JP2019075733A - Communication system, communication device, and method thereof - Google Patents

Abstract

To provide a communication system that can perform key exchange securely with little computational effort.SOLUTION: A communication system includes a first communication device 1 and a second communication device. The first communication device 1 includes a first common key generation unit 101 that generates a first common key, a data encryption unit 102 that encrypts data using the first common key to generate first encrypted data, a second common key generation unit 103 that generates a second common key from a part of the first encrypted data, a common key encryption unit 104 that encrypts the first common key by using the second common key to generate a third common key, a combining unit 105 that combines the first encrypted data and the third common key to generate second encrypted data, and transmission means 106 that transmits the second encrypted data to the second communication device.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication system, a communication device, and a method thereof, and more particularly to a communication system, a communication device, and a method, which exchange a common key between communication terminals.

  In a communication system, a technique for encrypting communication data is used to prevent eavesdropping, tampering, etc. of the communication data. A common key cryptosystem is known as a technique for this encryption. The common key encryption scheme is a scheme in which encryption and decryption are performed using a common key as a common encryption key between the transmitting terminal and the receiving terminal.

  In the common key encryption method, in general, the transmitting terminal and the receiving terminal hold each other a common key in advance, and continue to use the held common key. Therefore, the solution of the vulnerability that the common key is easily guessed by the third party has been an issue. As a method for solving this problem, there is a method of updating the common key for each session using RSA (registered trademark) or Diffie-Hellman key exchange. As an example of this method, Patent Document 1 discloses a technique of updating a common key using a public key encryption method such as RSA.

JP, 2014-175970, A

  However, in the technology disclosed in Patent Document 1, the common key can be shared without leaking information to a third party by using the concept of public key encryption, but the amount of calculation required for processing is There was a problem that there were many. Therefore, the technology disclosed in Patent Document 1 does not have sufficient CPU (Central Processing Unit) performance and memory capacity, such as IoT (Internet of Things) devices, and is not suitable for use in terminals with high power consumption demand. Was a problem.

  The present invention has been made to solve such problems, and it is an object of the present invention to provide a communication system, a communication device, and a method thereof that can securely perform key exchange with a small amount of calculation.

  A communication system according to a first aspect of the present invention includes a first communication device and a second communication device, and the first communication device generates a first common key. Means, data encryption means for encrypting data using said first common key to generate first encrypted data, and generating a second common key from a portion of said first encrypted data Common key encryption means for encrypting the first common key using the second common key to generate a third common key, and the first encryption And combining means for combining data and the third common key to generate second encrypted data, and transmitting means for transmitting the second encrypted data to the second communication device. The second communication device, receiving means for receiving the second encrypted data from the first communication device; A division unit configured to divide second encrypted data into the first encrypted data and the third common key; and generating the second common key from a part of the first encrypted data Using two common key generation means, common key decryption means for decoding the first common key from the third common key using the second common key, and the first common key using the first common key Data decryption means for decrypting said data from one piece of encrypted data.

  A communication apparatus according to a second aspect of the present invention encrypts data by using a first common key generation unit that generates a first common key, and the first common key to generate first encrypted data. Data encryption means for generating a second common key generation means for generating a second common key from a part of the first encrypted data, and the first common key using the second common key. Common key encryption means for encrypting a common key to generate a third common key, and combining the first encrypted data and the third common key to generate second encrypted data And transmission means for transmitting the second encrypted data.

  A communication apparatus according to a third aspect of the present invention divides the second encrypted data into first encrypted data and a third common key, and receiving means for receiving the second encrypted data. A division unit, a second common key generation unit for generating a second common key from a part of the first encrypted data, and a third common key using the second common key; A common key decryption unit that decrypts the common key, and a data decryption unit that decrypts data from the first encrypted data using the first common key.

  A method according to a fourth aspect of the present invention is a method of a communication system comprising a first communication device and a second communication device, wherein the first communication device generates a first common key. Encrypting the data using the first common key to generate first encrypted data, generating a second common key from a portion of the first encrypted data, and generating the second common key A key is used to encrypt the first common key to generate a third common key, and the first encrypted data and the third common key are combined to generate second encrypted data. Transmitting the second encrypted data to the second communication device, the second communication device receiving the second encrypted data from the first communication device, Dividing the second encrypted data into the first encrypted data and the third common key, and dividing the second encrypted data into the first encrypted data; The second common key from the second common key and decrypting the first common key from the third common key using the second common key, and the first common key using the first common key. And decrypting the data from the encrypted data.

  A method according to a fifth aspect of the present invention is a method of a communication apparatus, which generates a first common key, encrypts data using the first common key, and generates first encrypted data. Generating a second common key from part of the first encrypted data, and encrypting the first common key using the second common key to generate a third common key; And combining the first encrypted data and the third common key to generate second encrypted data, and transmitting the second encrypted data.

  A method according to a sixth aspect of the present invention is a method of a communication device, comprising: receiving second encrypted data, the second encrypted data being the first encrypted data and the third common key To generate a second common key from a portion of the first encrypted data, and decrypting the first common key from the third common key using the second common key, Decrypting the data from the first encrypted data using the first common key.

  According to the present invention, it is possible to provide a communication system, a communication device, and a method thereof that can securely exchange keys with a small amount of calculation.

FIG. 1 is a block diagram showing an example of configuration of a communication system according to a first exemplary embodiment. FIG. 2 is a block diagram showing an example of configuration of a first communication device according to Embodiment 1. 5 is a flowchart illustrating an example of processing of the first communication device according to the first embodiment. FIG. 7 is a diagram for explaining an example of processing of the first communication device according to the first embodiment; FIG. 6 is a block diagram showing an example of configuration of a second communication device according to Embodiment 1. 5 is a flowchart illustrating an example of processing of a second communication device according to the first embodiment. FIG. 7 is a diagram for explaining an example of processing of a second communication device according to the first embodiment; FIG. 18 is a diagram for describing an example of a process of generating a second common key according to the second embodiment. FIG. 18 is a diagram for describing an example of a process of generating second encrypted data according to the third embodiment. FIG. 18 is a diagram for describing an example of a division process of second encrypted data according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding elements are denoted by the same reference numerals, and for the sake of clarity of the description, redundant description will be omitted as necessary.

Embodiment 1
First, a configuration example of the communication system 10 according to the first embodiment of the present invention will be described using the block diagram of FIG. The communication system 10 includes a communication device 1 and a communication device 2. The communication device 1 is also referred to as a first communication device. The communication device 2 is also referred to as a second communication device.

  The communication device 1 and the communication device 2 are communicably connected via a communication line. The communication line between the communication device 1 and the communication device 2 may be a wireless communication line or a wired communication line. Also, a part may be wireless and the other part may be a wired communication line.

  Subsequently, a configuration example of the communication device 1 according to the first embodiment of the present invention will be described using the block diagram of FIG. The communication device 1 includes a first common key generation unit 101, a data encryption unit 102, a second common key generation unit 103, a common key encryption unit 104, a combination unit 105, and a transmission unit 106. Is equipped.

  The first common key generation unit 101 is a functional unit that generates a first common key. The first common key generation unit 101 generates a first common key, for example, using random data such as time information. The first common key generation unit 101 outputs the generated first common key to the data encryption unit 102 and the common key encryption unit 104.

  The data encryption unit 102 receives the first common key from the first common key generation unit 101. Also, the data encryption unit 102 encrypts plaintext data using the first common key to generate first encrypted data. The data encryption unit 102 uses an encryption method generally used in common key encryption, such as AES (Advanced Encryption Standard). Then, the data encryption unit 102 outputs the generated first encrypted data to the second common key generation unit 103 and the combination unit 105.

  The second common key generation unit 103 receives the first encrypted data from the data encryption unit 102. Further, the second common key generation unit 103 generates a second common key from a part of the first encrypted data.

  For example, the second common key generation unit 103 extracts partial data of a predetermined bit length necessary as a common key from the end of the first encrypted data, and uses the extracted partial data as a second common key. Thus, the second common key is generated. Then, second common key generation unit 103 outputs the generated second common key to common key encryption unit 104.

  The common key encryption unit 104 receives the first common key from the first common key generation unit 101. Also, the common key encryption unit 104 receives the second common key from the second common key generation unit 103. Also, the common key encryption unit 104 encrypts the first common key using the second common key to generate a third common key. That is, the common key encryption unit 104 encrypts the first common key to generate a third common key, using the second common key as a key of the common key cryptosystem. Then, the common key encryption unit 104 outputs the generated third common key to the combination unit 105.

  The combining unit 105 receives the first encrypted data from the data encryption unit 102. Also, the combining unit 105 receives the third common key from the common key encryption unit 104. In addition, the combining unit 105 combines the first encrypted data and the third common key to generate second encrypted data which is one transmission data.

  Specifically, the combining unit 105 combines the first encrypted data and the third common key according to a predetermined scheme to generate second encrypted data. The predetermined method is, for example, combining the third common key with the end of the first encrypted data. Then, combining section 105 outputs the generated second encrypted data to transmitting section 106.

  The transmitting unit 106 receives the second encrypted data from the combining unit 105. Then, the transmission unit 106 transmits the second encrypted data to the communication device 2 via the communication line.

  Then, the process example of the communication apparatus 1 concerning Embodiment 1 of this invention is demonstrated using FIG.3 and FIG.4. Note that, in FIG. 3 and FIG. 4, steps with the same numbers indicate the same processing.

  First, the communication device 1 generates a first common key by using the random data by the first common key generation unit 101 (step S101).

  Next, the communication device 1 causes the data encryption unit 102 to encrypt data using the first common key to generate first encrypted data (step S102).

  Next, the communication device 1 generates a second common key from a part of the first encrypted data by the second common key generation unit 103 (step S103). FIG. 4 illustrates an example in which partial data of a predetermined bit length is extracted from the end of the first encrypted data, and the extracted partial data is used as a second common key.

  Next, the communication device 1 causes the common key encryption unit 104 to encrypt the first common key using the second common key to generate a third common key (step S104).

  Next, the communication device 1 causes the combining unit 105 to combine the first encrypted data and the third common key to generate second encrypted data (step S105). Note that FIG. 4 shows an example in which the third common key is combined with the end of the first encrypted data to generate the second encrypted data.

  Next, the communication device 1 causes the transmitting unit 106 to transmit the second encrypted data to the communication device 2 (step S106).

  Note that the communication device 1 performs the processing from step S101 to step S106 for each data transmission. That is, a random value is used for each data transmission as the first common key and the second common key.

  Subsequently, a configuration example of the communication device 2 according to the first embodiment of the present invention will be described using the block diagram of FIG. The communication device 2 includes a reception unit 201, a division unit 202, a second common key generation unit 203, a common key decryption unit 204, and a data decryption unit 205.

  The receiving unit 201 receives the second encrypted data from the communication device 1. Then, the receiving unit 201 outputs the received second encrypted data to the dividing unit 202.

  The dividing unit 202 receives the second encrypted data from the receiving unit 201. Further, the dividing unit 202 divides the second encrypted data into the first encrypted data and the third common key.

  Specifically, the dividing unit 202 divides the second encrypted data into the first encrypted data and the third common key according to the scheme combined by the combining unit 105 of the communication device 1. Note that the method combined by the combining unit 105 of the communication device 1 is, for example, a predetermined method such as combining the third common key with the end of the first encrypted data. In this case, in the division unit 202, the end of the first encrypted data is combined with the third common key, and the bit length of the third common key is set in advance. The dividing unit 202 extracts partial data corresponding to the bit length of the third common key from the end of the second encrypted data based on these pieces of information, and uses the remaining data as the first encrypted data. And dividing the second encrypted data into the first encrypted data and the third common key.

  Then, division unit 202 outputs the first encrypted data to second common key generation unit 203 and data decryption unit 205. The dividing unit 202 also outputs the third common key to the common key decryption unit 204.

  The second common key generation unit 203 receives the first encrypted data from the division unit 202. Further, the second common key generation unit 203 generates a second common key from a part of the first encrypted data. The second common key generation unit 203 has the same function as the second common key generation unit 103 of the communication device 1.

  Specifically, the second common key generation unit 203 generates a second common key from a part of the first encrypted data by the same method as the second common key generation unit 103 of the communication device 1. . That is, when the second common key generation unit 103 extracts partial data of a predetermined bit length from the end of the first encrypted data and uses the partial data as the second common key, The common key generation unit 203 generates the second common key using the same method as this. Thus, the second common key generation unit 203 can generate the same second common key as the second common key generated by the second common key generation unit 103.

  Then, the second common key generation unit 203 outputs the generated second common key to the common key decryption unit 204.

  The common key decryption unit 204 receives the third common key from the division unit 202. Also, the common key decryption unit 204 receives the second common key from the second common key generation unit 203. Also, the common key decryption unit 204 decrypts the first common key from the third common key using the second common key. That is, the common key decryption unit 204 decrypts the first common key from the third common key using the second common key as a key of the common key cryptosystem. Then, the common key decryption unit 204 outputs the decrypted first common key to the data decryption unit 205.

  The data decryption unit 205 receives the first encrypted data from the division unit 202. Also, the data decryption unit 205 receives the first common key from the common key decryption unit 204. Then, the data decryption unit 205 decrypts the data from the first encrypted data using the first common key.

  Then, the process example of the communication apparatus 2 concerning Embodiment 1 of this invention is demonstrated using FIG.6 and FIG.7. In FIGS. 6 and 7, steps with the same numbers indicate the same processing.

  First, the communication device 2 causes the receiving unit 201 to receive the second encrypted data from the communication device 1 (step S201).

  Next, the communication device 2 causes the dividing unit 202 to divide the second encrypted data into the first encrypted data and the third common key (step S202).

  Next, the communication device 2 generates a second common key from a part of the first encrypted data by the second common key generation unit 203 (step S203).

  Next, the communication apparatus 2 causes the common key decryption unit 204 to decrypt the first common key from the third common key using the second common key (step S204).

  Next, the communication device 2 causes the data decryption unit 205 to decrypt data from the first encrypted data using the first common key (step S205).

  The communication device 2 performs the process of steps S201 to S205 every time data is received. That is, a random value is used for each data reception as the first common key and the second common key.

  As described above, the communication system 10 according to the first embodiment of the present invention includes the communication device 1 and the communication device 2. Further, the communication device 1 and the communication device 2 according to the first embodiment are each configured to include a second common key generation unit that generates a second common key from a part of the first encrypted data. That is, in the communication system 10 according to the first embodiment, the communication device 1 and the communication device 2 can generate the same second common key using the same predetermined method. The communication device 1 and the communication device 2 can use the second common key generated from a part of the first encrypted data as the key of the common key encryption system.

  Further, the communication device 1 according to the first embodiment encrypts the first common key using the second common key to generate a third common key, and the first encrypted data and the third encrypted key are generated. The common key is combined to generate second encrypted data. Further, the communication device 2 according to the first embodiment divides the second encrypted data into the first encrypted data and the third common key, and uses the second common key to generate the third common. The configuration is such that the first common key is decrypted from the key. Therefore, the communication device 2 according to the first embodiment can acquire the first common key generated by the communication device 1 from the second encrypted data received from the communication device 1.

  On the other hand, the configuration of the first encrypted data and the third common key in the second encrypted data is unknown to a third party who attempts to eavesdrop on. Also, even if the third common key can be specified, the second common key is generated from the first encrypted data, and the second common key is used to generate the first common key from the third common key. Unless the key is decrypted, the first encrypted data can not be decrypted to obtain data. For this reason, it is difficult for a third party who attempts to eavesdrop on to perform cryptanalysis.

  Furthermore, in the communication system 10 according to the first embodiment, since the first common key and the second common key are random values for each data transmission, the vulnerability caused by continuing to use the same common key is obtained. It can be solved. That is, in the communication system 10 according to the first embodiment, the common key can be securely exchanged even in communication using a non-secure network.

  Further, in the common key exchange method according to the first embodiment, the amount of calculation can be reduced as compared with the key sharing method using RSA or Diffie-Hellman key exchange. Therefore, in the communication system 10 according to the first embodiment, the CPU usage of the communication apparatus can be reduced, power consumption can be reduced, and the memory capacity required for processing can be reduced.

  That is, in the communication system 10 according to the first embodiment, key exchange can be performed safely with a small amount of calculation.

Embodiment 2
Subsequently, the communication system 10A according to the second embodiment of the present invention will be described. The communication system 10A includes a communication device 1A and a communication device 2A. The configuration of the communication system 10A is the same as the configuration of the communication system 10 of the first embodiment, and is not shown.

  Subsequently, a configuration example of the communication device 1A according to the second embodiment will be described. The communication device 1A includes a first common key generation unit 101, a data encryption unit 102, a second common key generation unit 103A, a common key encryption unit 104, a combination unit 105, and a transmission unit 106. Is equipped. The configuration of the communication device 1A is the same as that of the communication device 1 of the first embodiment, and is not shown. Further, the configuration other than the second common key generation unit 103A in the communication device 1A is the same as the configuration in the communication device 1 of the first embodiment, and the description will be omitted.

  An example of the process of generating the second common key in the second common key generation unit 103A will be described using FIG.

  First, the second common key generation unit 103A generates a hash value from the first encrypted data using a predetermined hash function (step S301). The hash value is a random number sequence.

  Next, the second common key generation unit 103A extracts partial data of a predetermined bit length from a predetermined position of the hash value, and uses the extracted partial data as a second common key. A common key is generated (step S302). Note that FIG. 8 illustrates an example in which partial data of a predetermined bit length is extracted from the end of the hash value, and the extracted partial data is used as a second common key.

  Subsequently, a configuration example of the communication device 2A according to the second embodiment will be described. The communication device 2A includes a reception unit 201, a division unit 202, a second common key generation unit 203A, a common key decryption unit 204, and a data decryption unit 205. The configuration of the communication device 2A is the same as the configuration of the communication device 2 of the first embodiment, and the illustration thereof is omitted. Further, the configuration of the communication device 2A other than the second common key generation unit 203A is the same as the configuration in the communication device 2 of the first embodiment, and the description will be omitted.

  The second common key generation unit 203A generates a second common key by the same method as the second common key generation method in the second common key generation unit 103A.

  That is, the second common key generation unit 103A and the second common key generation unit 203A have a common hash function. Further, the second common key generation unit 103A and the second common key generation unit 203A obtain the common hash value by inputting the first encrypted data as an input value into the common hash function. The second common key generation unit 103A and the second common key generation unit 203A extract partial data of a predetermined bit length at a predetermined position from the acquired common hash value, and extract the partial data. Let partial data be a second common key.

  As described above, in the communication system 10A according to the second embodiment of the present invention, the second common key is used unless a third party who attempts to eavesdrop has obtained the common hash function of the communication device 1A and the communication device 1B. Can not generate. Therefore, in the communication system 10A according to the second embodiment of the present invention, the strength of the encryption can be further enhanced as compared with the communication system 10 according to the first embodiment.

Third Embodiment
Subsequently, a communication system 10B according to the third embodiment of the present invention will be described. The communication system 10B includes a communication device 1B and a communication device 2B. The configuration of the communication system 10B is the same as that of the communication system 10 according to the first embodiment, and the illustration thereof is omitted.

  Subsequently, a configuration example of the communication device 1B according to the third embodiment will be described. The communication device 1B includes a first common key generation unit 101, a data encryption unit 102, a second common key generation unit 103, a common key encryption unit 104, a combination unit 105B, and a transmission unit 106. Is equipped. The configuration of the communication device 1B is the same as the configuration of the communication device 1 of the first embodiment, and is not shown. Further, the configuration other than the coupling unit 105B in the communication device 1B is the same as the configuration in the communication device 1 of the first embodiment, and the description will be omitted. The communication device 1B may be configured to include a second shared key generation unit 103A instead of the second shared key generation unit 103.

  An example of a process of generating second encrypted data in the combining unit 105B will be described with reference to FIG.

  First, the combining unit 105B generates the divided first encrypted data by equally dividing the first encrypted data into a predetermined number of divisions (step S401). Specifically, the combining unit 105B divides the first encrypted data into n equally using the value n determined in advance by the communication device 1B and the communication device 2B. This generates the first encrypted data divided into n pieces, that is, D1 to Dn.

  Next, the combining unit 105B generates a third shared key by dividing the third common key equally into a predetermined number of divisions which is the same as the number of divisions of the first encrypted data (step S402). Specifically, the combining unit 105B divides the third common key into n equally using the value n determined in advance by the communication device 1B and the communication device 2B. This generates a third common key divided into n, ie, K1 to Kn.

  Note that the predetermined number of divisions described above in steps S401 and S402, that is, the value n, is an integer that can divide the first encrypted data and the third common key.

  Next, the combining unit 105B alternately combines the divided first encrypted data and the divided third common key to generate second encrypted data (step S403). Thereby, second encrypted data combined in the order of D1, K1, D2, K2,..., Dn-1, Kn-1, Dn, and Kn is generated.

  Subsequently, a configuration example of the communication device 2B according to the third embodiment will be described. The communication device 2B includes a reception unit 201, a division unit 202B, a second common key generation unit 203, a common key decryption unit 204, and a data decryption unit 205. The configuration of the communication device 2B is the same as the configuration of the communication device 2 of the first embodiment, and is not shown. Further, the configuration of the communication device 2B other than the dividing unit 202B is the same as that of the communication device 2 of the first embodiment, and the description will be omitted. The communication device 2B may be configured to include a second common key generation unit 203A instead of the second common key generation unit 203.

  An example of the division processing of the second encrypted data in the division unit 202B will be described with reference to FIG.

  The dividing unit 202B subtracts the key length of the third common key from the data length of the second encrypted data to calculate the data length of the first encrypted data. In addition, it is assumed that the key length of the third common key is set in advance in the division unit 202B.

  The dividing unit 202B also divides the data length of the first encrypted data by a predetermined number of divisions to calculate the division size of the first encrypted data. Specifically, the dividing unit 202B divides the first encrypted data by dividing the data length of the first encrypted data by the value n determined in advance by the communication device 1B and the communication device 2B. Calculate the size.

  The dividing unit 202B also divides the key length of the third common key by the predetermined number of divisions, which is the same as the number of divisions of the first encrypted data, to calculate the division size of the third common key. Specifically, the dividing unit 202B divides the third common key division size by dividing the key length of the third common key by the value n previously determined by the communication device 1B and the communication device 2B. calculate.

  Also, the dividing unit 202B uses the division size of the first encrypted data and the division size of the third common key to generate the first encrypted data divided from the second encrypted data and the divided first division. A common key of 3 is generated (step S501).

  In addition, in the division unit 202B, information is set which of the divided first encrypted data and the divided third common key is arranged at the head of the second encrypted data. It shall be. For example, it is assumed in advance that the second encrypted data is combined in the order of D1, K1, D2, K2,... Dn-1, Kn-1, Dn, and Kn in the dividing unit 202B. It is set. By using this information, the division size of the first encrypted data, and the division size of the third common key, the division unit 202B converts the second encrypted data into D1, D2, ... Dn-1, It is possible to generate the divided first encrypted data which is Dn, and the divided third common key which is K1, K2, ... Kn-1, Kn.

  Then, the dividing unit 202B can generate first encrypted data by combining D1, D2,... Dn−1, Dn (step S502). Also, the dividing unit 202B can generate a third common key by combining K1, K2,..., Kn-1 and Kn (step S503).

  As described above, in the communication system 10B according to the third embodiment of the present invention, the third party who tries to eavesdropping does not obtain the division size of the first encrypted data and the division size of the third common key. The second encrypted data can not be divided into the first encrypted data and the third common key. Therefore, in the communication system 10B according to the third embodiment of the present invention, the strength of encryption can be further enhanced as compared with the communication system 10 according to the first embodiment.

  Although the present invention has been described as a hardware configuration in the above-described embodiment, the present invention is not limited to this. The present invention can also be realized by causing a processor such as a CPU provided in a communication apparatus to execute a computer program for performing each process of each functional unit described above.

  In the above-mentioned example, the program can be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include tangible storage media of various types. Examples of non-transitory computer readable media are magnetic recording media (eg flexible disk, magnetic tape, hard disk drive), magneto-optical recording media (eg magneto-optical disk), CD-ROM (Read Only Memory), CD-R, CD-R / W, DVD (Digital Versatile Disc), BD (Blu-ray (registered trademark) Disc), semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (RAM) Random Access Memory)). Also, the programs may be supplied to the computer by various types of transitory computer readable media. Examples of temporary computer readable media include electrical signals, light signals, and electromagnetic waves. The temporary computer readable medium can provide the program to the computer via a wired communication path such as electric wire and optical fiber, or a wireless communication path.

  Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. The configuration and details of the present invention can be modified in various ways that can be understood by those skilled in the art within the scope of the invention.

1, 1A, 1B Communication device 2, 2A, 2B Communication device 10, 10A, 10B Communication system 101 First common key generation unit 102 Data encryption unit 103, 103A Second common key generation unit 104 Common key encryption unit 105, 105B combining unit 106 transmitting unit 201 receiving unit 202, 202B dividing unit 203, 203A second common key generation unit 204 common key decryption unit 205 data decryption unit

Claims (10)

A first communication device and a second communication device,
The first communication device is
First common key generation means for generating a first common key;
Data encryption means for encrypting data using said first common key to generate first encrypted data;
Second common key generation means for generating a second common key from a part of the first encrypted data;
A common key encryption unit that encrypts the first common key using the second common key to generate a third common key;
Combining means for combining the first encrypted data and the third common key to generate second encrypted data;
Transmitting means for transmitting the second encrypted data to the second communication device;
The second communication device is
Receiving means for receiving the second encrypted data from the first communication device;
A dividing unit that divides the second encrypted data into the first encrypted data and the third common key;
Second common key generation means for generating the second common key from a part of the first encrypted data;
Common key decryption means for decrypting the first common key from the third common key using the second common key;
Data decryption means for decrypting said data from said first encrypted data using said first common key,
Communications system.   The second common key generation means of the first communication device and the second communication device extract partial data for a predetermined bit length from the end of the first encrypted data, and the partial data The communication system according to claim 1, wherein the second common key is used.   The second common key generation unit of the first communication device and the second communication device generates a hash value from the first encrypted data using a predetermined hash function, and has a predetermined bit length The communication system according to claim 1, wherein the partial data of is extracted from a predetermined position of the hash value, and the partial data is used as the second common key. The combining means combines the third common key with the end of the first encrypted data to generate the second encrypted data.
The dividing means takes out the partial data for the bit length of the third common key from the end of the second encrypted data to obtain the second encrypted data and the first encrypted data. Split into a third common key,
The communication system according to any one of claims 1 to 3. The combining means equally divides the first encrypted data into a predetermined number of divisions, equally divides the third common key into the predetermined number of divisions, and divides the third common key into divided first encrypted data. Alternately combining the generated third common key to generate the second encrypted data,
The dividing means calculates the data length of the first encrypted data by subtracting the key length of the third common key from the data length of the second encrypted data, and calculates the first encryption The division size of the first encrypted data is calculated by dividing the data length of the data by the predetermined division number, and the key length of the third common key is divided by the predetermined division number. The division size of the third common key is calculated, and the division size of the second encrypted data is calculated based on the division size of the first encrypted data and the division size of the third common key. Generating the first encrypted data by generating the first encrypted data and the divided third common key, and combining the divided first encrypted data to generate the first encrypted data; The third common key is combined by combining three common keys. To generate a Tsukagi,
The communication system according to any one of claims 1 to 3. First common key generation means for generating a first common key;
Data encryption means for encrypting data using said first common key to generate first encrypted data;
Second common key generation means for generating a second common key from a part of the first encrypted data;
A common key encryption unit that encrypts the first common key using the second common key to generate a third common key;
Combining means for combining the first encrypted data and the third common key to generate second encrypted data;
A transmission unit configured to transmit the second encrypted data. Receiving means for receiving the second encrypted data;
A division unit that divides the second encrypted data into first encrypted data and a third common key;
Second common key generation means for generating a second common key from a part of the first encrypted data;
Common key decryption means for decrypting a first common key from the third common key using the second common key;
A data decryption unit configured to decrypt data from the first encrypted data using the first common key. A method of a communication system comprising a first communication device and a second communication device, the method comprising
The first communication device is
Generate a first common key,
Encrypting the data using the first common key to generate first encrypted data;
Generating a second common key from a portion of the first encrypted data;
Encrypting the first common key using the second common key to generate a third common key;
Combining the first encrypted data and the third common key to generate second encrypted data;
Sending the second encrypted data to the second communication device,
The second communication device is
Receiving the second encrypted data from the first communication device;
Dividing the second encrypted data into the first encrypted data and the third common key;
Generating the second common key from a portion of the first encrypted data;
Decrypting the first common key from the third common key using the second common key,
Decrypting the data from the first encrypted data using the first common key,
Method. A method of communication device,
Generate a first common key,
Encrypting the data using the first common key to generate first encrypted data;
Generating a second common key from a portion of the first encrypted data;
Encrypting the first common key using the second common key to generate a third common key;
Combining the first encrypted data and the third common key to generate second encrypted data;
Transmitting the second encrypted data. A method of communication device,
Receive the second encrypted data,
Dividing the second encrypted data into first encrypted data and a third common key;
Generating a second common key from a portion of the first encrypted data;
Decrypting the first common key from the third common key using the second common key,
Decrypting data from the first encrypted data using the first common key.

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