 1-1 receives an encrypted communication start operation from the user. The IP telephone terminal 1-1 superimposes the investigation preamble signal 4-1 on the arbitrary telephone call data 3-1, among the telephone call data 3-1, which is sequentially transmitted to the IP telephone terminal 1-2 (S201). These call data 3-1 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-2 via the gateway 2.

  Next, the IP telephone terminal 1-2 detects the call data 3-1 on which the investigation preamble signal 4-1 is superimposed from the call data 3-1 sequentially received from the IP telephone terminal 1-1 (S202). In response to the silent call data 3-2 transmitted to the IP telephone terminal 1-1 within the predetermined time T2, or the latest call data 3-2 transmitted to the IP telephone terminal 1-1 after the predetermined time T2 elapses. The preamble signal 4-2 is superimposed (S203). Further, the call data 3-2 scheduled to be transmitted after Xth of the call data 3-2 on which the response preamble signal 4-2 is superimposed (immediately in FIG. 6, X = 1) is replaced with the self-public key data 6-2. (S204). The call data 3-2 and the self-public key data 6-2 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-1 via the gateway 2.

  Next, the IP telephone terminal 1-1 receives the call data 3-2 sequentially received from the IP telephone terminal 1-2 within a predetermined time T1 after transmission of the call data 3-1 on which the investigation preamble signal 4-1 is superimposed. When the call data 3-2 on which the response preamble signal 4-2 is superimposed is detected (S205), the call data 6-2 received after the Xth of the call data 3-2 is converted into the other party public key data 6-2. (S206). Further, the lost telephone call data 3-2 is replaced by the partner telephone exchange key data 6-2 by the IP telephone terminal 1-2 (S207).

  Next, the IP telephone terminal 1-1 transmits to the IP telephone terminal 1-2 a silent section that is transmitted within a predetermined time T2 after detecting the call data 3-2 on which the response preamble signal 4-2 is superimposed. The synchronization preamble signal 5-1 is superimposed on the call data 3-1 or the latest call data 3-1 transmitted after a predetermined time T2 has elapsed (S208). Further, the call data 3-1 scheduled to be transmitted after Xth of the call data 3-1 superimposed with the synchronization preamble signal 5-1 is replaced with the self-public key data 6-1 (S209). These call data 3-1 and self-public key data 6-1 are respectively stored in the payload of the RTP packet, and are sequentially transmitted to the IP telephone terminal 1-2 via the gateway 2.

  Next, the IP telephone terminal 1-2 sequentially receives the call data 3- received from the IP telephone terminal 1-1 within a predetermined time T3 after transmission of the call data 3-2 on which the response preamble signal 4-2 is superimposed. When the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed is detected from 1 (S210), the call data 6-1 received Xth after the call data 3-1 is detected as the partner public key data 6-. 1 is acquired (S211). Further, the call data 3-1 that has been replaced by the partner exchange key data 6-1 and lost by the IP telephone terminal 1-1 is interpolated (S212).

  Next, the IP telephone terminal 1-1 transmits the call data 3 in the silent section to be transmitted to the IP telephone terminal 1-2 within a predetermined time T2 after the transmission of the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed. −1, or the latest preamble data 5-1 to be transmitted to the IP telephone terminal 1-2 after the elapse of a predetermined time T2 is superimposed on the synchronization preamble signal 5-1 (S213). Further, the call data 3-1 scheduled to be transmitted after Xth of the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed is replaced with the self-common key data 7-1 (S214). These call data 3-1 and self-common key data 7-1 are each stored in the payload of the RTP packet, and sequentially transmitted to the IP telephone terminal 1-2 via the gateway 2.

  Next, the IP telephone terminal 1-2 receives the call data 3-sequentially received from the IP telephone terminal 1-1 within a predetermined time T3 after the detection of the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed. 1, when new call data 3-1 on which the synchronization preamble signal 5-1 is superimposed is detected (S215), the call data 7-1 received after Xth of the call data 3-1 is used as the partner common key data. Obtained as 7-1 (S216). In addition, the telephone call data 3-1 that has been replaced with the partner common key data 7-1 by the IP telephone terminal 1-1 and lost is interpolated (S217).

  Next, the IP telephone terminal 1-2 transmits the call data 3 in the silent section to be transmitted to the IP telephone terminal 1-1 within a predetermined time T2 after detecting the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed. -2 or the latest preamble data 5-2 transmitted to the IP telephone terminal 1-1 after the elapse of the predetermined time T2 is superimposed on the synchronization preamble signal 5-2 (S218). Further, the call data 3-2 scheduled to be transmitted after Xth of the call data 3-2 on which the synchronization preamble signal 5-2 is superimposed is replaced with the self-common key data 7-2 (S219). The call data 3-2 and the self-common key data 7-2 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-1 via the gateway 2.

  Next, the IP telephone terminal 1-1 receives the call data 3-1 sequentially received from the IP telephone terminal 1-2 within a predetermined time T 3 after transmission of the call data 3-1 on which the synchronization preamble signal 5-1 is superimposed. 2, when new call data 3-2 on which the synchronization preamble signal 5-2 is superimposed is detected (S220), the data received after Xth of the call data 3-2 is used as the partner common key data 7-2. Obtain (S221). Further, the lost telephone call data 3-2, which is replaced with the partner common key data 7-2 by the IP telephone terminal 1-2, is interpolated (S222).

  Thereafter, the IP telephone terminals 1-1 and 1-2 start encryption communication using the shared common key data 7-1 and 7-2 (S 223). Specifically, the IP telephone terminal 1-1 encrypts the call data 3-1 to be sequentially transmitted to the IP telephone terminal 1-2 using the self-common key data 7-1. These encrypted call data 3-1 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-2 via the gateway 2. Also, the IP telephone terminal 1-1 uses the partner common key data 7-2 to decrypt the encrypted call data 3-2 that is sequentially received from the IP telephone terminal 1-2. On the other hand, the IP telephone terminal 1-2 encrypts the call data 3-2 to be sequentially transmitted to the IP telephone terminal 1-1 using the self-common key data 7-2. These encrypted call data 3-2 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-1 via the gateway 2. Also, the IP telephone terminal 1-2 uses the partner common key data 7-1 to decrypt the encrypted call data 3-1, which is sequentially received from the IP telephone terminal 1-1.

  The first embodiment of the present invention has been described above.

  In the present embodiment, the IP telephone terminal 1 superimposes a preamble signal on transmission call data stored in the payload of the RTP packet, transmits the RTP packet, and transmits the RTP packet from the RTP packet on which the preamble signal is superimposed. The transmission call data stored in the payload of the next RTP packet is replaced with key data, and the RTP packet in which this payload is replaced with the key data is transmitted. In addition, the IP telephone terminal 1 tries to detect a preamble signal superimposed on the received call data stored in the payload of the received RTP packet. If the preamble signal is successfully detected, the key data is extracted from the payload of the RTP packet received Xth after the RTP packet in which the preamble signal is detected.

  Therefore, according to the present embodiment, it is possible to transmit and receive call data and key data between IP telephone terminals 1 without increasing the network load even in a network environment in which the gateway 2 that terminates the RTP layer is interposed. it can.

  In this embodiment, as shown in FIG. 3 (A), IP telephone terminal 1 uses bit pattern 202 in the lower predetermined number of bits of PCM data string 201 forming transmission call data as a predetermined bit pattern. By changing to 203, the preamble signal is superimposed on the call data for transmission. Further, the IP telephone terminal 1 receives the received call data in which the lower predetermined number of bits of the PCM data string 201 forming the received call data stored in the payload of the received RTP packet is a predetermined bit pattern 203, It is detected as received call data on which a preamble signal is superimposed.

  Therefore, according to the present embodiment, it is possible to suppress deterioration in the quality of the call data and to transmit / receive the preamble signal between the IP telephone terminals 1 without generating a large noise in the call data.

  In the present embodiment, the IP telephone terminal 1 receives the received call data replaced by the key data by the partner terminal, the RTP packet received immediately before the RTP packet storing the key data, or just before this Interpolation is performed based on received call data stored in payloads of a plurality of received RTP packets. Therefore, according to the present embodiment, it is possible to prevent interruption of sound in reproduction of received call data due to reception of key data.

  Further, in the present embodiment, the IP telephone terminal 1 determines that when any transmission call data stored in the payload of the RTP packet transmitted after the Xth of the arbitrary RTP packet is a silent section, A preamble signal is superimposed on the call data for transmission stored in the payload. Therefore, according to the present embodiment, the call data for transmission to be replaced with the key data becomes the voice data in the silent period, so that the influence of the loss of the call data for transmission due to the replacement of the key data can be reduced.

<Second embodiment>
FIG. 7 is a schematic diagram of an IP telephone terminal 1a according to the second embodiment of the present invention.

  Here, components having the same functions as those of the IP telephone terminal 1 according to the first embodiment shown in FIG.

  As shown in the figure, the IP telephone terminal 1a according to the present embodiment is different from the IP telephone terminal 1 according to the first embodiment shown in FIG. Instead of the CODEC 106, the key data replacement unit 107, the preamble superimposition unit 108, the key data extraction unit 111, and the preamble detection unit 112, the voice CODEC 106a, the key data replacement unit 107a, the preamble superposition unit 108a, the key data extraction unit 111a, and the preamble That is, the detection unit 112a is provided.

  The voice CODEC 106a is a G.C. This codec performs encoding and decoding of audio signals in accordance with 711.1. Here, G. 711.1 is a G. This encoding method is compatible with H.711.

  Specifically, the telephone band of the analog voice signal input from the man-machine IF unit 102 is converted into 8-bit PCM data, and the additional band (low band or high band) is converted into 4-bit PCM data. . Then, a total of 12 bits of PCM data consisting of the upper 8 bits of PCM data (standard bit area) representing the telephone band and the lower 4 bits of PCM data (extension bit area) representing the additional band are stored in the payload of the RTP packet. For each data length (PCM data string) to be transmitted, the data is sequentially output as call data for transmission.

  Also, the incoming call data that is sequentially input is converted into an analog voice signal and output from the man-machine IF unit 102. Here, if the PCM data constituting the received call data (PCM data string) is 12 bits, the upper 8 bits of PCM data is decoded into a telephone band audio signal, and the lower 4 bits of PCM data are added to the additional band audio. An audio signal obtained by decoding the signal and synthesizing both is output from the man-machine IF unit 102. On the other hand, if the PCM data constituting the received call data is 8 bits, the PCM data is decoded into a voice signal in the telephone band and output from the man-machine IF unit 102.

  The key data replacement unit 107a uses the transmission call data designated by the key exchange processing unit 114 among the transmission call data sequentially output from the voice CODEC 106a, for example, as shown in FIG. The standard bit area 306 of the PCM data string 305 constituting the call data is left as it is, and only the extension bit area 307 is changed to the key data type (public key or common key) and attribute (RSA method or DES method). ) And key data 310 including the key data main body 309, and passes to the preamble superimposing unit 108a. The transmission call data other than the transmission call data designated by the key exchange processing unit 114 is directly passed to the preamble superimposing unit 108a.

  The preamble superimposing unit 108a superimposes the preamble signal on the transmission call data designated by the key exchange processing unit 114 among the data sequentially output from the key data replacing unit 107a, and transmits the call data for transmission after the preamble signal is superimposed. Is passed to the cryptographic processing unit 109. Specifically, as shown in FIG. 3 (B), a predetermined number of lower-order bits in the extended bit area 207 or the standard bit area 206 of the PCM data sequence 205 forming the call data for transmission designated by the key exchange processing unit 114 The bit pattern 208 of the portion (the 8th bit of the standard bit area 206 in FIG. 3B) is replaced with the bit pattern 209 of the preamble signal designated by the key exchange processing unit 114. Thereby, the preamble signal is superimposed on the transmission call data. Note that since the extension bit area 207 has a small number of bits, it is preferable to replace the lower predetermined number of bits in the standard bit area 206 with the bit pattern of the preamble signal in consideration of the influence on the quality of the call data. Data other than the call data for transmission designated by the key exchange processing unit 114 is transferred to the encryption processing unit 109 as it is.

  The key data extraction unit 111a includes a PCM bit data string 305 (see FIG. 2B) that constitutes the received call data designated by the key exchange processing unit 114 among the received call data sequentially output from the decryption processing unit 110. Is divided into a standard bit area 306 and an extended bit area 307. Then, the standard bit area 306 is passed to the preamble detector 112a as received call data, and the extended bit area 307 is passed to the key exchange processor 114 as key data. The received call data other than the received call data specified by the key exchange processing unit 114 is passed to the preamble detection unit 112a as it is.

  The preamble detection unit 112a passes the received call data sequentially output from the key data extraction unit 111a to the voice CODEC 106a, detects the received call data on which the preamble signal is superimposed, from these received call data, The detection result is notified to the key exchange processing unit 114.

  Note that, as described above, the key exchange process of the IP telephone terminal 1a according to the present embodiment includes the preamble signal superimposition / detection method and the key data replacement / extraction method according to the first embodiment of the present invention. Since the call data interpolation unit 113 is omitted in the IP phone terminal 1a according to the present embodiment, which is different from the IP phone terminal 1, interpolation processing of received call data replaced with key data by the counterpart terminal (S105, Except for the absence of S115, S125, and S129), the key exchange process is the same as that of the IP telephone terminal 1 according to the first embodiment of the present invention shown in FIGS.

  Next, a key exchange operation in a communication system that transmits and receives RTP packets between IP telephone terminals 1a according to the second embodiment of the present invention will be described.

  FIG. 8 is a sequence diagram for explaining the key exchange operation between the IP telephone terminals 1a according to the second embodiment of the present invention connected via the gateway 2 that terminates the RTP layer. Here, in order to identify the two IP telephone terminals 1a, a branch number is given to the code of each IP telephone terminal 1a.

  A SIP session is established between the IP telephone terminal 1a-1 and the IP telephone terminal 1a-2 via the gateway 2, and the call data 3a-1, 3a-2 are transferred to the payload of the RTP packet via the SIP session. Assume that they are stored and sent and received.

  First, it is assumed that IP telephone terminal 1a-1 has received an encrypted communication start operation from a user.

  The IP telephone terminal 1a-1 superimposes the investigation preamble signal 4-1 on the standard bit area 3b-1 of any call data 3a-1 among the call data 3a-1 that is sequentially transmitted to the IP telephone terminal 1a-2. (S251). These call data 3a-1 are respectively stored in the payload of the RTP packet, and sequentially transmitted to the IP telephone terminal 1a-2 via the gateway 2.

  Next, the IP telephone terminal 1a-2 receives the call data 3a- in which the investigation preamble signal 4-1 is superimposed on the standard bit area 3b-1 from the call data 3a-1 sequentially received from the IP telephone terminal 1a-1. When 1 is detected (S252), the speech data 3a-2 in the silent section transmitted to the IP telephone terminal 1a-1 within the predetermined time T2, or the latest telephone data transmitted to the IP telephone terminal 1a-1 after the predetermined time T2 has elapsed. The response preamble signal 4-2 is superimposed on the standard bit area 3b-2 of 3a-2 (S253). Further, the extended bit area 3c-2 of the call data 3a-2 scheduled to be transmitted is self-published Xth after the call data 3a-2 on which the response preamble signal 4-2 is superimposed (immediately in FIG. 8, X = 1). Replace with key data 6-2 (S254). These call data 3a-2 are respectively stored in the payload of the RTP packet, and are sequentially transmitted to the IP telephone terminal 1a-1 via the gateway 2.

  Next, the IP telephone terminal 1a-1 sequentially starts from the IP telephone terminal 1a-2 within a predetermined time T1 after the transmission of the call data 3a-1 in which the investigation preamble signal 4-1 is superimposed on the standard bit area 3b-1. When the call data 3a-2 in which the response preamble signal 4-2 is superimposed on the standard bit area 3b-2 is detected from the received call data 3a-2 (S255), the call data 3a-2 is received after Xth. The extended bit area 3c-2 of the call data 3a-2 is acquired as the partner public key data 6-2 (S256). The extension bit area 3c-2 is separated from the call data 3a-2 as the partner public key data 6-2, and only the standard bit area 3b-2 is input to the voice CODEC 106a and decoded into a voice signal in the telephone band.

  Next, the IP telephone terminal 1a-1 transmits to the IP telephone terminal 1a-2 within a predetermined time T2 after detecting the call data 3a-2 in which the response preamble signal 4-2 is superimposed on the standard bit area 3b-2. The synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 of the latest call data 3a-1 to be transmitted to the IP telephone terminal 1a-2 after elapse of the predetermined time T2 (S257).

  Further, the extension bit area 3c-1 of the call data 3a-1 scheduled to be transmitted after the Xth of the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 is used as the self-public key data 6- Replace with 1 (S258). These call data 3a-1 are respectively stored in the payload of the RTP packet, and sequentially transmitted to the IP telephone terminal 1a-2 via the gateway 2.

  Next, the IP telephone terminal 1a-2 sequentially transmits from the IP telephone terminal 1a-1 within a predetermined time T3 after transmission of the call data 3a-2 in which the response preamble signal 4-2 is superimposed on the standard bit area 3b-2. When the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 is detected from the received call data 3a-1 (S259), the call data 3a-1 is received Xth time after the call data 3a-1. The extended bit area 3c-1 of the call data 3a-1 is acquired as the partner public key data 6-1 (S260). The extension bit area 3c-1 is separated from the call data 3a-1 as the partner public key data 6-1, and only the standard bit area 3b-1 is input to the voice CODEC 106a and decoded into a voice signal in the telephone band.

  Next, the IP telephone terminal 1a-1 transmits to the IP telephone terminal 1a-2 within a predetermined time T2 after transmission of the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1. The synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 of the latest call data 3a-1 to be transmitted to the IP telephone terminal 1a-2 after elapse of the predetermined time T2 (S261). Further, the extension bit area 3c-1 of the call data 3a-1 scheduled to be transmitted after the Xth of the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 is assigned to the self-common key data 7- Replace with 1 (S262). These call data 3a-1 are respectively stored in the payload of the RTP packet, and sequentially transmitted to the IP telephone terminal 1a-2 via the gateway 2.

  Next, the IP telephone terminal 1a-2 receives the IP telephone terminal 1a-1 from the IP telephone terminal 1a-1 within a predetermined time T3 after detecting the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1. When the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1 is detected from the call data 3a-1 received sequentially (S263), the call data 3a-1 is Xth after the call data 3a-1. The extension bit area 3c-1 of the received call data 3a-1 is acquired as the partner common key data 7-1 (S264). The extension bit area 3c-1 is separated from the call data 3a-1 as the partner common key data 7-1, and only the standard bit area 3b-1 is input to the voice CODEC 106a and decoded into a voice signal in the telephone band.

  Next, the IP telephone terminal 1a-2 transmits to the IP telephone terminal 1a-1 within a predetermined time T2 after detecting the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1. The synchronization preamble signal 5-2 is superimposed on the call data 3a-2 of the silent section to be transmitted or the standard bit area 3b-2 of the latest call data 3a-2 to be transmitted to the IP telephone terminal 1a-1 after a predetermined time T2. (S265). Further, the extension bit area 3c-2 of the call data 3a-2 scheduled to be transmitted after the Xth of the call data 3a-2 in which the synchronization preamble signal 5-2 is superimposed on the standard bit area 3b-2 is used as the self-common key data 7-. (S266). These call data 3a-2 are respectively stored in the payload of the RTP packet, and are sequentially transmitted to the IP telephone terminal 1a-1 via the gateway 2.

  Next, the IP telephone terminal 1a-1 receives the IP telephone terminal 1a-2 from the IP telephone terminal 1a-2 within a predetermined time T3 after transmission of the call data 3a-1 in which the synchronization preamble signal 5-1 is superimposed on the standard bit area 3b-1. When the call data 3a-2 in which the synchronization preamble signal 5-2 is superimposed on the standard bit area 3b-2 is detected from the call data 3a-2 received sequentially (S267), the Xth time after the call data 3a-2 is detected. The extension bit area 3c-2 of the received call data 3a-2 is acquired as the partner common key data 7-2 (S268). After the extended bit area 3c-2 is separated from the call data 3a-2 as the partner common key data 7-2, only the standard bit area 3b-2 is input to the voice CODEC 106a and decoded into a voice signal in the telephone band. .

  Thereafter, the IP telephone terminals 1a-1 and 1a-2 start encryption communication using the shared common key data 7-1 and 7-2 (S269). Specifically, IP telephone terminal 1a-1 encrypts call data 3a-1 that is sequentially transmitted to IP telephone terminal 1a-2 using self-common key data 7-1. These encrypted call data 3a-1 are respectively stored in the payload of the RTP packet, and sequentially transmitted to the IP telephone terminal 1a-2 via the gateway 2. In addition, IP telephone terminal 1a-1 decrypts encrypted call data 3a-2 that is sequentially received from IP telephone terminal 1a-2, using partner common key data 7-2. On the other hand, IP telephone terminal 1a-2 encrypts call data 3a-2 that is sequentially transmitted to IP telephone terminal 1a-1 using self-common key data 7-2. These encrypted call data 3a-2 are respectively stored in the payload of the RTP packet and sequentially transmitted to the IP telephone terminal 1-1 via the gateway 2. In addition, IP telephone terminal 1a-2 decrypts encrypted call data 3a-1 that is sequentially received from IP telephone terminal 1a-1, using partner common key data 7-1.

  The second embodiment of the present invention has been described above.

  The present embodiment has the following effects in addition to the effects of the first embodiment.

  That is, in the present embodiment, IP telephone terminal 1a, as shown in FIG. 3 (B), lower-order predetermined number of bits in standard bit area 206 or extended bit area 207 of PCM data sequence 205 forming transmission call data. By changing the partial bit data 208 to a predetermined bit pattern 209, the preamble signal is superimposed on the transmission call data. Then, as shown in FIG. 2B, the standard bit area 306 of the PCM data string 305 that forms the transmission call data scheduled to be transmitted after the Xth transmission call data on which the preamble signal is superimposed is left as it is. The bit area 307 is replaced with the key data 310. Further, as shown in FIG. 3B, the IP telephone terminal 1a has a predetermined bit pattern in which the lower-order predetermined number of bits of the standard bit area 206 or the extended bit area 207 of the PCM data string forming the received call data is a predetermined bit pattern. The received call data 209 is detected as received call data on which a preamble signal is superimposed. Then, as shown in FIG. 2B, the extended bit area 307 of the PCM data string 305 forming the received call data received Xth after the received call data on which the preamble signal is superimposed is extracted as key data. To do.

  Therefore, according to the present embodiment, the transmission call data is not lost due to the transmission of the key data. For this reason, although the voice band is temporarily narrowed, quality degradation such as noise and voice distortion can be further suppressed.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist.

  For example, in each of the above embodiments, when the key data is divided into a plurality of RTP packets and transmitted, the call data for transmission in which the preamble signal is superimposed in association with each of these RTP packets. May not be transmitted. In association with the first RTP packet in which the key data is stored, the preamble signal is superimposed on the transmission call data stored in the RTP packet a predetermined number of times before the first RTP packet, and the last RTP packet in which the key data is stored In association with the RTP packet, a plurality of RTP packets in which the key data is stored are continuously generated by superimposing a postamble signal on the call data for transmission stored in the RTP packet after a predetermined number of the last RTP packet. You may make it transmit. By doing so, the number of times the preamble signal and the postamble signal are superimposed can be reduced, so that the quality deterioration of the call data can be further suppressed.

  In each of the above embodiments, the functional configuration of the IP telephone terminals 1 and 1a shown in FIGS. 1 and 7 is hardened by an integrated logic IC such as ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). It may be realized by a computer, or may be realized by a software by a computer such as a DSP (Digital Signal Processor). Alternatively, in a general-purpose computer such as a PC (Personal Computer) equipped with an auxiliary storage device such as a CPU, memory, HDD, DVD-ROM, and a communication interface such as a NIC (Network Interface Card) and a modem, the CPU executes a predetermined program. It may be realized by loading from an auxiliary storage device onto a memory and executing it.

  In each of the above-described embodiments, the case where the key data is transmitted and received together with the call data in the IP telephone terminal 1 that transmits and receives the call data in accordance with RTP has been described as an example. In communication terminals that perform transmission / reception, the present invention can be widely applied when non-stream data such as control information is transmitted / received together with stream data.

  1, 1a: IP phone terminal, 2: gateway, 101: communication IF unit, 102: man-machine IF unit, 103: SIP processing unit, 104: RTP processing unit, 105: telephone function unit, 106, 106a: voice CODEC, 107, 107a: Key data replacement unit, 108, 108a: Preamble superimposition unit, 109: Encryption processing unit, 110: Decryption processing unit, 111, 111a: Key data extraction unit, 112, 112a: Preamble detection unit, 113: Call data Interpolation unit 114: Key exchange processing unit

Claims (3)

A communication device that performs encrypted communication with a partner device of stream data including audio data or video data,
Transmission means for sequentially transmitting packets including the stream data to the counterpart device;
Replacement means for replacing the stream data stored in any of the packets sequentially transmitted by the transmission means with information relating to cryptographic communication;
Receiving means for sequentially receiving packets including the stream data sequentially transmitted from the counterpart device;
Extraction means for extracting information related to the encrypted communication from any of the packets sequentially received by the receiving means;
Key exchange means for exchanging key data used for encrypted communication with the counterpart device;
Cryptographic communication means for performing cryptographic communication of the stream data with the counterpart device using the key data exchanged by the key exchange means,
The key exchange means is
When starting the encrypted communication, information for notifying that the key exchange is started is stored in the predetermined packet transmitted by the transmitting unit as the information related to the encrypted communication in the replacing unit. If the public key of the counterpart device is extracted as the information related to the encryption communication by the extraction means, the public key of the communication device is used as the information related to the encryption communication. And replacing the stream data stored in the predetermined packet transmitted by the transmitting means, encrypting the common key of the own communication device using the public key of the counterpart device, and encrypting the own communication device The common key is replaced with the stream data stored in the predetermined packet transmitted by the transmitting unit, as information related to the encrypted communication, in the replacing unit Then,
When the information for notifying that the key exchange is started is extracted as the information related to the encrypted communication by the extracting means, the public key of the communication apparatus is used as the information related to the encrypted communication, and the replacing means If the public key of the counterpart device is extracted as information related to the encrypted communication by the extraction means by replacing the stream data stored in the predetermined packet transmitted by the transmission means, the own communication apparatus Is encrypted using the public key of the counterpart device, and the encrypted common key of the communication device is transmitted to the replacement unit as the information related to the encrypted communication. Replacing the stream data stored in the packet of
When the common key of the counterpart device encrypted as information related to the encrypted communication is extracted by the extraction means, the encrypted common key of the counterpart device is decrypted using the private key of the local communication device And
The encryption communication means includes
Encryption of the stream data stored in packets sequentially transmitted by the transmission means, using the common key of the own communication device exchanged with the counterpart device by the key exchange means and the common key of the counterpart device; and A communication apparatus that decodes the stream data stored in packets sequentially received by a receiving means. The communication device according to claim 1,
Superimposing means for superimposing a synchronization signal on the stream data stored in any of the packets sequentially transmitted by the transmitting means;
Detecting means for detecting the synchronization signal from the stream data stored in any of the packets sequentially received by the receiving means;
The key exchange means is
A packet transmitted by the transmitting unit after the predetermined number of packets in which the stream data on which the synchronization signal is superimposed by the superimposing unit is stored in the replacing unit is stored in the packet as the predetermined packet. Replacing the stream data with information relating to cryptographic communication;
The extraction means includes
Information related to the encrypted communication is extracted from the packet received by the receiving unit after a predetermined number of packets storing the stream data on which the synchronization signal detected by the detecting unit is superimposed. Communication device. A communication method for performing encrypted communication of stream data including audio data or video data between a first communication device and a second communication device,
The first communication device is:
Replacing the stream data stored in a predetermined packet to be transmitted to the second communication device with information for notifying the start of key exchange;
Extracting the public key of the second communication device from the predetermined packet received from the second communication device;
Replacing the stream data stored in a predetermined packet to be transmitted to the second communication device with the public key of the own communication device;
The common key of the local communication device is encrypted using the public key of the second communication device, and the stream data stored in a predetermined packet to be transmitted to the second communication device is converted into the encrypted local key. Replace with the common key of the communication device,
Extracting the encrypted common key of the second communication device from the predetermined packet received from the second communication device, and using the encrypted common key of the second communication device as the secret of the own communication device Decrypt with the key,
From the encryption of the stream data stored in the packet sequentially transmitted to the second communication device using the common key of the own communication device and the common key of the second communication device, and the second communication device Decoding the stream data stored in the sequentially received packets;
The second communication device is
Extracting information for notifying that the key exchange starts from a predetermined packet received from the first communication device;
Replacing the stream data stored in a predetermined packet to be transmitted to the first communication device with the public key of the own communication device;
Extracting the public key of the first communication device from the predetermined packet received from the first communication device;
The common key of the own communication device is encrypted using the public key of the first communication device, and the stream data stored in a predetermined packet to be transmitted to the first communication device is converted into the encrypted own key. Replace with the common key of the communication device,
Extracting the encrypted common key of the first communication device from the predetermined packet received from the first communication device, and using the encrypted common key of the first communication device as a secret of the own communication device Decrypt with the key,
From the first communication device, the encryption of the stream data stored in the packet sequentially transmitted to the first communication device using the common key of the own communication device and the common key of the first communication device A communication method, comprising: decoding the stream data stored in sequentially received packets.

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