JP4392808B2 - Encryption processing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an encryption processing system that encrypts transmission data and transmits the data to a receiving side through a communication line.
[0002]
[Prior art]
In general, when encryption is performed on an arbitrary file, the encryption is collectively performed by one encryption method using one encryption key for the file. Also, in order to respond to attacks on ciphertexts by third parties, the encrypted text is further divided, and the divided data is sequentially distributed over the line, and the distributed data transmitted over the line A method of rearranging the images again in the original order has been proposed (Japanese Patent Laid-Open No. 3-108830).
[0003]
[Problems to be solved by the invention]
A certain cryptanalysis method, for example, a known plaintext attack (in the case of e-mail, etc., using the fact that a lot of typical text appears in the export part, a common key is created based on a pair of plaintext and ciphertext known to the attacker. If the encryption of a part of a file is broken by an attack that is derived), there is a risk that the encryption of the whole file will be broken in the same manner.
In addition, as proposed in Japanese Patent Laid-Open No. 3-108830, when a file is divided after being encrypted, it becomes difficult for a third party to decrypt the file, but it is difficult to decrypt a part of the file. It does not change even if it spreads to the whole.
An object of the present invention is to solve the above-described problems, and it is an object of the present invention to improve the concealability of the entire file and maintain high security.
[0004]
[Means for Solving the Problems]
The present invention provides a dividing means for dividing a file according to a file dividing method stored in an IC card, an encryption method for a file stored in an IC card, and encrypting each file divided by the dividing means with an encryption key The encryption means to perform, and the order in which each file is maintained or rearranged before or after encryption, and when rearranged, an order indicating the order and the last child file is added. A replacement means, a transmission means for transmitting each encrypted file as a separate file, and an index indicating the order of each file or the last child file transmitted by the transmission means and rearranged. Decrypting that deletes the index when it is, decrypts each individual file using the encryption conditions, decrypts all files, and then reintegrates each file A stage, and in the encryption process, a mathematical expression for determining the length of the file to be divided by the dividing means and its initial value, a mathematical expression for determining the encryption method of the subdivided file and its initial value, A mathematical expression for obtaining a key used for each encryption and an initial value thereof are set.
Further, the present invention is characterized in that a dummy file is further added to the divided file.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is an overall view of an encryption processing system according to the present invention.
The transmission side includes a transmission terminal device 1 and an encryption device 2, and the transmission terminal device 1 sends encrypted transmission data to the communication line 5 via the encryption device 2. The receiving side includes a decrypting device 3 and a receiving terminal device 4. The encrypted data is received by the receiving terminal device 4 and decrypted by the decrypting device 3.
[0006]
FIG. 2 is a block diagram showing functions of the encryption device 2 of the present invention.
The encryption device 2 includes a file dividing unit 21 that divides a data file to be transmitted, a dummy file adding unit 22 that adds a dummy file as necessary, a rearranging unit 23 that rearranges the divided files, and an encryption of each divided file. A split file encryption unit 24 is provided.
[0007]
The file dividing means 21 has, for example, one or a plurality of mathematical formulas to divide, randomly determines a mathematical formula to be used, arbitrarily sets an initial value, and determines a file division position from the mathematical formula, Alternatively, an appropriate method such as a method of generating a random number and using this to determine the file division position is used. Each divided file is provided with an index indicating the division position, or a table indicating the division position is created.
[0008]
The dummy file adding means 22 generates and adds a certain number of dummy files of a certain size, or adds the dummy files to be added in accordance with the number of file divisions and the size of the dummy files. Adds some information indicating that, for example, an index.
[0009]
The rearranging means 23 determines the order in which the files are arranged by generating random numbers, or having one or a plurality of mathematical expressions and arbitrarily setting initial values.
[0010]
The divided file encryption means 24 has a plurality of encryption methods and encryption keys, and encrypts the entire divided file with one encryption method and encryption key, or for each divided file or several files. Encryption is performed by changing the encryption method and encryption key. Also, encryption may be performed on a part of the file.
[0011]
As schematically shown in FIG. 3, the original data F is divided into a plurality of files F ₁ , F ₂ ... F _n by the file dividing means 21 of the encryption device 2, and the dummy file adding means 22 makes it necessary. depending dummy file F _D is added to, rearranged as required by rearrangement unit 23 is performed, and is sent encrypted by dividing the file encryption unit 24. The rearrangement of files may be before or after the encryption, and the file division and rearrangement, and the encryption may be performed in parallel.
[0012]
FIG. 4 is a functional block diagram of the decoding device 3.
A divided file decoding unit 31 for decoding each received divided file and a file integration unit 32 for reintegrating the decoded unit are provided.
The divided file decryption means 31 is preset with information such as an encryption method for each file on the transmission side, information such as an encryption key, and whether or not the file is an encrypted file.
The file integration unit 32 needs to know information on how to divide the file unit and information on the division position of the file unit. For this reason, for example, by determining only a mathematical expression for division and setting an initial value from the transmission side, On the receiving side, it is possible to adopt a method such as obtaining the division position sequentially by calculation based on the initial value.
Further, a file division method, an encryption method for each divided file, an encryption key, and the like may be stored in an IC card and distributed to the transmission side and the reception side. If such an IC card is used, since the information regarding encryption does not flow on the line, the confidentiality can be further maintained.
[0013]
Next, an example of the encryption / decryption processing flow will be described with reference to FIG.
The encryption process will be described below. In FIG. 5A, first, the encryption method to be used, the mathematical formula for obtaining the length of the file to be divided and subdivided, the initial value thereof, and the method for encrypting the subdivided file A formula for determining the key and its initial value, a formula for obtaining a key used for each encryption, and its initial value are set (S1). Next, the given file is divided according to the rules (S2), and is encrypted (S3). The divided individual files (hereinafter referred to as child files) are maintained in their order or rearranged according to some rules. When rearranged, an index indicating the order or the last child file is added (S4). The child file is recognized as an individual file from the outside, or the whole is recognized as one file. It is also possible to prepare a table for managing the child files and recognizing the last child file without attaching an index to the child files. In this way, it is determined whether or not the file is the last (S5), and the above processing is repeated until the last.
[0014]
Next, the decryption process will be described. In FIG. 5B, first, the index indicating the order and the last child file is deleted (S11), and each child file is decrypted using the respective conditions when encrypted. (S12), the result is output (S13), this process is repeated to the end (S14), and the files are reintegrated after the decoding process is completed to the end (S15).
[0015]
【The invention's effect】
As described above, according to the present invention, the concealability of the entire file is increased, and thus high security can be maintained. In addition, there is some restriction on the strength of the encryption method, for example, the length of the encryption key, and even when a sufficiently secure encryption method cannot be used, the entire file can be kept highly secure.
[Brief description of the drawings]
FIG. 1 is an overall view of an encryption processing system according to the present invention.
FIG. 2 is a block diagram showing functions of the encryption device 2 of the present invention.
FIG. 3 is a diagram schematically showing file division.
FIG. 4 is a functional block diagram of a decoding device.
FIG. 5 is a diagram illustrating an example of an encryption / decryption processing flow.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transmission terminal device, 2 ... Encryption apparatus, 3 ... Decryption device, 4 ... Reception terminal device, 5 ... Communication line, 21 ... File division means, 22 ... Dummy file addition means, 23 ... Rearrangement means, 24 ... Division File encryption means, 31... Divided file decryption means, 32... File integration means.

Claims (2)

Dividing means for dividing the file according to the file dividing method stored in the IC card;
An encryption method for a file stored in the IC card, an encryption means for encrypting each file divided by the dividing means with an encryption key;
Maintaining the order of each file before or after encryption of each file or rearranging, and when rearranging, rearrangement means for adding an index representing the order and the last child file,
A transmission means for transmitting each encrypted file as a separate file;
Individual files sent by the sending means, rearranged and indexed to indicate the order of each file or the last child file, and the index is deleted and divided using the encryption conditions And decrypting means for reintegrating each file after decrypting all files,
In the encryption process, a mathematical expression for determining the length of a file to be divided by the dividing means and its initial value, a mathematical expression for determining the encryption method of the subdivided file and its initial value, An encryption processing system characterized by setting an equation for obtaining a key to be used and an initial value thereof .   2. The encryption processing system according to claim 1, wherein a dummy file is further added to the divided file.

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