JP2011066468A - Communication terminal device, communication control method for communication terminal device and communication control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication terminal device unfailingly delivering key information to an opposite party's terminal before the arrival of encrypted data to the opposite party's terminal, and also to provide a communication control method for the communication terminal device, and a communication control program. <P>SOLUTION: When key exchange starts on an opposite party's conference terminal 4 to perform encrypted communication, a conference terminal 3 considers a half of a communication time between transmission of INVITE to the conference terminal 4 and return of Ringing as an arrival time required for reaching of the data from the conference terminal 3 to the conference terminal 4. Then, the key information is added to ACK and transmits to the conference terminal 4, and after the arrival time elapses, the encrypted data are transmitted. In this way, the encrypted audio/video data are prevented from reaching the conference terminal 4 before the key information, irrespective of the network condition of the Internet. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a communication terminal device, a communication control method for a communication terminal device, and a communication control program. Specifically, the present invention is used in a system using SIP and encrypts data encrypted with a partner terminal via a network. The present invention relates to a communication terminal device having a function of transmitting and receiving, a communication control method for the communication terminal device, and a communication control program.

  2. Description of the Related Art Conventionally, a communication device that is used in a system using SIP (Session Initiation Protocol) and has a function of transmitting and receiving data to and from a partner terminal via a network is known (for example, see Patent Document 1). . In such a communication device, when performing encrypted communication with a client, it is necessary to exchange key information used for encryption between the clients. Several protocols for exchanging key information have been proposed. For example, a protocol called SDES (Session Description Protocol Security for Media Streams) is known.

  This SDES is a protocol for exchanging keys between clients by writing encryption key information in the SDP attached to the SIP message. When audio / video data is transmitted to the other party using such a protocol, the data is encrypted using the key information transmitted to the other party. In this case, in order to decrypt the received encrypted audio / video data, it is necessary to receive key information from the other party first.

JP 2006-31125 A

  However, when the key information is exchanged from the side where the call request is “INVITE”, the transmission of the audio / video data is started without confirming whether the key information of the “INVITE” side has arrived at the other side. It will be. Depending on network conditions, encrypted audio / video data may arrive before the key information. In this case, there is a problem that the data cannot be decrypted because the key information has not yet arrived.

  Also, in a video conference system that conducts a remote conference by transmitting and receiving video and audio between terminals, video data is transmitted and received in I and P pictures, so if an I picture is included in a portion that cannot be decoded, There is also a problem that it is impossible to reproduce a video for a long time because a P picture that is a video cannot be decoded with reference to an I picture.

  The present invention has been made to solve the above-described problem, and is capable of reliably delivering key information before encrypted data reaches the partner terminal, and communication control of the communication terminal apparatus. It is an object to provide a method and a communication control program.

  The communication terminal device according to the first aspect of the present invention is a communication that is used in a system using SIP (Session Initiation Protocol) and has a function of transmitting / receiving encrypted data to / from a partner terminal via a network. A terminal device, a communication start request message transmitting means for transmitting a communication start request message to the counterpart terminal in order to establish a session with the counterpart terminal, and the counterpart that has received the communication start request message A success message receiving means for receiving a success message that is output from the terminal and notifying that the communication start request has been accepted, and information on a key for decrypting the encrypted data when the success message is received. Response message transmission for transmitting a response message with certain key information to the counterpart terminal And encrypted data transmission means for transmitting the encrypted data to the counterpart terminal after waiting on a predetermined condition after the response message is transmitted to the counterpart terminal by the response message transmission means. It has.

  The communication terminal device according to the first aspect is used in a system using SIP (Session Initiation Protocol), and has a function of transmitting / receiving encrypted data to / from a partner terminal via a network. First, the communication start request message transmitting means transmits a communication start request message to the counterpart terminal in order to establish a session with the counterpart terminal. Next, a success message is output from the counterpart terminal that received the communication start request message, and a success message notifying that the communication start request has been accepted is received by the success message receiving means. Further, when the success message is received, the response message transmitting means transmits a response message to which the key information, which is key information for decrypting the encrypted data, is added to the counterpart terminal. Then, after the response message is transmitted to the counterpart terminal by the response message transmission means, the encrypted data transmission means transmits the encrypted data to the counterpart terminal after waiting on a predetermined condition. Thus, since the encrypted data is received after the key information is received at the counterpart terminal, the encrypted data can be reliably decrypted with the key information at the counterpart terminal.

  Further, in the first aspect, comprising: key information receiving means for receiving key information from the counterpart terminal; and key information reception determining means for determining whether or not the key information has been received by the key information receiving means, The response message transmission means adds the key information on the local site side when the success message is received by the success message reception means and the key information reception determination means determines that the key information has been received. The response message may be transmitted to the counterpart terminal. As a result, even when key exchange is started from the other party and the corresponding key information is transmitted to the other terminal, the encrypted data is received after the key information is received at the other terminal. The partner terminal can securely decrypt the encrypted data with the key information.

  In the first aspect, the delay time measuring means for measuring the network delay time between the communication terminals, and the arrival time of the response message at the counterpart terminal based on the delay time measured by the delay time measuring means. And the encrypted data transmission means waits until the arrival time estimated by the arrival time estimation means elapses, and the encrypted data when the arrival time elapses. May be transmitted. That is, based on the delay time measured by the delay time measuring means, the arrival time estimating means estimates the arrival time of the response message at the partner terminal. The encrypted data transmission unit waits until the arrival time estimated by the arrival time estimation unit elapses, and transmits the encrypted data when the arrival time elapses. As a result, the arrival time when the key information is transmitted to the partner terminal can be estimated, and after the arrival time has elapsed, the encrypted data is transmitted to the partner terminal so that the key information is received. You can receive encrypted data later. Therefore, the partner terminal can reliably decrypt the encrypted data with the key information.

  In the first aspect, the data processing device further comprises encrypted data receiving means for receiving the encrypted data transmitted from the counterpart terminal, wherein the encrypted data receiving means is configured such that the encrypted data receiving means is the counterpart terminal. It is possible to wait until the encrypted data transmitted from the mobile station is received, and when the encrypted data is received, the data encrypted on the local site side may be transmitted to the counterpart terminal. Encrypted data receiving means receives the encrypted data transmitted from the counterpart terminal. Then, the encrypted data transmitting means waits until the encrypted data receiving means receives the encrypted data transmitted from the counterpart terminal, and when the encrypted data is received, the encrypted data is encrypted at the local site side. Send data to the partner terminal. That is, since the key information has already been transmitted before the data is transmitted from the counterpart terminal, when the data transmitted from the counterpart terminal is received, the key information has already reached the counterpart terminal. Therefore, it waits until the encrypted data transmitted from the partner terminal is received. When the encrypted data is received, the partner terminal transmits the encrypted data to the partner terminal. The encrypted data can be received after the key information is received. Therefore, the partner terminal can reliably decrypt the encrypted data with the key information.

  The communication control method of the communication terminal device according to the second aspect of the present invention is a function that is used in a system using SIP (Session Initiation Protocol) and transmits / receives encrypted data to / from a partner terminal via a network. A communication start request message transmission step of transmitting a communication start request message to the counterpart terminal in order to establish a session with the counterpart terminal; and A success message receiving step that receives a success message that is output from the counterpart terminal that has received the start message and notifies that a communication start request has been accepted, and decrypts the encrypted data when the success message is received A response message with key information, which is key information for A response message transmission step to be transmitted to the terminal, and after the response message is transmitted to the counterpart terminal in the response message transmission step, the encrypted data is transmitted to the counterpart terminal after waiting on a predetermined condition And an encrypted data transmission step.

  The communication control method of the communication terminal device according to the second aspect is used in a system using SIP (Session Initiation Protocol), and transmits / receives encrypted data to / from a partner terminal via a network. First, in a communication start request message transmission step, a communication start request message is transmitted to the counterpart terminal in order to establish a session with the counterpart terminal. Next, in a success message receiving step, a success message is received that is output from the counterpart terminal that has received the communication start message and notifies that the communication start request has been accepted. Further, when the success message is received, in the response message transmission step, a response message to which key information that is key information for decrypting the encrypted data is added is transmitted to the counterpart terminal. Then, after the response message is transmitted to the counterpart terminal, in the encrypted data transmission step, after waiting on a predetermined condition, the encrypted data is transmitted to the counterpart terminal. Thus, since the encrypted data is received after the key information is received at the counterpart terminal, the encrypted data can be reliably decrypted with the key information at the counterpart terminal.

  A communication control program according to a third aspect of the present invention is characterized by causing a computer to function as various processing means of a communication terminal device according to any one of claims 1 to 4.

  Since the communication control program according to the third aspect causes the computer to function as various processing means of the communication terminal device according to any one of claims 1 to 4, the effect according to any one of claims 1 to 4 is obtained. Can do.

1 is a system diagram showing a configuration of a conference system 1. FIG. It is the sequence figure (when key exchange was started from conference terminal 3) which showed the flow of communication in conference terminal 3 and conference terminal 4 in time series. It is a block diagram which shows the electrical structure of the conference terminals 3 and 4. FIG. 3 is a block diagram showing various storage areas of a RAM 43. FIG. It is a flowchart of the data transmission start process by CPU41. It is the sequence figure (when key exchange was started from conference terminal 4) which showed the flow of communication with conference terminal 3 and conference terminal 4 in time series. It is a flowchart of the 1st modification of the data transmission start process by CPU41. It is a flowchart of the 2nd modification of the data transmission start process by CPU41. It is the sequence figure (when key exchange was started from conference terminal 4) which showed the flow of communication with conference terminal 3 and conference terminal 4 in the 2nd modification in time series.

  Hereinafter, conference terminals 3 and 4 according to an embodiment of the present invention will be described with reference to the drawings. These drawings are used to explain the technical features that can be adopted by the present invention, and the described devices, terminal configurations, flowcharts of various processes, and the like have particularly specific descriptions. As long as there is not, it is not the meaning limited only to it but a mere explanatory example.

  First, an overview of the conference system 1 including the conference terminals 3 and 4 as constituent elements will be described with reference to FIG. The conference system 1 includes a conference terminal 3 connected to the Internet 2, a conference terminal 4, and a communication control device 5. A remote conference can be performed by transmitting and receiving video data and audio data between the conference terminals 3 and 4 via the Internet 2. In the present embodiment, for convenience of explanation, the conference terminal 3 is described as the local site side, and the conference terminal 4 is described as the partner site side.

  First, the conference terminals 3 and 4 will be described. The conference terminals 3 and 4 have at least a function (IP telephone function) for communicating with other terminals via the Internet 2 and executing a call between terminal owners. SIP (Session Initiation Protocol) is used as a call control protocol for realizing the IP telephone function. As the conference terminals 3 and 4, a stationary PC, a portable terminal, etc. can be used in addition to a dedicated terminal. The conference terminals 3 and 4 are each provided with a camera 52 for photographing the user.

  Identification information for identifying the user is assigned to each of the conference terminals 3 and 4. In SIP, the SIP address corresponds to identification information. The user can make a call with a specific user by designating the SIP address and calling the specific user's call terminal.

  Next, the communication control device 5 will be described. The communication control device 5 functions as a SIP server in SIP. The communication control device 5 centrally manages users, telephone numbers, IP addresses, and the like. The communication control device 5 has at least a proxy function that receives and relays an inquiry (request) from the conference terminals 3 and 4. The communication control device 5 has a register function that accepts registration requests from the conference terminals 3 and 4, a redirect function that examines the destination of the other conference terminal 3 and 4 and tells the inquiry source, and information on the conference terminals 3 and 4 ( A location function for managing the location of the terminal) may be provided.

  Next, the proxy function of the communication control device 5 will be described. The proxy function accepts a call request from the conference terminals 3 and 4 and transfers the packet to the conference terminals 3 and 4 on the other side. Therefore, as an example, a general example of receiving a connection request from the conference terminal 3 and transferring a packet to the conference terminal 4 on the other side will be described with reference to the sequence diagram of FIG.

  First, the conference terminal 3 transmits a signal for requesting the start of a call (hereinafter referred to as a call request “INVITE”) to the communication control device 5 at the timing T1. When the communication control device 5 receives the call request “INVITE”, the communication control device 5 checks the SIP address of the conference terminal 4 of the other party, and responds to the conference terminal 4 that investigated the received call request “INVITE” at the timing T2. Forward. Next, a signal for notifying that the call request “INVITE” is being executed (hereinafter referred to as an execution response “100 Trying”) is transmitted to the conference terminal 3 at the timing T3.

  On the other hand, in the destination conference terminal 4 that has received the call request, a call process is executed, and a signal for notifying a provisional response (hereinafter referred to as provisional response “180 Ringing”) at the timing T4 is communication controlled. It is transmitted to the device 5. When receiving the provisional response “180 Ringing”, the communication control device 5 transfers the provisional response “180 Ringing” to the conference terminal 3 at the timing T5. Further, when the destination conference terminal 4 is off-hooked, a signal for notifying that the communication has succeeded (hereinafter, a success response “200 OK”) is transmitted to the communication control device 5 at the timing T6. .

  When the communication control device 5 receives the success response “200 OK”, the communication control device 5 transfers the success response to the conference terminal 3 at T7 timing. Upon receiving the success response, the conference terminal 3 transmits a signal indicating that the session has been established (hereinafter referred to as an acknowledgment “ACK”) to the communication control device 5 at T8 timing. When receiving the confirmation response “ACK”, the communication control device 5 transfers the confirmation response to the conference terminal 4. When the confirmation response “ACK” is received by the conference terminal 4, video data and audio data communication is started between the conference terminal 3 and the conference terminal 4 (timing T 9 and T 10).

  Next, SDES will be described. In the conference system 1, encrypted communication for transmitting / receiving encrypted video data and audio data is performed between the conference terminals 3 and 4. When performing encrypted communication, it is necessary to exchange key information between clients. In this embodiment, SDES (Session Description Protocol Security Description for Media Streams) is used as a protocol for exchanging key information. SDES is suitable for a system that transmits and receives video data and audio data because encryption and decryption are fast. In SDES, key information for encryption is written in the SDP added to the SIP message. Thereby, key exchange can be performed between clients.

  Next, FIG. 2 shows a case 1 in which key exchange is started from the conference terminal 3 on the local site side and a case 2 in which key exchange is initiated from the conference terminal 4 on the other site in the case of key exchange. This will be described in sequence with reference to the sequence diagram.

Case 1: Example of starting key exchange from the conference terminal 3 at the local site When a call request “INVITE” is made from the conference terminal 3 at the local site at the T1 timing, the SIP message is transmitted from the conference terminal 3 The key information, which is common key information necessary for decrypting the encrypted data to be decrypted, is written. The key information reaches the destination conference terminal 4 at the timing T2 via the communication control device 5 together with the call request “INVITE”. Thereby, the conference terminal 4 can decrypt the encrypted audio / video data transmitted from the conference terminal 3 by using the key information.

  The conference terminal 3 also needs key information necessary for decrypting the encrypted data transmitted from the conference terminal 4. Therefore, the key information is written in the SIP message of the successful response “200 OK” transmitted at the timing T6. The key information reaches the conference terminal 3 at the timing T7 via the communication control device 5 together with the success response “200 OK”. As a result, the conference terminal 3 can subsequently decrypt the encrypted audio / video data transmitted from the conference terminal 4 by using the key information.

Case 2: Example of starting key exchange from the conference terminal 4 that is the partner site Key information is written in the SIP message of the success response “200 OK” at T6 timing, and via the communication control device 5 at T7 timing. To the conference terminal 3. Thereby, the conference terminal 3 can decrypt the encrypted audio / video data transmitted from the conference terminal 4 by using the key information. The conference terminal 4 also requires key information necessary for decrypting the encrypted data transmitted from the conference terminal 3. Therefore, the key information is written in the SIP message of the acknowledgment “ACK” transmitted at the timing T8. The key information reaches the conference terminal 4 through the communication control device 5 together with the confirmation response “ACK”. Thereby, the conference terminal 4 can subsequently decrypt the encrypted audio / video data transmitted from the conference terminal 3 by using the key information.

  Next, the electrical configuration of the conference terminal 3 will be described with reference to FIG. The conference terminal 3 includes a CPU 41 that executes communication control with other terminals, a ROM 42 that stores various programs executed by the CPU 41, and a RAM 43 that temporarily stores key information, flag information, timer information, counter information, and the like. And a flash memory 44 in which image data to be displayed on the display 53, sound source data to be output from the speaker 47, and the like are stored. The CPU 41, the ROM 42, the RAM 43, and the flash memory 44 are electrically connected to each other. The CPU 41 can access various storage areas of the ROM 42, the RAM 43, and the flash memory 44.

  The conference terminal 3 includes a communication module 45 for connecting to the Internet 2. The CPU 41 and the communication module 45 are electrically connected. The CPU 41 can transmit desired data to the Internet 2. Further, the CPU 41 can recognize data received from the Internet 2. For example, a network card can be used as the communication module 45.

  The conference terminal 3 includes a camera drive circuit 46 that drives a camera 52 for projecting a video of the local site, a speaker 47 that outputs the audio of another site, and a microphone 48 that inputs the audio of the local site. The CPU 41, the camera drive circuit 46, the speaker 47, and the microphone 48 are electrically connected to each other. The CPU 41 can output desired sound from the speaker 47. The CPU 41 can recognize voice input via the microphone 48.

  The conference terminal 3 includes a display 53 and a display driver 49 that can display an image on the display 53. The CPU 41 and the display driver 49 are electrically connected. The display driver 49 and the display 53 are electrically connected. The CPU 41 can display the video data transmitted from the destination conference terminal 4 on the display 53.

  The conference terminal 3 includes a keyboard 54 and an input driver 50 that can detect information input by the user via the keyboard 54. The CPU 41 and the input driver 50 are electrically connected. The input driver 50 and the keyboard 54 are electrically connected. The CPU 41 can recognize information input via the keyboard 54.

  The conference terminal 3 includes a CD-ROM drive 55 that can read information stored in the CD-ROM 30. The CPU 21 and the CD-ROM drive 55 are electrically connected. In the CD-ROM 30, for example, a program necessary for driving the CPU 21, a data transmission start program, and the like are stored. The CPU 21 can recognize information stored in the CD-ROM 30.

  Next, various storage areas of the RAM 43 will be described with reference to FIG. The RAM 43 stores a reception data storage area 431 for storing video data and audio data transmitted from other conference terminals, and a communication time storage for storing the time taken for communication with the other conference terminal. An area 432, a key information storage area 433 for storing key information transmitted from the counterpart terminal, and the like are provided.

  Next, data transmission start processing by the CPU 41 will be described with reference to the flowchart of FIG. 5 and the sequence diagram of FIG. First, a call request “INVITE” is transmitted at timing T21 (S11). Then, at that timing, a timer (not shown) is turned on to start measuring the communication time (S12).

  On the other hand, when the communication control device 5 receives the call request “INVITE”, the communication control device 5 checks the SIP address of the destination conference terminal 4, etc., and at the timing T22, the communication control device 5 Forward. Next, an execution response “100 Trying” is transmitted to the conference terminal 3 at T23 timing. Then, the destination conference terminal 4 that has received the call request executes a call process and transmits a provisional response “180 Ringing” to the communication control device 5 at the timing T24. When receiving the provisional response “180 Ringing”, the communication control device 5 transfers the provisional response “180 Ringing” to the conference terminal 4 at T25 timing.

  Then, the conference terminal 3 determines whether or not a provisional response “180 Ringing” has been received (S13). If not received yet (S13: NO), the process returns to S13 and is repeated until received. When the provisional response “180 Ringing” is received (S13: YES), the timer is turned off, the communication time measured by the timer, that is, the call request “INVITE” is transmitted to the partner, and then transmitted from the partner. The communication time until the provisional response “180 Ringing” is received is stored in the communication time storage area 432 of the RAM 43 (S14).

  On the other hand, when the destination conference terminal 4 is off-hooked, a success response “200 OK” is transmitted to the communication control device 5 at T26 timing. When the communication control device 5 receives the success response “200 OK”, the communication control device 5 transfers the success response to the conference terminal 3 at the timing T27.

  Then, the conference terminal 3 determines whether or not the success response “200 OK” has been received (S15). If not received yet (S15: NO), the process returns to S15 and is repeated until received. When the success response “200 OK” is received at the timing T27 (S15: YES), it is determined whether or not key information is attached to the SIP message of the success response (S16). When the key information is not given (S16: NO), since encrypted communication is not performed with the destination conference terminal 4, only the confirmation response “ACK” is transmitted to the communication control device 5 at T28 timing. (S17).

  When the communication control device 5 receives the confirmation response “ACK”, it transfers the confirmation response to the conference terminal 4. Then, the conference terminal 4 receives the confirmation response “ACK”. Next, encrypted data transmission for transmitting the video data captured by the camera 52 and the audio data input to the microphone 48 to the destination conference terminal 4 is started (S20). Further, the encrypted data transmission is also started from the conference terminal 4 to the conference terminal 3. In this case, video data and audio data are transmitted and received without being encrypted between the conference terminal 3 and the conference terminal 4.

  On the other hand, if the success response “200 OK” is received (S15: YES) and the key information is added to the SIP message of the success response (S16: YES), the key is received from the conference terminal 4 of the other party. Since the start of the exchange is requested, the key information is written in the SIP message of the confirmation response “ACK” at T28 timing, and the confirmation response “ACK” with the key information is transmitted (S18). The key information reaches the conference terminal 4 through the communication control device 5 together with the confirmation response “ACK”. In the conference terminal 4, the key information given to the confirmation response “ACK” is stored in the key information storage area 433 (see FIG. 4) of the RAM 43.

  Next, it is determined whether or not an arrival time that is ½ of the communication time stored in the communication time storage area 432 of the RAM 43 has elapsed since the confirmation response “ACK” to which the key information was added was transmitted. (S19). As described above, the communication time is the time from when the call request “INVITE” is transmitted to the other party until the provisional response “180 Ringing” transmitted from the other party is received. Therefore, ½ of the time from when “INVITE” is sent to the other party until “180 Ringing” returns can be regarded as the arrival time. Note that it is estimated that this arrival time is delayed by the amount that has passed through the communication control device 5.

  Therefore, when the arrival time has not yet elapsed (S19: NO), the process returns to S19 and is repeated until the arrival time has elapsed. If the arrival time has elapsed (S19: YES), since the confirmation response “ACK” to which the key information has been added has already reached the destination conference terminal 4, encryption is performed at the timing T29. The video data and audio data thus transmitted are transmitted to the conference terminal 4 (S20). Furthermore, transmission of encrypted data is also started from the conference terminal 4 to the conference terminal 3 at the timing T30.

  The destination conference terminal 4 receives the encrypted video data and audio data and temporarily stores them in the received data storage area 431 of the RAM 43. That is, it is possible to prevent the encrypted audio / video data from reaching the conference terminal 4 before the key information regardless of the network status of the Internet 2. Then, the conference terminal 4 can decrypt all the encrypted video data and audio data stored in the RAM 43 from the beginning with the key information stored in the RAM 43. Thereby, it is possible to have a good conversation between the conference terminal 3 and the conference terminal 4 via video and audio while maintaining security.

  As described above, in the conference terminal 3 of the conference system 1 according to the present embodiment, in order to perform encrypted communication, when key exchange is started from the conference terminal 4 of the other party, “INVITE” is set to the other party. One half of the communication time from when sending to the conference terminal 4 until “180 Ringing” returns is regarded as the arrival time until data arrives from the conference terminal 3 to the conference terminal 4. Then, after the key information is attached to “ACK” and transmitted to the conference terminal 4, the encrypted data is not transmitted to the conference terminal 4 immediately, but is transmitted after the arrival time has elapsed. Accordingly, it is possible to prevent the encrypted audio / video data from reaching the conference terminal 4 before the key information regardless of the network status of the Internet 2. Thereby, it is possible to have a good conversation between the conference terminal 3 and the conference terminal 4 via video and audio while maintaining security.

  In the conference system 1, a conference is performed by transmitting and receiving video data using an I picture and a P picture. Even when an I picture is included in a portion that cannot be decoded, the key information is received before the I picture. Therefore, it is possible to reliably decode a P picture that is a video with reference to the I picture. Thereby, the video can be reproduced satisfactorily.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above embodiment, when key exchange is started from the destination conference terminal 4, the communication time from when “INVITE” is sent to the destination conference terminal 4 until “180 Ringing” returns is measured. Then, 1/2 is regarded as the arrival time until data arrives from the conference terminal 3 to the conference terminal 4, and the key information is attached to “ACK” and transmitted to the conference terminal 4. Is sending from.

  Separately from this, for example, a ping command may be used to measure a delay time required for communication between the conference terminal 3 and the conference terminal 4 and to wait for transmission of the encrypted data by the delay time. In addition, after the key information is assigned to “ACK” and transmitted to the conference terminal 4, the transmission of the encrypted data is made to wait until the video data and audio data transmitted from the conference terminal 4 is received. Also good. Therefore, the former will be described in the following order as the first modification and the latter as the second modification.

First Modification A data transmission start process of the CPU 41 using the delay time measured using the ping command will be described with reference to the sequence diagram of FIG. 6 and the flowchart of FIG. First, a call request “INVITE” is transmitted at T21 timing (S31). Next, a delay time detection process is executed (S32). In the delay time detection process, a ping command is used.

  Ping is a command for issuing an IP packet to a host whose network communication is to be confirmed, and confirming whether the packet has arrived correctly and a response is made. First, the host name or IP address of the conference terminal 4 whose communication is to be confirmed is specified. For example, packet transmission / reception is performed a predetermined number of times (for example, four times), and the status of each time is detected. As the status, a data size (bytes) of the received ICMP packet and a delay time (millisecond) from transmission of the packet to reception are detected. Then, an average value of the predetermined number of statuses is calculated as a trial result. Then, the average value of the calculated delay times is stored in the RAM 43 (S33).

  Next, it is determined whether or not a provisional response “180 Ringing” has been received (S34). If it has not been received yet (S34: NO), the process returns to S34 and is repeated until it is received. When the provisional response “180 Ringing” is received (S34: YES), it is further determined whether or not the success response “200 OK” is received (S35). If not received yet (S35: NO), the process returns to S35 and is repeated until received. When the success response “200 OK” is received (S35: YES), it is determined whether or not key information is attached to the SIP message of the success response (S36). When the key information is not given (S36: NO), since encrypted communication is not performed with the destination conference terminal 4, only the confirmation response “ACK” is transmitted to the communication control device 5 at T28 timing. (S37).

  When the communication control device 5 receives the confirmation response “ACK”, it transfers the confirmation response to the conference terminal 4. Then, the conference terminal 4 receives the confirmation response “ACK”. Then, data transmission is started in which the video data photographed by the camera 52 and the audio data input to the microphone 48 are transmitted to the destination conference terminal 4 (S40). In this case, video data and audio data are transmitted and received without being encrypted between the conference terminal 3 and the conference terminal 4.

  On the other hand, when the success response “200 OK” is received (S35: YES) and the key information is added to the SIP message of the success response (S36: YES), the key is received from the conference terminal 4 of the other party. Since the start of the exchange is requested, the key information is written in the SIP message of the confirmation response “ACK” at the timing T28, and the confirmation response “ACK” with the key information is transmitted (S38). The key information reaches the conference terminal 4 through the communication control device 5 together with the confirmation response “ACK”. In the conference terminal 4, the key information given to the confirmation response “ACK” is stored in the key information storage area 433 (see FIG. 4) of the RAM 43.

  Next, it is determined whether or not the delay time stored in the RAM 43 has elapsed since the confirmation response “ACK” with the key information is transmitted (S39). If the delay time has not yet elapsed (S39: NO), the process returns to S39 and is repeated until the arrival time elapses. If the delay time has elapsed (S39: YES), since the confirmation response “ACK” to which the key information has been added has already reached the destination conference terminal 4, encryption is performed at the timing T29. The video data and audio data thus transmitted are transmitted to the conference terminal 4 (S40).

  The destination conference terminal 4 receives the encrypted video data and audio data and temporarily stores them in the reception data storage area 431 of the RAM 43. That is, it is possible to prevent the encrypted audio / video data from reaching the conference terminal 4 before the key information regardless of the network status of the Internet 2. Then, the conference terminal 4 can decrypt all the encrypted video data and audio data stored in the RAM 43 from the beginning with the key information stored in the RAM 43. Thereby, also in a 1st modification, it is possible to have a good conversation between the conference terminal 3 and the conference terminal 4 via video and audio while maintaining security.

Second Modified Example Regarding the data transmission start processing of the CPU 41 that waits for data transmission until receiving video data and audio data transmitted from the conference terminal 4 of the other party, the flowchart of FIG. 8 and the sequence diagram of FIG. The description will be given with reference. First, a call request “INVITE” is transmitted at timing T31 (S51).

  Next, it is determined whether or not a provisional response “180 Ringing” has been received (S52). If not received yet (S52: NO), the process returns to S52 and is repeated until received. When the provisional response “180 Ringing” is received at the timing T32 (S52: YES), it is further determined whether or not the success response “200 OK” is received (S53). If not received yet (S53: NO), the process returns to S53 and is repeated until received. When the success response “200 OK” is received at the timing T33 (S53: YES), it is determined whether or not key information is attached to the SIP message of the success response (S54). When the key information is not given (S54: NO), since encrypted communication is not performed with the conference terminal 4 of the other party, only the confirmation response “ACK” is transmitted to the communication control device 5 at T34 timing. (S37).

  When the communication control device 5 receives the confirmation response “ACK”, it transfers the confirmation response to the conference terminal 4. When the confirmation response “ACK” is received by the conference terminal 4, since encrypted communication is not performed, the video data captured by the camera 52 and the audio data input to the microphone 48 are used as the conference of the other party. Data transmission to be transmitted to the terminal 4 is started (S58). In this case, video data and audio data are transmitted and received without being encrypted between the conference terminal 3 and the conference terminal 4.

  On the other hand, if the success response “200 OK” is received (S53: YES) and the key information is attached to the SIP message of the success response (S54: YES), the key is received from the conference terminal 4 of the other party. Since the start of the exchange is requested, the key information is written in the SIP message of the confirmation response “ACK” at T34 timing, and the confirmation response “ACK” with the key information is transmitted (S56). The key information reaches the conference terminal 4 through the communication control device 5 together with the confirmation response “ACK”. In the conference terminal 4, the key information given to the confirmation response “ACK” is stored in the key information storage area 433 (see FIG. 4) of the RAM 43.

  Next, it is determined whether the video data and audio data transmitted from the destination conference terminal 4 have been received (S57). If it has not been received yet, the process returns to S57 and is repeated. If the video data and audio data of the other party are received at the timing T35 (S57: YES), the key information transmitted together with “ACK” from the conference terminal 3 should have already arrived at the conference terminal 4. . Therefore, transmission of the encrypted video data and audio data at the local site is started at T36 timing (S58).

  Accordingly, it is possible to prevent the encrypted audio / video data from reaching the conference terminal 4 before the key information regardless of the network status of the Internet 2. Then, the conference terminal 4 can decrypt all the encrypted video data and audio data stored in the RAM 43 from the beginning with the key information stored in the RAM 43. Thereby, also in a 2nd modification, it can talk favorably between a conference terminal 3 and the conference terminal 4 via an image | video and an audio | voice, maintaining security.

  Moreover, in the said embodiment, although the communication control apparatus 5 is provided as a SIP server, since the conference terminals 3 and 4 can talk directly, the communication control apparatus 5 does not need to be provided.

DESCRIPTION OF SYMBOLS 1 Conference system 2 Internet 3 Conference terminal 4 Conference terminal 5 Communication control apparatus 41 CPU
43 RAM
47 Speaker 48 Microphone 52 Camera 53 Display 431 Received data storage area 432 Communication time storage area 433 Key information storage area

Claims (6)

A communication terminal device used in a system using SIP (Session Initiation Protocol) and having a function of transmitting / receiving encrypted data to / from a partner terminal via a network,
A communication start request message transmitting means for transmitting a communication start request message to the counterpart terminal in order to establish a session with the counterpart terminal;
Success message receiving means for receiving a success message that is output from the counterpart terminal that has received the communication start request message and notifies that the communication start request has been accepted;
A response message transmitting means for transmitting a response message with key information, which is key information for decrypting the encrypted data, to the counterpart terminal when the success message is received;
After the response message is transmitted to the counterpart terminal by the response message transmission means, the encrypted message transmission means transmits the encrypted data to the counterpart terminal after waiting on a predetermined condition. A communication terminal device. Key information receiving means for receiving key information from the counterpart terminal;
Key information reception determining means for determining whether the key information is received by the key information receiving means,
The response message transmission means adds the key information on the local site side when the success message is received by the success message reception means and the key information reception determination means determines that the key information has been received. The communication terminal apparatus according to claim 1, wherein the response message transmitted is transmitted to the counterpart terminal. A delay time measuring means for measuring a network delay time between communication terminals;
Based on the delay time measured by the delay time measuring means, the arrival time estimating means for estimating the arrival time of the response message at the counterpart terminal,
The encrypted data transmission means includes:
The communication terminal according to claim 1 or 2, wherein the communication terminal waits until the arrival time estimated by the arrival time estimation means elapses, and transmits the encrypted data when the arrival time elapses. apparatus. Comprising encrypted data receiving means for receiving the encrypted data transmitted from the counterpart terminal;
The encrypted data transmitting means waits until the encrypted data receiving means receives the encrypted data transmitted from the counterpart terminal, and when receiving the encrypted data, the encrypted data transmitting means The communication terminal apparatus according to claim 1, wherein the converted data is transmitted to the counterpart terminal. A communication control method for a communication terminal device used in a system using SIP (Session Initiation Protocol) and having a function of transmitting / receiving encrypted data to / from a partner terminal via a network,
A communication start request message transmission step for transmitting a communication start request message to the counterpart terminal in order to establish a session with the counterpart terminal;
Success message reception step of receiving a success message that is output from the counterpart terminal that has received the communication start message and notifies that a communication start request has been accepted
A response message sending step for sending a response message with key information, which is key information for decrypting the encrypted data, to the counterpart terminal when the success message is received;
After the response message is transmitted to the counterpart terminal in the response message transmission step, the encrypted message transmission step of transmitting the encrypted data to the counterpart terminal after waiting on a predetermined condition A communication control method for a communication terminal device.   A communication control program for causing a computer to function as various processing means of the communication terminal device according to any one of claims 1 to 4.

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