JPH0472841A - Data transmission method - Google Patents

Abstract

PURPOSE:To disable decoding of a cryptographic code when a key data is stolen at the write of, e.g. a cryptographic key management section and a decoding key management section by revising a cryptographic key and a decoding key so as to be always made correspondent interlockingly during data transmission. CONSTITUTION:A cryptographic key management section 5B and a decoding key management section 7B store plural cryptographic keys and decoding keys and any of the cryptographic keys of the management section 5B is selected at random for each cryptographic processing of a prescribed number of transmission data to revise a decoding key periodically at random. Moreover, a relevant decoding key of the management section 7B is selected for each decoding of a prescribed number of received data and the decoding key is revised at random in interlocking with the revision of the cryptographic key. Thus, the data transmission of the cryptographic processing system is implemented while revising the cryptographic key automatically at random during the transmission and the decoding of a cryptographic code is almost disabled and the reliability of security is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to data transmission in which data such as two numbers is encrypted using an encryption method using an encryption key on the sender side and a decryption key on the receiver side. Regarding the method.

[Conventional technology]

Conventionally, data transmission using an encryption method using this type of key involves wireless or wired transmission between an encryption device (IA) on the sending side and a decryption device (28) on the receiving side, as shown in Figure 2. Road (3)
It is done by combining.

The encryption device (18) is equipped with an encryption unit (4) and an encryption key management unit (5A) formed of a memory, etc., and this management unit (58) is Holds one encryption key for given specific data.

The decryption device (2A) also includes a decryption unit (6) and a decryption key management unit (7Δ) formed of a memory, etc., and this management unit (78) stores 1' decryption keys corresponding to the encryption key. Hold the key.

Then, the transmission data Di such as two numbers and characters from the encryption device (18) is sequentially sent to the encryption section (4), and this encryption section (4) stores the encryption key of the encryption key management section (5A). is encrypted using

This encryption is performed, for example, by four arithmetic operations on the transmission data Di and the encryption key data Ka.

Then, the encrypted transmission data Di is transferred to the transmission path (3)
The data are sequentially transmitted to the decoding device (2A) via the decoding device (2A).

Next, in the decryption device (2A), the encrypted transmission data Di is sequentially sent to the decryption unit (6) as received data.
).

Then, the decryption unit (6) sends the decryption key management unit (78)
The received data is decrypted using the decryption key of , and the same decrypted data Do as the transmitted data Di is reproduced.

Note that the decryption is performed by, for example, an inverse operation of the encryption using the data Kb of the decryption key.

[Problem to be solved by the invention]

In the case of the conventional data transmission method, the encryption key and decryption key are
Only the set is used, and the content (data) of the image style does not change unless it is rewritten by a host device or manually.

In order to prevent decryption errors caused by mismatching keys between encryption and decryption, at least the contents of the image format are not rewritten and changed during data transmission, and normally the image format is It is used fixed to the given content.

Therefore, for example, if the data Ka and Kb of each image style are stolen when writing to the management sections (5A) and (7A), the encryption will be extremely easily decrypted and the data will be stolen, making the reliability of confidentiality low. There is a problem.

An object of the present invention is to provide a data transmission method in which encryption keys and decryption keys are periodically changed to improve reliability of confidentiality.

[Failure to solve the problem]

In order to achieve the above object, in the data transmission method of the present invention, an encryption key management section that holds a plurality of encryption keys is provided on the sending side, and an encryption key corresponding to each encryption key of the encryption key management section is provided on the receiving side. A decryption key management unit that holds a plurality of decryption keys is provided, and a random selection signal for the sending side is formed based on generation of an error correction code for each fixed number of transmitted data to be encrypted, and the random selection signal for the sending side is provided. Based on the above, each encryption key of the encryption key management unit is randomly selected every time the certain number of transmitted data is encrypted, and the encryption key is periodically and randomly changed, and the certain number of received data is decrypted. A receiving side random selection signal corresponding to the sending side random selection signal is formed based on the generation of an error correction code, etc., and each decryption key management unit performs each decryption based on the receiving side random selection signal. A key is randomly selected each time the fixed number of received data is decrypted, and the decryption key is randomly changed in conjunction with the change of the encryption key.

[For production]

In the case of the data transmission method of the present invention configured as described above, the encryption key management section and the decryption key management section each hold a plurality of encryption keys and decryption keys, unlike conventional methods.

Then, based on a random selection signal from the transmitting side, one of the encryption keys of the encryption key management section is randomly selected every time a certain number of transmission data is encrypted, and becomes the key for the next encryption.

Also, based on the random selection signal on the receiving side that corresponds to the random selection signal on the sending side, the decryption key corresponding to the selected encryption key of the encryption key management unit is stored in the decryption key management every time a certain number of received data is decrypted. It is selected from the following sections and becomes the key for the next decryption.

Therefore, by periodic random selection, the encryption key and the decryption key are changed in conjunction so that they always correspond to each other during data transmission.

Then, there are multiple keys for encryption and decryption, and since the image quality changes randomly at a set period during data transmission, for example, when the encryption key management section and decryption key management section write the key data, Even if it is stolen, the code cannot be deciphered,
Confidentiality is more reliable.

〔Example〕

One embodiment will be described with reference to FIG.

In FIG. 1, (IB) and (2B) are encryption devices and decryption devices corresponding to the devices (IA) and (IB) in FIG. ) have each.

(8) is an error correction code generation unit for forming a random selection signal on the transmitting side, which is provided before the encryption unit (4), and (5B) is an encryption code provided in place of the management unit (5A) in Fig. 2. It is a key management unit that sequentially stores addresses A, , A2 . ..., An
The first, second, ..., Nth encryption key data K
a.

Holds Kaz,..., Kan.

(9) is an error correction code generation unit for forming a random selection signal on the received data side, which is provided after the decoding unit (6);
B) is a decryption key management unit provided in place of the management unit (7A) in FIG. 2, which sequentially stores addresses 88. Δ2. ...
.

Data Kb, Kbz, . . . , Kbn of each decryption key corresponding to each encryption key of the management unit (5B) is held on the surface.

The management units (5B) and (7B) are each formed of a memory or the like, and are configured in advance by a host device or manually to store each encryption key data Ka, ~Kan, each decryption key data Kb,
~Kbn is written.

In addition, the generation units (8) and (9) are formed by error correction code generation circuits having the same configuration, for example, having a counter function and a function of generating an error correction code of the DEXUM method, and are used to generate a code that is supplied to the encryption unit (4). The transmission data Dj before encoding and the received data after decoding output from the decoding unit (6), that is, the decoded data Do, are each divided into a certain number M (M is 1.
... integer) every time it is counted, the sending side.

Error correction code signals Ax and Ay are respectively generated as random selection signals on the receiving side.

The error correction code signals Ax and Ay are formed by a known error correction code generation process using one or more of M pieces of transmission data Di and decoded data DO, and address A2, . .

Then, when data transmission is started, the device (IB).

By the start operation of (2B) etc., the generation part (8), (9
) is initialized, and both signals Ax and Ay are at address A1.
becomes the signal.

At this time, data Ka of the first encryption key is read from the management section (5B) to the encryption section (4), and data Ka of the first decryption key is read from the management section (7B) to the decryption section (6). Data Kb is read out, and the encryption key and decryption key are initialized.

The transmission data Di supplied to the encryption unit (4) via the generation unit (8) is encrypted using the first encryption key.

Furthermore, the encrypted transmission data is sequentially transmitted to the decryption device (2B) via the transmission path (3).

At this time, the received transmission data Di is supplied as received data to the decryption unit (6), and the decryption unit (6) correctly decrypts the received data using the first decryption key.

Then, the M transmission data Di are sequentially encrypted using the first encryption key, and when a certain number of encryptions are completed, the generation unit (8) generates a new error correction code and converts the signal Ax into change.

At this time, the signal Ax randomly changes to one of addresses 8 to An, depending on the contents of the transmission data Di used for code generation.

Furthermore, based on the change in the signal Ax, the encryption key data Kax read from the management unit (5B) is changed to the first encryption key data Kax immediately after the M-th transmission data Di is encrypted.
, changes to the encryption key data of the specified address.

Further, each received data based on the M old transmission data is decrypted using the first decryption key, and when the decryption of the constant is completed, the generation unit (9) generates the data in the generation unit (8). A new error correction code that is the same as the original code is generated and the signal is changed.

Based on the change in the signal, the decryption key data Kby read from the management unit (7B) also changes from the first decryption key data Kb to the decryption key data of the designated address.

At this time, since the signals Ax and Ay have the same address, the decryption key read from the management section (7B) becomes a key corresponding to the encryption key read from the management section (5B).

Therefore, the next M pieces of transmitted data Di are encrypted using a new randomly selected encryption key, and the M pieces of received data based on this encryption are encrypted using a decryption key changed according to the encryption key. is decrypted.

From then on, every time the encryption of M pieces of transmission data Di is completed,
The encryption key is randomly changed to one of the encryption keys held in the management unit (5B).

Furthermore, each time the decryption of M pieces of received data is completed, the decryption key is also randomly changed to the corresponding decryption key of the management unit (7B) in conjunction with the change of the encryption key.

Since the encryption key changes periodically and randomly during data transmission, the encryption key data Ka, ~Kan.

Even if the decryption key data Kb, -Kbn are stolen, the order and period of their changes are completely unknown, making decryption almost impossible.

Note that, in order to make deciphering even more difficult, it is desirable to adjust the period of change in consideration of the appearance of the bit pattern of the transmission data Di.

Further, the circuit configuration and the method of forming random selection signals on the transmitting side and the receiving side are not limited to the embodiments.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

A plurality of encryption keys and decryption keys are held in the encryption key management unit (5B) and decryption key management unit (7B), and one of the encryption keys in the management unit (5B) is stored every time a certain number of transmitted data are encrypted. The management unit (7B) randomly selects and periodically changes the encryption key, and every time a certain number of received data are decrypted.
The corresponding decryption key is selected, and the decryption key is changed randomly in conjunction with the change of the encryption key, so the encryption key is automatically and randomly changed during transmission, and the data of the encryption method is At this time, deciphering the code becomes almost impossible, dramatically improving the reliability of confidentiality.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the data transmission method of the present invention, and FIG. 2 is a block diagram of a conventional example. (IB)...Encryption device, (2B)...Decryption device, (3)...Transmission path, (4)...Encryption unit, (5B
)...Encryption key management section, (6)...Decryption section, (7B
)...Decryption key management unit, (8), (9)...Error correction code generation unit. Agent Patent Attorney Fuji 1) Ryutabe

Claims (1)

[Claims] (1) A data transmission method in which the sender sequentially encrypts and transmits transmitted data such as numbers and characters using an encryption key, and the receiver sequentially decrypts the encrypted received data using a decryption key. In this method, an encryption key management section that holds a plurality of encryption keys is provided on the sending side, and a decryption key management section that holds a plurality of decryption keys corresponding to each encryption key of the encryption key management section is provided on the reception side, A random selection signal on the sending side is formed based on the generation of an error correction code for each fixed number of transmitted data to be transmitted, and based on the random selection signal on the sending side, each encryption key in the encryption key management unit is set to the fixed number. The encryption key is randomly selected every time a certain number of transmitted data are encrypted, and the encryption key is periodically and randomly changed, and each time a certain number of received data is decoded, the transmitting side forming a receiving-side random selection signal corresponding to a random selection signal, and randomly selecting each decryption key of the decryption key management unit each time the certain number of received data is decrypted, based on the receiving-side random selection signal; A data transmission method characterized in that the decryption key is changed randomly in conjunction with the change of the encryption key.