JP2009088641A - Transmission reception method, communication system and transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encrypting method for communication capable of ensuring sufficient secrecy without imposing a burden for processing on a transmitter side and receiver side of communication, and to provide a communication system. <P>SOLUTION: The transmitter transmits encrypted text obtained by encrypting plain text data with encryption key data to a receiver together with the encryption key data used for encryption by using a different communication channel included in a plurality of communication channels. The receiver receives the encrypted text and the encryption key data transmitted from the transmitter through a plurality of communication channels, and uses the encryption key data received together with the encrypted text as decryption key data, thereby obtaining the plain text data from the encrypted text. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission / reception method, a communication system, and a transmission apparatus that perform encrypted communication in order to ensure confidentiality.

  When data is transmitted and received between information communication terminals and the like, various encryption methods are currently proposed in order to increase the confidentiality of the communication. Particularly in wireless communication, it is relatively easy to eavesdrop on a packet of information used for communication. Therefore, even if a packet is eavesdropped by a third party, the encryption technology that makes it difficult to decipher the contents of the packet and establishes a secure communication path between the data sender and receiver is an advanced technology. It is extremely important in the information society.

  At present, there are two typical encryption techniques: a common key encryption system and a public key encryption system.

  In the common key cryptosystem, both the data sender and the receiver hold the same key, and encryption and decryption are performed using the same key. Typical examples of the common key cryptosystem include DES (Data Encryption Standard), AES (Advanced Encryption Standard), and RC4. Hereinafter, an outline of this method will be described with reference to the drawings.

  As shown in FIG. 9, first, the “information transmitting side” that performs encryption performs one-way encryption key conversion processing on the common key data and the common parameters using a hash function or the like, and sequentially generates encryption keys. To do. Here, this sequential encryption key can be considered as a “common key”. Using this common key, a ciphertext is generated by calculating an exclusive OR of plaintext data before encryption. This exclusive OR will be described later. On the other hand, the “information receiving side” that decrypts the encrypted information uses an exclusive OR of the ciphertext data using the same common key as the key used for encryption. The plaintext data can be obtained by calculating. However, the receiving side that performs decryption needs to acquire a common key from the transmitting side in advance in performing this encrypted communication. For this reason, if an eavesdropping is performed by a third party at the time of delivery of the common key, there is a risk that subsequent encrypted communication can be easily decrypted.

  Therefore, in order to increase the security strength of information communication, the public key cryptosystem performs decryption using a key different from the key used for encryption. In this method, two keys, a “public key” and a “secret key”, are used as a pair. On the other hand, encrypted plaintext data can be decrypted only by a pair of keys. The information transmitting side performs encryption using a “public key” that is disclosed to a third party out of the two key pairs created by the information receiving side, and the receiving side that receives the ciphertext receives its own “ Decrypt it using "secret key". In the public key cryptosystem, a scheme called RSA (Rivest Sharmir Adleman) is standardly used.

  With the public key cryptosystem, the risk at the time of “key delivery”, which was a weak point of the common key cryptosystem described above, is eliminated. However, this public key cryptosystem has a drawback in that it takes time to encrypt and decrypt because the mathematical processing of the algorithm employed is complicated.

  Therefore, a hybrid cryptosystem has been proposed as a technique for interpolating the weak points of the above two schemes, that is, the common key cryptosystem and the public key cryptosystem. Hereinafter, an outline of this method will be described with reference to the drawings.

  As shown in FIG. 10, in the hybrid cryptosystem, when the plaintext data is encrypted, the transmitting side encrypts it with a common key cryptosystem that is relatively easy to process, and the receiving side also uses the common key to encrypt the ciphertext. Is decrypted. When the key, which is a weak point of the common key cryptosystem, is delivered, the common key itself is encrypted with the public key out of the public key and private key pair created by the receiver, and the encrypted common key is encrypted. To the receiver. The receiving side that has received the encrypted common key decrypts the common key using its own secret key, and obtains plaintext data by decrypting the ciphertext using the decrypted common key. In this way, the processing required for encryption and decryption is reduced by using a public key cryptosystem with complicated processing only at the time of key delivery.

  If this hybrid encryption method is used, it is possible to pass the common key to a considerably safe level. Also in this encryption method, plaintext data is basically encrypted by a common key encryption method that is relatively easy to process. In the encryption of the common key cryptosystem, encryption and decryption are performed using the same key by calculating an exclusive OR by Vernam cipher. For example, as shown in FIG. 11 (A), assuming that plaintext data is all 1 bit strings, the exclusive OR (XOR) of both is calculated using the sequential encryption key as shown in the plaintext data. The ciphertext is completed. As shown in FIG. 11B, when an exclusive OR is again performed on this ciphertext using a sequential cipher key that is a correct key, the original plaintext data can be decrypted. As shown in (C), even if an exclusive OR is calculated using a fake key and decryption is attempted, the original plaintext cannot be restored.

  However, since the operation of exclusive OR performed at the time of encryption and decryption of the common key cryptosystem is a simple and regular repetitive operation, the generated ciphertext is still wiretapped by a third party. There is a risk of being deciphered if attacked by.

Therefore, when data transmission / reception is performed using multiple channels (communication channels) in an information communication terminal or the like, the transmitting side divides the generated ciphertext according to the number of channels (number of communication channels) and performs the division. A technique has been proposed in which the ciphertext is distributed to a plurality of channels and transmitted to prevent the third party from eavesdropping and decrypting the entire contents of the generated ciphertext.
JP 2000-115162 A

  In Patent Document 1 described above, when the receiving side decrypts the ciphertext received from each channel (communication path), the ciphertext is divided and redistributed to a plurality of channels (communication paths) and transmitted. The reception apparatus needs a lot of calculation time for the reconfiguration, and processing delay may occur. Therefore, it is not suitable for cases where it is required to avoid processing delay as much as possible, such as wireless communication. In particular, when a large amount of data is distributed and transmitted to many channels (communication channels) at a time, the number of divided ciphertexts increases according to the number of channels (number of communication channels). Increasingly, processing delay will further increase.

  Further, in Patent Document 1 described above, a third party transmits an encryption key for encrypting data by the transmission side and a part of the divided ciphertext that is transmitted by the transmission side to a specific channel (communication path). If acquired, a part of the transmitted ciphertext can be decrypted. Therefore, if a third party who has eavesdropped on the ciphertext and has succeeded in partial decryption has knowledge of the data to be transmitted, the possibility of full-text prediction by partial decryption of the ciphertext cannot be avoided. . Therefore, even if the ciphertext is divided and distributed according to the number of channels (number of communication channels), data confidentiality cannot be ensured.

  Accordingly, an object of the present invention made in view of such circumstances is to provide a transmission / reception method, a communication system, and a communication system that can ensure sufficient secrecy without burdening the processing performed on both the transmission side and the reception side that perform information communication. It is to provide a transmission device.

  In order to solve the above-described problems, a transmission / reception method according to the first invention is a transmission / reception method using a plurality of communication channels performed between a transmission device and a reception device, wherein the transmission device comprises: Generating encryption key data for encrypting plaintext data, encrypting the plaintext data using the generated encryption key data to generate a ciphertext, and the encryption generated in the encryption step Transmitting the key data and the ciphertext through different communication channels, and receiving the receiver receiving the cipher key data and the ciphertext transmitted from the transmitting device; A decrypting step of decrypting the ciphertext using the encryption key data received in the receiving step as decryption key data to obtain the plaintext data is a first feature.

  According to the first feature, the transmission device transmits the ciphertext and cipher key data (one-way pseudo-random number to be described later) used for generating the ciphertext to each of different assigned communication channels in a plurality of communication channels. By separately transmitting at, the receiving device can easily perform decoding after receiving and can speed up the arithmetic processing, thereby reducing processing delay. In addition, the third party cannot obtain the ciphertext and the encryption key data unless the third party eavesdrops on the data transmitted on all channels (the ciphertext and the encryption key data used to generate the ciphertext), Furthermore, since the ciphertext cannot be deciphered, it is possible to realize communication maintaining the cipher strength. Here, the plurality of communication channels are (A) a plurality of communication channels capable of transmitting and receiving data at the same frequency band and the same timing, (B) a plurality of communication channels having different frequency bands, and (C) a frequency. This means that a plurality of communication channels having different bands and different data transmission / reception timings are assigned or assigned.

 In the transmission / reception method according to the second invention, when N communication channels (N is a natural number of 2 or more) are used as the plurality of communication channels, in the encryption step, the transmission device sequentially transmits the plaintext data. A plurality of the encryption key data for encryption is generated, and in the transmission step, the transmission device generates less than the N encryption key data among the plurality of encryption key data generated in the encryption step. Transmitting to the receiving apparatus is a second feature.

  According to the second feature, since the transmission device does not need to generate encryption key data in accordance with the number of channels, communication confidentiality can be improved.

  In the transmission / reception method according to the third invention, in the transmission step, the transmission device transmits a part of the encryption key data generated in the encryption step together with the ciphertext, and in the reception step, the The receiving device receives a part of the encryption key and the ciphertext transmitted from the transmitting device, and after executing the receiving step, grasps the encryption key data that has not been transmitted from the transmitting device, and A decryption key generation step of generating untransmitted encryption key data as decryption key data, wherein in the decryption step, the reception device together with the decryption key data generated in the decryption key generation step A third feature is that the plaintext data is obtained by decrypting the ciphertext using the encryption key data received in step 1 as the decryption key data.

  According to the third feature, the transmission device does not need to generate encryption key data according to the number of channels, and further does not need to transmit all the generated encryption key data to the reception device. Also, the receiving device acquires all the encryption key data used for encryption by the transmitting device by grasping and generating the encryption key data not transmitted from the transmitting device from the information shared with the transmitting device. Can do. In addition, the transmission device can also transmit using a plurality of channels including data that is not related to encryption (for example, fake data). Thereby, the confidentiality of communication can be improved.

  In the transmission / reception method according to a fourth aspect of the invention, in the encryption step, the transmission device generates the encryption key data having the same data length as the plaintext data, and after the encryption step, the transmission device Each data array having the same position from the reference with respect to either the start or end of each data array (bit string) of the encrypted data generated in the encryption step and the ciphertext A conversion step of converting the encrypted data and the ciphertext by selecting code data (bit) in (bit string) and transposing the selected code data (bit) according to a predetermined rule; In the transmitting step, the transmitting device transmits the ciphertext converted in the converting step and the encryption key data. To.

  According to the fourth feature, the transmitting apparatus transposes code data (bits) at the same position from the reference, with either the start or end of each data array (bit string) having the same data length as the reference. By performing the processing, when receiving the ciphertext and the encryption key subjected to the transposition processing, the receiving device performs the decryption without returning the code data transposed by the transposition processing to the original position. It is possible to reduce the processing burden on the receiving device while improving confidentiality.

  In the transmission / reception method according to a fifth aspect of the present invention, in the encryption step, the transmission device generates the encryption key data having the same data length as the plaintext data, and after the encryption step, the transmission device Further includes a second conversion step of converting the encryption key data and the ciphertext generated in the encryption step according to a second predetermined rule, and in the transmission step, the transmission device includes: , Transmitting the encryption key data and the ciphertext converted in the second conversion step, and in the reception step, the receiving device converts the encryption key data converted in the second conversion step and the encryption key data And receiving the ciphertext, and after the receiving step, grasping the second predetermined rule, and based on the grasped second predetermined rule, the encryption key received in the receiving step And over data and said ciphertext, an inverse transformation step of returning to said original of the encryption key data encrypted, the fifth, further comprising.

  According to the fifth feature, confidentiality can be enhanced by performing a second predetermined rule, for example, transposition processing and / or shift conversion of arbitrarily selected code data (bits).

  In the transmission / reception method according to the sixth invention, after the encryption step, the transmission device sets a communication channel for transmitting the encryption key data and the ciphertext generated in the encryption step, respectively. Then, the encryption key data and the ciphertext are divided so that the data length can be transmitted in the transmission frame of each set communication channel, and the divided encryption key data and the ciphertext are divided into third A third conversion step for converting the data according to a predetermined rule, wherein in the transmission step, the transmission device transmits the encryption key data and the ciphertext converted in the third conversion step. In the receiving step, the receiving device receives the cipher key data and the ciphertext converted in the third converting step, and after the receiving step, the third predetermined rule is received. A second inverse transform for grasping and returning the cipher key data and the ciphertext received in the receiving step to the original cipher key data and the ciphertext based on the third predetermined rule And a step further comprising a step.

  According to the sixth feature, depending on the channel, the frequency band and the data length that can be transmitted in the transmission frame may be different, so the block is divided into blocks having the corresponding data length, 3 predetermined rules, for example, transposition processing of arbitrarily selected code data (bits), code data (bits) in the same block, and between different blocks (A. the same encryption key data or the same encryption) Concealment can be enhanced by performing the conversion between blocks in a sentence) (B. non-identical encryption key data or between blocks in a ciphertext) and / or performing shift conversion.

  The transmission / reception method according to a seventh aspect of the present invention further includes a determining step in which the transmitting device determines the number of the encryption key data according to a configuration and / or content of the plaintext data, and in the encryption step, The transmitting device generates the number of encryption key data determined in the determining step, and the receiving device recognizes the number of the encryption key data generated by the transmitting device in the decryption key generating step. The seventh feature is that the untransmitted encryption key data is grasped.

  According to the seventh feature, since the number of encryption key data to be generated can be set according to the configuration and / or contents of the plaintext data, an encryption that has not been transmitted by generating encryption key data greater than the number of communication channels. Key data can be increased, and communication confidentiality can be improved.

An eighth aspect of the transmission / reception method according to the eighth aspect of the present invention is that the transmission apparatus and the reception apparatus perform transmission / reception using a MIMO (Multi Input Multi Output) communication scheme.

 In order to solve the above-described problems, a communication system according to a ninth aspect of the invention includes a transmission device and a reception device, and is a communication system that transmits and receives using a plurality of communication channels. An encryption key data generation unit for generating encryption key data for encrypting data, and encryption for generating ciphertext by encrypting the plaintext data using the encryption key data generated by the encryption key data generation unit A transmission unit that transmits the encryption key data generated by the encryption key data generation unit and the ciphertext generated by the encryption unit to the reception device through different communication channels, A receiving device that receives the encryption key data and the ciphertext transmitted from the transmitting device; decrypts the ciphertext using the encryption key data received by the receiving unit; and the plaintext Get data A decoding unit, in that it comprises a ninth aspect of.

 A transmitting device according to a tenth invention is a transmitting device that transmits data using a plurality of communication channels, and includes an encryption key data generating unit that generates encryption key data for encrypting plaintext data, An encryption unit that encrypts the plaintext data using the encryption key data generated by the encryption key data generation unit to generate a ciphertext, the encryption key data generated by the encryption key data generation unit, and the encryption A tenth feature includes a transmission unit that transmits the ciphertext generated by the unit via a different communication channel.

  According to the present invention, since the transmission device transmits the encryption key together with the ciphertext, the decryption calculation processing in the reception device can be speeded up, and the processing delay can be reduced.

  Further, if all the data transmitted through a plurality of channels is not acquired, the third party cannot decrypt the ciphertext, so that communication with high encryption strength can be maintained. Furthermore, since not all of the encryption keys used to generate the ciphertext are transmitted to the receiving device, the ciphertext cannot be decrypted even if all the transmitted data is acquired. It is difficult, and it is possible to sufficiently secure the confidentiality of communication while dramatically improving the encryption strength. For this reason, since the transmitting apparatus does not need to perform key exchange frequently, processing in encryption of the transmitting apparatus can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically illustrating a communication system including a transmission device 100 and a reception device 300 according to an embodiment of the present invention. In the present embodiment, communication is performed using a MIMO communication method, and both the transmission apparatus 100 and the reception apparatus 300 have a plurality of antennas, and the transmission is performed on a communication channel corresponding to the plurality of antennas. The device 100 transmits a plurality of different data simultaneously, while the receiving device 300 receives the plurality of different data simultaneously.

  The transmission apparatus 100 in FIG. 2 includes common information and an application 10 that supplies plaintext data, an encryption strength determination unit 11 that determines a predetermined encryption strength from the plaintext data, and each communication channel used for communication. A storage unit 12 that stores channel information, a one-way pseudorandom number generation unit 13 that generates one-way pseudorandom numbers, and an arithmetic processing unit 14 that performs arithmetic processing on the plaintext data and the one-way pseudorandom numbers (encryption key data). And an encryption unit 15 that generates an encrypted transmission ciphertext to be transmitted to the receiving device 300, and a transmission unit 16 that transmits the transmitted ciphertext to the receiving device 300.

  The application 10 outputs plaintext data to be encrypted and transmitted to the receiving device 300 to the encryption strength determination unit 11 and the arithmetic processing unit 14.

  The encryption strength determination unit 11 determines the strength for encrypting the plaintext data from the configuration and / or contents of the plaintext data output from the application 10, and describes information related to the determined encryption strength (hereinafter referred to as encryption strength information). Is output to the storage unit 12 and the encryption unit 15. In addition, after determining the encryption strength of the plaintext data, the number of one-way pseudorandom numbers generated by the one-way pseudorandom number generation unit 13 with reference to information (details will be described later) stored in the storage unit 12 and The number of one-way pseudorandom numbers to be transmitted to the receiving apparatus 300 is set based on the cryptographic strength, and information on the number of generated one-way pseudorandom numbers and the number of one-way pseudorandom numbers to be transmitted (hereinafter referred to as one-way pseudorandom number generation information and Are output to the storage unit 12 and the one-way pseudorandom number generation unit 13. At this time, the generated number of one-way pseudo random numbers is increased as the determined encryption strength is higher. Further, the numbers assigned to the one-way pseudorandom numbers to be transmitted to the receiving device and the one-way pseudorandom numbers not to be transmitted are stored in, for example, the encryption strength information supplied from the encryption strength determination unit 11 or the channel information storage unit 121 of the storage unit 12. It is determined by the number of communication channels used in the communication to be performed. However, the number of one-way pseudorandom numbers transmitted to the receiving apparatus 300 is less than the number of communication channels used in the MIMO communication with the receiving apparatus 300. Furthermore, conversion information for performing conversion processing (details will be described later) in the encryption unit 15 is generated and output to the storage unit 12.

  The storage unit 12 is a common information storage unit 120 that stores common information between the transmission device 100 and the reception device 300, and a channel information storage that stores channel information of communication channels that the transmission device 100 uses for communication with the reception device 300. Unit 121.

  The common information storage unit 120 includes common parameters as common information between the transmission device 100 and the reception device 300, cryptographic strength information output from the cryptographic strength determination unit 11, unidirectional pseudorandom number generation information, conversion information (details will be described later). .) Is remembered. Among these, the common parameter is information that can generate a one-way pseudorandom number by using a one-way function such as a hash function. The common information including the common parameters is stored in the common information storage unit 120 in advance, or includes the conversion information generated by the encryption strength determination unit 11, and then the public key information with the receiving device 300 is obtained. The transmitting apparatus 100 encrypts the common information with the public key paired with the private key of the receiving apparatus 300 and is stored in the public key system key exchanging unit (not shown) to be exchanged. The common information is shared and stored by acquiring the common information by receiving and decrypting with the secret key. The receiving apparatus 300 performs decoding based on the shared common information. Further, the common parameter may be a common parameter calculated from a common key obtained by key exchange as in a general hybrid cryptosystem.

  The channel information storage unit 121 stores channel information of each communication channel used by the transmission device 100 for communication with the reception device 300. For example, the maximum number of usable communication channels based on the number of transmission antennas in the transmission device 100 and the number of reception antennas in the reception device 300, information on the data length that can be transmitted in one transmission frame of the transmission frame corresponding to each communication channel, The modulation method (modulation class) in each communication channel is stored, and the encryption unit 16 performs encryption by referring to the stored information (details will be described later).

  The one-way pseudo-random number generation unit 13 uses a one-way function as a common parameter supplied from the common information storage unit 120 in the storage unit 12 and a one-way pseudo-random number supplied from the encryption strength determination unit 11. The number of generations based on the generation information is generated. At this time, the one-way pseudo-random number generation unit 13 generates one long one-way pseudo-random number, and extracts the necessary generation number. The random length of the extracted one-way pseudo-random number depends on the length of the plain text data. Further, the transmission device 100 may be configured to include a plurality of one-way pseudorandom number generation units 13 for improving the encryption strength. Then, the generated one-way pseudorandom number is output to the arithmetic processing unit 14.

  In addition, the one-way pseudo-random number generation unit 13 receives a one-way pseudo-random number (hereinafter, referred to as a transmission random number) to be transmitted to the receiving device 300 among the generated one-way pseudo-random numbers, and improves the encryption strength. A one-way pseudorandom number (hereinafter referred to as an untransmitted random number) to be discarded without being transmitted to the device 300 is determined based on the one-way pseudorandom number generation information. Then, the one-way pseudo-random number assigned as a transmission random number (encryption key data) to be transmitted to the receiving apparatus 300 is output to the encryption unit 15.

  The arithmetic processing unit 14 sequentially performs arithmetic processing on the plaintext data output from the application 10 by exclusive OR, using the one-way pseudorandom number (encryption key data) output from the one-way pseudorandom number generation unit 13. The result (hereinafter referred to as calculation result information) is output to the encryption unit 15.

  When performing encryption, the encryption unit 15 uses the first predetermined method (predetermined rule or rule) for the calculation result information output from the calculation processing unit 14 and the transmission random number output from the one-way pseudorandom number generation unit 13. A first conversion unit 150 that converts in accordance with a second predetermined rule) to obtain a plurality of intermediate ciphertexts, and a communication channel that transmits each intermediate ciphertext obtained by the first conversion unit 150 is selected, and each communication A data division unit 151 that divides the intermediate ciphertext into a plurality of blocks based on a data length that can be transmitted in one transmission frame in a transmission frame corresponding to a channel, and the data division unit 151 divides the intermediate ciphertext into a plurality of blocks A second conversion unit 152 configured to convert the intermediate ciphertext according to a second predetermined method (third predetermined rule) and generate a transmission ciphertext;

  The first conversion unit 150 converts the calculation result information output from the calculation processing unit 14 and the transmission random number output from the one-way pseudo-random number generation unit 14 according to a first predetermined method. Converting according to the first predetermined method means performing transposition processing of arbitrary code data (bits) included in each data array (bit string) of calculation result information and transmission random numbers, or performing shift processing, Means. These conversion processes are performed based on encryption strength information and conversion information output from the storage unit 12. Then, the plurality of intermediate ciphertexts obtained after performing the conversion process are output to the data dividing unit 151.

  The data division unit 151 sets a communication channel for transmitting each of the plurality of intermediate ciphertexts output from the first conversion unit 150. The communication channels set at this time are different communication channels, and one intermediate ciphertext is not set to be transmitted through a plurality of communication channels. Then, the intermediate ciphertext is divided into a plurality of blocks based on the data length that can be transmitted in one transmission frame in the transmission frame in the set communication channel, and the intermediate ciphertext composed of the divided plurality of blocks is second To the converter 152.

  The second conversion unit 152 converts the intermediate ciphertext composed of a plurality of blocks output from the data division unit 151 according to a second predetermined method. The conversion according to the second predetermined method means that transposition processing of arbitrary code data (bits) included in the data array (bit string) of each block is performed or shift processing is performed. These conversion processes are performed based on encryption strength information and conversion information output from the storage unit 12. A plurality of transmission ciphertexts obtained after the conversion process is output to the transmission unit 16.

  The transmission unit 16 transmits a plurality of transmission ciphertexts output from the encryption unit 15 (second conversion unit 152) to the reception device 300 through a communication channel associated with the encryption unit 15 (data division unit 151). Send.

  3 includes a reception unit 30 that receives a transmission ciphertext from the transmission device 100, a storage unit 31 that stores common information with the transmission device 100 and channel information in each communication channel used for communication. The encryption strength determination unit 32 that determines a predetermined encryption strength from the common information, the decryption unit 33 that decrypts the transmission ciphertext received from the transmission device 100, and the one-way pseudorandom number generation unit 34 that generates a one-way pseudorandom number And an arithmetic processing unit 35 that performs arithmetic processing of the decrypted ciphertext and the one-way pseudorandom number to obtain plaintext data, and an application 36 that processes the plaintext data.

  The receiving unit 30 receives a plurality of transmission ciphertexts transmitted from the transmission device 100 via a plurality of communication channels, and outputs the received transmission ciphertexts to the decryption unit 33.

  The storage unit 31 stores common information storage unit 310 that stores common information between the reception device 300 and the transmission device 100, and each channel information of communication channels that the reception device 300 uses to communicate with the transmission device 100. A channel information storage unit 311.

  The common information storage unit 310 stores common parameters as common information between the reception device 300 and the transmission device 100. And it is the information which can produce | generate a one-way pseudorandom number by using one-way functions, such as a hash function, for a common parameter. The common information including the common parameters is stored in advance in the common information storage unit 310 or stored in a public key method key exchange unit (not shown) that exchanges public key information with the transmission device 100. The transmission apparatus 100 encrypts the common information with the public key paired with the private key of the apparatus 300, and the received common information is received by the reception apparatus 300 and decrypted with the private key. By doing so, the common information is shared and stored. The receiving apparatus 300 performs decoding based on the shared common information. Further, the common parameter may be a common parameter calculated from a common key obtained by key exchange as in a general hybrid cryptosystem.

  The channel information storage unit 311 stores channel information of each communication channel used by the reception device 300 for communication with the transmission device 100. For example, the maximum number of usable communication channels based on the number of reception antennas in the reception device 300 and the number of transmission antennas in the transmission device 100, information on the data length that can be transmitted in one transmission frame of the transmission frame corresponding to each communication channel, The modulation scheme (modulation class) and the like in each communication channel are stored, and the decoding unit 33 performs decoding with reference to the stored information (details will be described later).

  The encryption strength determination unit 32 determines the encryption strength based on the output from the storage unit 31 (common information storage unit 310), and supplies information (encryption strength information) related to the determined encryption strength to the decryption unit 33. Further, after determining the encryption strength, the number of one-way pseudo-random numbers generated by the transmission device 100 is grasped, and the number of untransmitted random numbers not transmitted from the transmission device 100 is grasped. Then, information regarding the grasped number of untransmitted random numbers (hereinafter referred to as untransmitted random number information) is output to the one-way pseudorandom number generator 34.

  When decrypting the transmission ciphertext output from the receiving unit 30, the decryption unit 33 performs inverse conversion according to the third predetermined method (third predetermined rule), and converts the intermediate ciphertext composed of a plurality of blocks. A third conversion unit 330 to be obtained, a data integration unit 331 for returning an intermediate ciphertext composed of a plurality of blocks obtained by the third conversion unit 150 to the intermediate ciphertext before the division, and the data integration unit 331 A fourth conversion unit 332 that inversely converts the plurality of intermediate ciphertexts obtained in accordance with a fourth predetermined method (second predetermined rule) to obtain calculation result information and a transmission random number.

  The 3rd conversion part 330 carries out reverse conversion of the output transmission ciphertext output from the receiving part 30 according to a 3rd predetermined system. Inverse conversion in accordance with the third predetermined method means that the second predetermined method performed in the transmitting apparatus 100 is grasped and included in the data array (bit string) of each block of the intermediate ciphertext composed of a plurality of blocks. This means that the code data (bits) subjected to the transposition processing is returned to the position before the transposition processing, and the data array (bit string) of each block subjected to the shift processing is returned to the state before the shift processing. These inverse conversion processes are performed based on the conversion information included in the common information supplied from the storage unit 31. Then, an intermediate ciphertext composed of a plurality of blocks obtained after performing the inverse conversion process is output to the data integration unit 331.

  The data integration unit 331 returns the intermediate ciphertext composed of the plurality of blocks output from the third conversion unit 330 to the intermediate ciphertext before the division, and sends the obtained plurality of intermediate ciphertexts to the fourth conversion unit 332. Output.

  The fourth conversion unit 332 performs inverse conversion on the plurality of intermediate ciphertexts output from the data integration unit 331 according to a fourth predetermined method. Inverse conversion according to the fourth predetermined method means that the first predetermined method (second predetermined rule) is grasped and each data array (bit string) of calculation result information and transmission random numbers performed in the transmission device 100 is obtained. ) To return the arbitrary code data (bits) included in) to the position before the transposition process, and to return the data array (bit string) of the operation result information subjected to the shift process and each transmission random number to the state before the shift process. Means. These inverse conversion processes are performed based on the conversion information included in the common information supplied from the storage unit 31. Then, the calculation result information and the transmission random number obtained after performing the inverse conversion process are output to the calculation processing unit 35.

  The one-way pseudorandom number generator 34 generates a one-way pseudorandom number using a one-way function for the common parameter supplied from the storage unit 31 (common information storage unit 310). At this time, the one-way pseudo-random number to be generated is an untransmitted random number that has not been transmitted to the receiving apparatus 300 by the transmitting apparatus 100 based on the untransmitted random number information supplied from the cryptographic strength determination unit 32. At this time, when there is no untransmitted random number that has not been transmitted from the transmission device 100 to the reception device 300, the one-way pseudorandom number generation unit 34 does not generate an untransmitted random number. Then, the generated untransmitted random number is output to the arithmetic processing unit 35.

  The arithmetic processing unit 35 performs exclusive OR operation on the calculation result information supplied from the decoding unit 33 in order by the transmission random number output from the decoding unit 33 and the untransmitted random number output from the one-way pseudorandom number generation unit 34. The obtained plaintext data is output to the application 36.

  The application 36 processes the plain text data output from the arithmetic processing unit 35.

  In addition, the transmitting device 100 transposes code data at the same position from the reference in the encryption unit 15 (first conversion unit 150) with reference to either the start end or the end in the data array of the calculation result information and the transmission random number. When the conversion process is performed according to the first predetermined method (predetermined rule), the receiving apparatus 300 performs the inverse conversion process according to the fourth predetermined method in the decoding unit 33 (fourth conversion unit 332). It is not necessary to return the data code (bit) in the plurality of intermediate ciphertexts to the original position and obtain the operation result information and the transmission random number. In this case, in the receiving apparatus 300, a plurality of intermediate ciphertexts obtained by the decryption unit 33 (data integration unit 331) are output to the arithmetic processing unit 35 as they are, and the arithmetic processing unit 35 performs exclusive OR. Since the plaintext data can be obtained even if the arithmetic processing is performed, the fourth conversion unit 332 in the decryption unit 33 may not be included in the configuration. Thereafter, in the present embodiment, the encryption unit 15 (first conversion unit 150) in the transmission device 100 uses either the start end or the end in the data array (bit string) of the operation result information and the transmission random number as the first predetermined method. With reference to the above, a description will be given of the case of transposing code data (bits) at the same position from the reference (in accordance with a predetermined rule).

  Also, the encryption strength determination unit 11 in the transmission device 100 does not need to set the number of transmission random numbers to be transmitted to the reception device 300 according to the number of communication channels used for communication, and is generated by the transmission device 100. The number of transmission ciphertexts may be less than the number of communication channels. In this case, since fake data may be transmitted on a specific communication channel, it is possible to adjust the encryption strength according to the degree to which confidentiality is required.

  Next, each process performed by the arithmetic processing unit 14 and the encryption unit 15 in the transmission device 100 and the decryption unit 33 and the arithmetic processing unit 35 in the reception device 300 will be described with reference to FIGS.

  First, when performing arithmetic processing by exclusive OR, if the start positions of the bit string (data array) of plaintext data and the bit string of one-way pseudo-random numbers are shifted, the arithmetic processing is not performed correctly. Therefore, the one-way pseudo random number needs to be generated with the same data length as the plain text data. The positions of the plaintext data bit string and the unidirectional pseudo-random bit string need to be strictly aligned, as shown in FIG. 4, for example. Note that the numbers and symbols shown in FIG. 4 merely represent the positional relationship of the bit strings, and do not represent the data of the bits (code data) themselves.

  FIG. 5A shows calculation processing by exclusive OR and generation of calculation result information as a calculation result in the calculation processing unit 14 in the transmission apparatus 100. The arithmetic processing unit 14 outputs the plaintext data output from the application 10 and the one-way pseudo random number (the transmission random number 1, the transmission random number 2, and the untransmitted random number) generated by the one-way pseudo random number generation unit 13 (encryption key data). ) And an operation result by exclusive OR is calculated, and calculation result information is calculated.

  FIG. 5B shows either the start or end of the bit string of the operation result information and the transmission random numbers (transmission random number 1 and transmission random number 2) in the first conversion unit 150 of the encryption unit 15 in the transmission apparatus 100. And a plurality of intermediate ciphertexts (intermediate ciphertext 1, intermediate ciphertext 2) by transposition conversion processing based on the first predetermined method (predetermined rule) described above. And generation of intermediate ciphertext 3). In this case, for example, calculation result information and transmission in the calculation result information output from the calculation processing unit 14 and the one-way pseudo random number (transmission random number 1 and transmission random number 2) output from the one-way pseudo random number generation unit 13. Random number 1 and each bit included in transmission random number 1 and transmission random number 2 are transposed to generate intermediate ciphertext (intermediate ciphertext 1, intermediate ciphertext 2, and intermediate ciphertext 3).

  FIG. 5C shows an intermediate ciphertext (intermediate ciphertext 1, intermediate ciphertext 2, and intermediate ciphertext) output from the first conversion unit 150 in the data dividing unit 151 of the encryption unit 15 in the transmission apparatus 100. The sentence 3) is divided into a plurality of blocks based on the data length that can be transmitted in one transmission frame in a transmission frame in the set communication channel, and generation of an intermediate ciphertext composed of the plurality of divided blocks is shown. Yes.

  FIG. 5 (D-1) shows an intermediate ciphertext composed of a plurality of blocks output from the data dividing unit 151 by the second conversion unit 152 of the encryption unit 15 in the transmission device 100 to the reception device 300. The generation of a transmission ciphertext to be transmitted is shown. In the second conversion unit 152, conversion processing by transposing bits included in a block of an intermediate ciphertext composed of a plurality of blocks as a second predetermined method (third predetermined rule), for example, intermediate ciphertext In 1, the conversion process of transposing the bit X and the bit Y is performed to generate transmission ciphertexts (transmission ciphertext 1, transmission ciphertext 2, and transmission ciphertext 3).

  Further, the second conversion unit 152 of the encryption unit 15 in the transmission device 100 may perform conversion processing by shift processing as the second predetermined method. For example, as shown in FIG. 5D-2, the bit string (before the shift) in the block of the intermediate ciphertext 1 is moved by, for example, +2 in the X-axis direction. Note that moving (shifting) the bit string by +2 in the X-axis direction is referred to as [X: +2] for convenience. The transmission ciphertext (transmission ciphertext 1, transmission ciphertext 2, and the transmission ciphertext 2 that has been subjected to the conversion process of moving the bit in the bit string +2 in the X-axis direction and moving the bit protruding from the original bit length to the starting point of the bit string as it is, A transmission ciphertext 3) may be generated. Also, bits may be shifted between different blocks.

  FIG. 6A-1 shows code data transposed in the third conversion unit 330 of the decoding unit 33 in the reception device 300 by the transmission device 100 according to the second predetermined method (third predetermined rule). Is converted according to the third predetermined method to the original position. For example, in the transmission ciphertext 1, an inverse conversion process for transposing the bit Y and the bit X is performed, and an intermediate ciphertext composed of a plurality of blocks (intermediate ciphertext 1, intermediate ciphertext 2, and intermediate ciphertext 3). Get.

  FIG. 6B shows an intermediate ciphertext (intermediate ciphertext 1, intermediate ciphertext 2, and intermediate ciphertext 3) composed of a plurality of blocks in the data integration unit 331 of the decryption unit 33 in the receiving device 300. Integration processing for restoring the original is performed to obtain intermediate ciphertexts (intermediate ciphertext 1, intermediate ciphertext 2, and intermediate ciphertext 3).

  FIG. 6C shows calculation processing by exclusive OR and generation of plain text data as a calculation result in the calculation processing unit 35 in the receiving apparatus 300. The arithmetic processing unit 35 outputs the calculation result information and transmission random numbers (transmission random number 1 and transmission random number 2) output from the decoding unit 33, and the one-way pseudo random number (untransmitted) generated by the one-way pseudo random number generation unit 34. A plaintext data is obtained by performing an arithmetic operation by exclusive OR with a random number.

  In addition, in the second conversion unit 152 of the encryption unit 15 in the transmission device 100, when conversion processing by shift processing is performed as the second predetermined method (third predetermined rule) (in FIG. 5 ( D-2)), a process of returning the bit string shifted by the transmitting apparatus 100 according to the second predetermined method to the original position according to the third predetermined method. For example, as shown in FIG. 6A-2, the shifted bit string is moved by, for example, −2 in the X-axis direction. A conversion process is performed in which the bits in the bit string are moved by -2 in the X-axis direction, and the bits protruding from the original bit length are moved as they are to the end point of the bit string.

  In FIGS. 5 and 6, as a first predetermined method, the calculation result information and the transmission random number (transmission random number 1 and transmission random number 2) in the bit string of the bit string are used as a reference, and the same position from the reference is set. Although the case where the conversion process of transposing certain code data is performed (in accordance with a predetermined rule) has been described, the first predetermined method in the first conversion unit 150 of the encryption unit 15 is not limited to this, and the calculation Conversion processing for transposing arbitrary bits of the result information and transmission random numbers (transmission random number 1 and transmission random number 2) may be performed, or conversion processing by shift processing may be performed (according to the second predetermined rule). If). In this case, the receiving device 300 includes a fourth conversion unit 332 in the decryption unit 33, and the fourth conversion unit 332 performs intermediate ciphertext (intermediate ciphertext 1, intermediate ciphertext 2, And the reverse conversion process of the intermediate ciphertext 3) is performed to obtain operation result information and transmission random numbers (transmission random number 1 and transmission random number 2). Since the inverse conversion process at this time is the same as that of the third predetermined method described above (see FIGS. 6A-1 and 6A-2), details are omitted.

  Hereinafter, with reference to the conceptual diagram of FIG. 7, a data flow in the encryption processing of the transmission apparatus 100 according to the embodiment of the present invention will be described.

  The flow from the top to the bottom in FIG. 7A represents the flow of one-way pseudorandom numbers. As a premise to generate one-way pseudo random numbers, generate multiple one-way pseudo random numbers using a hash function etc. for the common parameters shown in the upper part of the figure, and transmit random numbers and untransmitted from the generated one-way pseudo random numbers Determine a random number. As described above, the common parameter supplied from the common information storage unit 120 becomes a one-way pseudo-random number when the one-way pseudo-random number generation unit 13 performs the conversion process.

  The flow from the left to the right in the lower part of FIG. 7A represents the flow of data when plaintext data is sequentially subjected to arithmetic processing by exclusive OR to become operation result information. First, the application 10 of the transmission device 100 supplies plaintext data to be encrypted to the encryption strength determination unit 11. The encryption strength determination unit 11 determines the strength for encrypting the plaintext according to a predetermined condition from the configuration and / or content of the plaintext data, and the one-way pseudorandom number generated by the one-way pseudorandom number generation unit 13 based on this Determine the number of generations and the number of random numbers sent. The common information storage unit 120 stores information regarding the number of one-way pseudorandom numbers, and transmits common information including information regarding the number of one-way pseudorandom numbers to the reception device 300 via the transmission unit 16. The common information storage unit 310 in 300 is shared. Then, the arithmetic processing unit 14 sequentially performs arithmetic processing for obtaining an exclusive OR with the one-way pseudo-random number generated by the one-way pseudo-random number generating unit 13 to generate calculation result information, and the calculation result information Is output to the encryption unit 15. Further, the one-way pseudo-random number generator 13 outputs the one-way pseudo-random number to the arithmetic processing unit 14 and then discards the untransmitted random number for improving the encryption strength.

  The flow from left to right in FIG. 7B is a transmission selected from the calculation result information output from the calculation processing unit 14 and the one-way pseudorandom number generated by the one-way pseudorandom number generation unit 13. A flow of data when a random number is transmitted to the receiving apparatus 300 is shown. The first conversion unit 150 of the encryption unit 15 converts the calculation result information generated by the calculation processing unit 14 and the transmission random number generated by the one-way pseudo-random number generation unit 13 according to a first predetermined method. To generate an intermediate ciphertext. Further, in the data dividing unit 151, based on the channel information stored in the channel information storage unit 121, the data length that can be transmitted in one transmission frame of a transmission frame in a communication channel that performs transmission associated with each intermediate ciphertext is set. Based on this, a dividing process for dividing the intermediate ciphertext into a plurality of blocks is performed. After the division, a conversion process is performed according to the second predetermined method, each transmission ciphertext is generated, and transmitted to the receiving apparatus 300 through the associated communication channel.

  Hereinafter, with reference to the conceptual diagram of FIG. 8, a data flow in the decoding process of the receiving apparatus 300 according to the embodiment of the present invention will be described.

  The flow from left to right in FIG. 8A represents the data flow when the transmission ciphertext output from the reception unit 30 is decrypted by the reception device 300. The third conversion unit 330 of the decryption unit 33 performs a conversion process (inverse conversion process) on the transmission ciphertext received by the reception unit 30 according to a third predetermined method to generate an intermediate ciphertext composed of a plurality of blocks. And output to the data integration unit 331. Further, in the data integration unit 331, based on the channel information stored in the channel information storage unit 311, the intermediate data is divided based on the data length that can be transmitted in one transmission frame of the transmission frame corresponding to the transmitted communication channel. An integration process for restoring the ciphertext is performed and output to the arithmetic processing unit 35. Depending on the contents of the first predetermined method, the fourth conversion unit in the decoding unit 33 obtains the calculation result information and the transmission random number according to the fourth predetermined method, and then calculates the calculation result information and the transmission. The random number is output to the arithmetic processing unit 35. These decoding processes are performed based on the common information transmitted from the transmission apparatus 100.

  The flow from the top to the bottom in FIG. 8B represents the flow of one-way pseudorandom numbers. As a premise for generating a one-way pseudo random number, a plurality of one-way pseudo random numbers are generated using a hash function or the like for the common parameter shown in the upper part of the figure, and the generated one-way pseudo random numbers are transmitted from the transmission device 100. Select an unsent random number that has not been sent. As described above, the common parameter supplied from the common information storage unit 120 becomes a one-way pseudo-random number when the one-way pseudo-random number generation unit 13 performs the conversion process.

  The flow from the left to the right in the lower part of FIG. 8B represents the data flow when the intermediate ciphertext sequentially performs arithmetic processing by exclusive OR to obtain plaintext data. First, the arithmetic processing unit 35 of the receiving device 300 performs arithmetic processing by exclusive OR using the intermediate ciphertext output from the decryption unit 33. Furthermore, the arithmetic processing by exclusive OR using the untransmitted random number which the transmission apparatus 100 output from the one-way pseudorandom number 34 did not transmit is performed with respect to the information obtained by the arithmetic processing. The data obtained in this way becomes plain text data, the plain text data is supplied to the application 36, and a series of decryption processing ends. Depending on the contents of the first predetermined method, the fourth conversion unit in the decoding unit 33 obtains calculation result information and a transmission random number according to the fourth predetermined method. An exclusive OR using an untransmitted random number that is not transmitted by the transmitting device 100 that is output from the one-way pseudo-random number 34 after the arithmetic processing unit 35 performs an arithmetic operation based on the exclusive OR using the transmission random number. Perform the calculation process by.

  If the encryption and decryption processes are performed as described above, the encryption strength can be significantly increased. Since this method hardly increases the processing burden, it is advantageous when transmitting / receiving large amounts of data using multicarrier communication such as WiMAX (Worldwide Interoperability for Microwave Access). . Furthermore, in the encrypted communication according to the present embodiment, the number of one-way pseudo-random numbers to be generated is set according to the contents of plaintext data, and then a one-way pseudo-random number to be transmitted and a one-way pseudo-random number to be transmitted are selected. Furthermore, it is not always necessary to generate a transmission ciphertext according to the communication channel to be used. For example, false data may be transmitted on a specific communication channel, and thus the degree of confidentiality required. The cipher strength can be adjusted as desired.

  Further, in the present invention, the transmission random number and the untransmitted random number are determined from the one-way pseudo-random number generated based on the common parameter. However, the present invention is not limited to this. The one-way pseudo-random number generator 13 determines the one-way pseudo-random number generated based on the common parameter, while the transmission random number includes a one-way pseudo-random number generator different from the one-way pseudo-random number generator 13; The different one-way pseudo-random number generation unit determines the one-way pseudo-random number generated without using the common parameter. As a result, a third party who performs eavesdropping cannot maintain the communication with higher confidentiality because the ciphertext cannot be decrypted unless all the data transmitted through the plurality of channels is reliably acquired. it can.

  In addition, this invention is not limited only to embodiment mentioned above, Many change or deformation | transformation is possible. For example, in the present embodiment, the transmission device 100 and the reception device 200 perform wireless communication, but the present invention can also be applied when performing wired communication.

  In addition, the transmission device and the reception device according to the present invention can perform transmission / reception of transmission ciphertext with each other, instead of only performing transmission or reception together. In this case, the transmission device includes each component of the reception device, and the reception device includes each component of the transmission device.

It is a figure which shows the communication system structure of this Embodiment. It is a block diagram which shows schematic structure of the principal part of the transmitter of this Embodiment. It is a block diagram which shows schematic structure of the principal part of the receiver of this Embodiment. It is a figure explaining the positional relationship between plaintext data and a one-way pseudorandom number. It is a figure explaining the process in the transmission apparatus of this Embodiment. It is a figure explaining the process in the receiver of this Embodiment. It is a conceptual diagram explaining the flow of an encryption process of a transmitter. It is a conceptual diagram explaining the flow of a decoding process of a receiver. It is a conceptual diagram explaining the conventional common key encryption system. It is a conceptual diagram explaining the conventional hybrid encryption system. It is a figure explaining the arithmetic processing of the exclusive OR of the common key encryption system by a Burnham encryption.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Transmitting device 300 Receiving device 10 Application 11 Encryption strength determination unit 12 Storage unit 13 One-way pseudorandom number generation unit 14 Operation processing unit 15 Encryption unit 16 Transmission unit 120 Common information storage unit 121 Channel information storage unit 150 First conversion unit 151 Data division unit 152 Second conversion unit 30 Reception unit 31 Storage unit 32 Encryption strength determination unit 33 Decryption unit 34 One-way pseudorandom number generation unit 35 Arithmetic processing unit 36 Application 310 Common information storage unit 311 Channel information storage unit 330 Third conversion unit 331 Data integration unit 332 Fourth conversion unit

Claims (10)

A transmission / reception method using a plurality of communication channels performed between a transmission device and a reception device,
The transmitting device is
Generating encryption key data for encrypting plaintext data, encrypting the plaintext data using the generated encryption key data, and generating a ciphertext;
Transmitting the encryption key data and the ciphertext generated in the encryption step through different communication channels,
The receiving device is
A reception step of receiving the encryption key data and the ciphertext transmitted from the transmission device;
Using the encryption key data received in the reception step as decryption key data, decrypting the ciphertext and obtaining the plaintext data; and
A transmission / reception method comprising: When N (N is a natural number of 2 or more) communication channels are used as the plurality of communication channels,
In the encryption step,
The transmitting device is
Generating a plurality of the encryption key data for sequentially encrypting the plaintext data;
In the transmission step,
The transmitting device is
Out of a plurality of encryption key data generated in the encryption step, the less than N encryption key data is transmitted to the receiving device.
The transmission / reception method according to claim 1. In the transmission step,
The transmitting device is
A part of the encryption key data generated in the encryption step is transmitted together with the ciphertext;
In the receiving step,
The receiving device is
Receiving a part of the encryption key and the ciphertext transmitted from the transmission device;
After executing the receiving step,
Further comprising a decryption key generation step of grasping the untransmitted encryption key data from the transmission device and generating the untransmitted encryption key data as decryption key data
In the decoding step,
The receiving device is
Along with the decryption key data generated in the decryption key generation step, the ciphertext is decrypted using the encryption key data received in the reception step as decryption key data to obtain the plaintext data.
The transmission / reception method according to claim 2. In the encryption step,
The transmitting device is
Generating the encryption key data having the same data length as the plaintext data,
After the encryption step,
The transmitting device is
Based on either the start or end of each data array of the encrypted data generated in the encryption step and the ciphertext, the code data in each data array at the same position is selected from the reference And
A conversion step of converting the encrypted data and the ciphertext by transposing the selected code data according to a predetermined rule;
In the transmission step,
The transmitting device is
Transmitting the ciphertext and the encryption key data converted in the conversion step;
The transmission / reception method according to any one of claims 1 to 3. In the encryption step,
The transmitting device is
Generating the encryption key data having the same data length as the plaintext data,
After the encryption step,
The transmitting device is
A second conversion step of converting the encryption key data generated in the encryption step and the ciphertext according to a second predetermined rule;
In the transmission step,
The transmitting device is
Transmitting the encryption key data converted in the second conversion step and the ciphertext;
In the receiving step,
The receiving device is
Receiving the encryption key data and the ciphertext converted in the second conversion step;
After the receiving step,
The second predetermined rule is grasped, and based on the grasped second predetermined rule, the encryption key data and the ciphertext received in the receiving step are converted into the original encryption key data and the original The reverse conversion step back to ciphertext
The transmission / reception method according to any one of claims 1 to 3, further comprising: After the encryption step,
The transmitting device is
Each of the communication channels for transmitting the encryption key data and the ciphertext generated in the encryption step is set, so that the data length can be transmitted in the transmission frame of each of the set communication channels, Further comprising a third conversion step of dividing the encryption key data and the ciphertext, and converting the divided encryption key data and the ciphertext according to a third predetermined rule,
In the transmission step,
The transmitting device is
Transmitting the encryption key data and the ciphertext converted in the third conversion step;
In the receiving step,
The receiving device is
Receiving the encryption key data and the ciphertext converted in the third conversion step;
After the receiving step,
The third predetermined rule is grasped, and based on the third predetermined rule, the encryption key data and the ciphertext received in the reception step are converted into the original encryption key data and the ciphertext. A second inverse transformation step back to
The transmission / reception method according to claim 1, further comprising: The transmitting device is
A determination step of determining the number of the encryption key data according to the configuration and / or content of the plaintext data,
In the encryption step,
The transmitting device is
Generate the number of encryption key data determined in the determination step,
The receiving device is:
In the decryption key generation step, after grasping the number of the encryption key data generated by the transmission device, grasp the untransmitted encryption key data;
The transmission / reception method according to any one of claims 2 to 6. The transmission device and the reception device perform transmission / reception by a MIMO (Multi Input Multi Output) communication method.
The transmission / reception method according to any one of claims 1 to 7. A communication system having a transmission device and a reception device and transmitting / receiving using a plurality of communication channels,
The transmitter is
An encryption key data generation unit for generating encryption key data for encrypting plaintext data;
An encryption unit that encrypts the plaintext data using the encryption key data generated by the encryption key data generation unit and generates a ciphertext;
A transmission unit that transmits the encryption key data generated by the encryption key data generation unit and the ciphertext generated by the encryption unit to the reception device through different communication channels;
The receiving device is:
A receiving unit for receiving the encryption key data and the ciphertext transmitted from the transmission device;
Using the encryption key data received by the receiving unit, decrypting the ciphertext and obtaining the plaintext data;
A communication system comprising: A transmission device that transmits data using a plurality of communication channels,
An encryption key data generation unit for generating encryption key data for encrypting plaintext data;
An encryption unit that encrypts the plaintext data using the encryption key data generated by the encryption key data generation unit and generates a ciphertext;
A transmission unit that transmits the encryption key data generated by the encryption key data generation unit and the ciphertext generated by the encryption unit over different communication channels;
A transmission device comprising:

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