JP2002217897A - Transmitter and receiver ciphering part of data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deciphering of a cryptographic key by ciphering data except for prescribed numerals. SOLUTION: This transmitter for partial ciphering of data is provided with a specific numeral ciphering part 13 for ciphering the data excluding only prescribed numerical data with a common ciphering key in constitution, where data communication is performed by using the common ciphering key, for transmitting the data with the excluded specific numerical data. The transmitter is provided with a specific numeral decoding part 23 for deciphering received data with the common ciphering key, excluding only the prescribed numerical data from the received data, to restore the received data together with the decoded prescribed numerical data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data encryption device for preventing the leakage of an encryption key in a computer system, particularly when encrypting and transmitting numeric data.

[0002]

2. Description of the Related Art In order to share highly confidential data, it is necessary to encrypt the data. Various encryption methods have been devised. As an encryption method for performing processing at low cost, there is a substitution cipher using an encryption key. Substitution encryption is a method of replacing transmission data with another character one by one using a secret key. As a replacement method, a method of shifting characters to the next character by the number of the encryption key in the order of “aiueo” or “1, 2, 3”, a method of replacing by a conversion table, an exclusive OR of the character and the encryption key are used. There are methods to take.

[0003] In the substitution cipher, the encryption key used when encrypting on the data transmitting side and the encryption key used when decrypting on the data receiving side must be common. Also, the common encryption key needs to be a secret key that is not disclosed to anyone other than the data sender and receiver. Considering a case where data is encrypted and stored in a database, a data sender is a person who inputs data to the database, and a data receiver is a person who reads data from the database. As a feature of encrypting data via a database, the length of data to be encrypted at one time is short, but the number of times of encryption is very large. When encrypting such data, a simple substitution cipher that uses an encryption key as a secret key is used. Although simple substitution ciphers have low encryption strength, they have the feature of being able to perform high-speed processing at low cost. This feature is very effective when the number of data is large.

Next, the operation of the conventional substitution cipher will be described. FIG. 8 is a diagram for explaining an example in which data is encrypted by a substitution cipher that shifts simple characters using an encryption key, and data is transmitted and received via a database. The data transmission side generates encrypted data 103 using the transmission data 101 and the encryption key 102, and transmits this. The receiving side decrypts the received encrypted data 104 using the same encryption key 105 as the transmitting side. The decrypted data becomes the received data 106.

Now, consider the case where the substitution cipher is applied to data including numbers. FIG. 9 shows transmission data 1
The figure shows that a number as the encrypted data 113 is generated by using the substitution encryption key 112 for the number as 11. However, when the data is a numeral, the value itself of the substitution encryption key 112 appears in the encryption data 113 of the digit whose transmission data 111 is 0 from the number 4567 or 123 appearing in the circle of the encryption data 113. That is, the number in the circle, 4
567 or 123. If there is only one numerical data, it is not known. However, when it repeatedly appears as shown in FIGS. 9A, 9B, and 9C, one of the numerical values is easily 0 from the part and the other is the secret key. Is deciphered.

[0006]

The conventional encryption key system using the substitution cipher is configured as described above. When a large number of data, such as money data stored in a database, is generated as a large number of transmission data, 0 is used. In the lower digits where the ratio represented by is large, the encryption key appears in the encrypted data as it is, and there is a problem that the encryption key can be easily decrypted by the difference method of comparing a plurality of data.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem.
It is intended to prevent the encryption key from appearing in the encrypted data as it is, that is, to prevent the decryption of the encryption key, by performing encryption except for a specific numerical value represented by, for example,.

[0008]

A data partial encryption transmission device according to the present invention, in a configuration for performing data communication using a common encryption key, performs encryption using a common encryption key while excluding only predetermined numeric data. A specific numeral encrypting unit is provided to perform transmission together with the excluded specific numeral data.

Further, the predetermined numeral data is provided with a replacement encryption unit for replacing with another predetermined numeral, and the numeral to be encrypted is an encrypted output value other than the predetermined numeral replaced by the specific numeral encryption unit. I tried to get.

Further, the specific numeral encrypting section for encrypting other numerals excluding the predetermined numeral data performs a numerical conversion using a shift type secret key.

A data partial encryption receiving apparatus according to the present invention, in a configuration in which data communication is performed using a common encryption key, wherein a specific numeral for performing decryption using a common encryption key by excluding only predetermined numerical data from received data. A decoding unit is provided to restore the received data together with the decoded predetermined numeric data.

[0012] Furthermore, a predetermined number data is provided with a permutation decoding unit for substituting and decoding another predetermined number, and the number to be encrypted is a number other than the predetermined number replaced by the specific number decoding unit. The encrypted output value was used and restored to the original numeric data.

Further, the specific numeral decoding unit for decrypting other numeral data excluding a predetermined numeral performs a numerical conversion using a shift type secret key corresponding to the transmitting side.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A specific configuration and operation of the present invention in which the secret key is not easily known in a simple manner will be described. FIG. 1 is a system diagram showing a pair of a data partially encrypted transmission side and a data partially encrypted reception side in the present embodiment. FIG. 2 is a diagram showing a relationship between data and a key in FIG.
Indicates the whole data partially encrypted transmission side, and 2 indicates the same data partially encrypted reception side. 11 is a cutout unit that cuts out the numbers in the numeric data encryption unit 10 digit by digit, 12
Is a replacement encryption unit that extracts only a predetermined number, for example, '0' and replaces it with another predetermined number, for example, '9'
Reference numeral 13 denotes a specific number encryption unit for encrypting a number other than the predetermined number 0, and reference numeral 14 denotes a character encryption unit for extracting characters and codes other than numeric data from transmission data and encrypting them. Reference numeral 21 denotes a cutout unit for extracting a digit from the received data and cutting it out in units of one digit in the numeric data decoding unit 20;
Is a permutation decoding unit for restoring the replaced number corresponding to the transmitting side, 23 is a specific number decoding unit for restoring the original number from a predetermined number, for example, an encrypted number other than 9 after substitution A character decoding unit 24 extracts and decodes codes other than numbers from the received data. 3 is a database.

The operation of this system will be described with reference to FIGS. In this case, it is assumed that the defined exclusion number is “0”. The data partial encryption transmission side partially encrypts, for example, the transmission data 41 shown in FIG. The cutout unit 11 cuts out the digit data in the transmission data 41 one digit at a time, and the replacement encryption unit 12 outputs
Replace digit 0 with 9 Further, the specific numeral encryption unit 13
The first three digits “356” are encrypted using the encryption key 42 to obtain “470”. These numbers are combined to obtain encrypted data 43, which is stored in the database. On the data-partially encrypted receiving side, the database 3 is accessed and the encrypted data 51 (this is equal to the encrypted data 43)
Then, the numerical data is cut out digit by digit by the cutout unit 21, and the permutation decoding unit 22 extracts the specified lower four digits of the permutation digit '9' and converts it to 0. Further, the specific numeral decryption unit 23 decrypts the first three digits “470” using the encryption key 52 to obtain “356”. These are combined and the received data 53 is restored.

FIG. 3 is an operation explanatory diagram for explaining the operation of encryption in the present embodiment, and corresponds to FIG. 9 for explaining the conventional operation. In the present embodiment, the encryption key that appears in a circle in the conventional example becomes 9 in this case, and it turns out that it is a number in any of (a) to (d) of FIG. The secret key number is unknown. Moreover, the numbers are replaced numbers, not the original numbers. Therefore, the confidentiality of the numbers can be improved with a simple configuration. This method is extremely effective when hiding the value of a number without hiding that the data is a number. The numbers before and after are completely encrypted, so even if a third party knows that they are numbers, the true numbers are unknown. According to this method, for example, the possibility that the secret key is decrypted from the amount data is reduced, so that the security of not only the amount data but also other data encrypted with the same secret key can be improved. In the present embodiment, an example in which the present invention is applied to a database has been described. Further, the determined number may be any one of 0 to 9.

Embodiment 2 FIG. In the present embodiment, a case will be described in which a so-called shift-type secret key and a shift-type substitution encryption method are used for a specific-number encryption unit and a specific-number decryption unit.
FIG. 4 is a diagram for explaining the principle of the shift-type substitution encryption method. FIG. 5 is a diagram in which the specific numeral encryption unit in the configuration of FIG. 5 is an operation flowchart of the numerical data encryption unit 10b according to the present embodiment. In the figure, the predetermined number to be replaced is 0. The secret key is “1, 2, 3, 4, 5, 6, 7”, and a specific example is shown in FIG. 2 corresponding to the original data.

The operation of the shift-type substitution encryption method will be described.
The principle is to make the numeric sequence of the secret key correspond to the numeric sequence of transmitted data, but to form a shift ring except for the digit after substitution (in this case 9). That is, in the example of FIG. 2, 3 of the transmission data advances by the number 1 indicated by the secret key to 4; 5 of the transmission data advances by the number 2 indicated by the secret key to 7; It proceeds by 3 as shown, and in this case it becomes 9, but since 9 is the number after replacement, it is excluded and becomes 0.
According to the flowchart of FIG. 5, at step (hereinafter abbreviated as S) 71, the specific numeral encrypting unit 13b excludes the numeral 9 after the numeral substitution from the encrypted output. The numerical data cut out digit by digit by the cut-out unit 11 is the specific numeric encryption unit 13b if the original number is other than 0 in S74.
Determines the numerical value y as the encrypted data by the logic explained in principle in S77 to S81. If the number is to be replaced in S74, the replacement encryption unit 12 replaces the number 0 with 9 in S75. Thus, the encrypted data 43 of FIG. 2 is specifically obtained.

FIG. 6 is a diagram for explaining the principle of decryption corresponding to FIG. 4 for encryption, and FIG. 7 is a diagram corresponding to FIG. It is an operation | movement flowchart of the part 20b. The number after the replacement is 9, and it is to be returned to the original 0. As is apparent from the above-mentioned encryption principle diagram, the received single-digit number of the encrypted data 51 is converted to the one-digit number on the shift ring in FIG. 6 based on the previously transmitted secret encryption key 52 corresponding to the arrow direction. Go ahead and restore the original number. The flowchart of FIG. 7 shows a specific operation.
If 1 and the secret encryption key 52 have the values shown in FIG. 2, the received data 53 to be restored is obtained.

[0020]

As described above, according to the present invention, since the specific numeral encrypting section for performing encryption while excluding predetermined numeral data is provided, it is possible to know the secret key with a relatively simple configuration. Has the effect of preventing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a data partial encryption system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between data and a secret key in FIG.

FIG. 3 is an explanatory diagram of an operation of encryption according to the first embodiment.

FIG. 4 is a diagram illustrating the principle of shift-type substitution encryption in Embodiment 2 of the present invention.

FIG. 5 is a numeric data encryption unit 1 according to the second embodiment.
It is an operation | movement flowchart of 0b.

FIG. 6 is a diagram for explaining the principle of shift-type substitution decoding in Embodiment 2 of the present invention.

FIG. 7 is a numeric data decoding unit 2 according to the second embodiment.
It is an operation | movement flowchart of 0b.

FIG. 8 is a diagram illustrating a conventional substitution encryption method.

FIG. 9 is an explanatory diagram of an operation of conventional substitution encryption.

[Explanation of symbols]

1 data partial encryption transmission side, 2 data partial encryption reception side, 3 database, 12, 12b replacement encryption section,
13, 13b Specific numeral encryption unit, 22, 22b Replacement decryption unit, 23, 23b Specific numeral decryption unit.

Claims (6)

[Claims] In a configuration in which data communication is performed using a common encryption key, a specific number encryption unit that performs encryption using the common encryption key while excluding only predetermined numeric data is provided. A data partial encryption transmission device for transmitting together with numeric data. 2. A method according to claim 1, wherein the predetermined numeric data includes a replacement encryption unit that replaces the predetermined numeric data with another predetermined number, and the number to be encrypted is an encrypted output value other than the predetermined number replaced by the specific numeric encryption unit. 2. The data partial encryption transmission device according to claim 1, wherein: 3. A specific numeral encrypting unit for encrypting another numeral excluding a predetermined numeral data is configured to perform a numerical conversion using a shift type secret key.
The data partial encryption transmission device according to the above. 4. In a configuration in which data communication is performed using a common encryption key, a specific numeral decoding unit for performing decryption using the common encryption key by excluding only predetermined numeral data from received data is provided. A data-partially-encrypted receiving device for restoring received data together with the predetermined numerical data. 5. A predetermined numeral data is provided with a permutation decoding unit for substituting and decoding another predetermined numeral, and a numeral to be encrypted is a numeral other than the predetermined numeral replaced by the specific numeral decoding unit. 5. The data partial encryption receiving apparatus according to claim 4, wherein the encrypted partial output value is used to restore the original numeric data. 6. A specific numeral decoding unit for decrypting other numeral data excluding a predetermined numeral, performs numerical conversion using a shift type secret key corresponding to a transmitting side. The data partial encryption receiving device according to claim 4.