JPS62237834A - Data ciphering device - Google Patents

Abstract

PURPOSE:To attain the data ciphering with high reliability by providing a means operating random number data generated from a random number generator and input data. CONSTITUTION:Keys K1, K2 are inputted externally prior to the ciphering and stored in key registers 1, 2. Random number generators 3,4 generate a pseudo random number series one after another by,e.g., the congruence method according to the content of the registers 1, 2. The input data is applied with operation (g) to a random number data generated by the generator 4 and stored in order from the head of an input data buffer 5. After 256set of data are stored in the buffer 5, an address generator 6 inputs the output data just before being stored in a delay device 7 and the result of operation (f) applied to the random number data generated from the generator 3 and outputs an address in the buffer 5 for the data to be outputted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a data encryption method for the purpose of concealing information or protecting data, and in particular makes it difficult for a third party to decode or modify the data. Data Encryption Method Suitable for Improving Reliability [Prior Art] Conventionally, a method is known in which input data is divided into blocks and encrypted or decrypted using 31t, in which the positions of each block are swapped. An example of applying this method to document images is the method disclosed in Japanese Patent Laid-Open No. 59-32243.

[Problem that the invention seeks to solve]

However, in conventional methods including the above example, the replacement order itself is the encryption I! ! (hereinafter abbreviated as jp-key) or the position is swapped using the swap order determined by the key, so different input data are swapped in a fixed order.
As a result, the strength of the encryption is reduced, making it easier for a third party to decrypt or modify the data, resulting in a reduction in reliability.

Conventionally, as a method for increasing encryption strength, there is a method of encrypting using a feedback procedure, that is, a procedure that relies on human data. According to this method, the same 9? Even if different input data are encrypted, it is generally difficult to decipher because the encryption procedure is different.

However, even if we incorporate feedback,
To realize a data encryption method with sufficient cryptographic strength in cases where there is a large area with uniform brightness in the background, such as in a document image, where the input data will be similar just by changing the position. The problem remains that it is difficult to do so.

Additionally, in general, systems that incorporate feedback have the property that errors that occur for some reason in the encrypted data are propagated to the decoded data, causing the errors to expand. Conventionally, no means has been considered to be resistant to errors, that is, to reduce the influence of errors in encrypted data on decrypted data.

One object of the present invention is to eliminate the above-mentioned drawbacks and provide a more reliable data encryption method.

[Means for solving problems]

1) The purpose of increasing the encryption strength is to
By preparing a type, determining the replacement order from both the first key and input data, realizing the above feedback, and further generating random number data according to the second key, and performing calculations between the random number data and human data. achieved. Furthermore, the purpose of reducing the propagation of errors is to provide a data buffer to store the random number data, and to store the random number data using the address determined from both the first key and the input data in the same way as determining the order in which input data is exchanged. This can be achieved by specifying random number data and performing calculations on the human data after replacement.

[Effect]

By performing calculations using the random number data generated by the second key and the input data, it is possible to eliminate the apparent correlation between data located nearby in the jonin data.

By subsequently exchanging the positions, it is no longer possible to infer the input data from the encrypted data. Also, since the swapping is done depending on the input data, when two types of input data are encrypted with the same key, even data at the same position on the encrypted data is generally operated on different random number data. Therefore, it is difficult to decipher.

In addition, by storing random number data in the data buffer once and using the random number data at the specified address, even if an error occurs in the data, only the block where the error occurred and the block immediately after it will be encrypted. The decryption process must be performed using random number data different from that used in
is not done.

However, since the other blocks are correctly decoded, error propagation can be minimized by 11t.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to Figs. 1 and 2.6 Fig. 1 shows an encryption device 1 [a], in which data is encrypted manually using certain keys Kt and Kz as parameters. Output the data. The cryptographic conversion here is an operation with random number data and a swapping of the positions of input data.

Furthermore, it is assumed that human data is encrypted every 256 bytes, and the fourth block in the replacement consists of 1 byte. Of course, other combinations of the input data length and block length may be used.

First, prior to encryption, a key Kt*Kz is input from the outside and stored in key register 1 and key register 2.

Random number generator 3 and random number generator 4 generate pseudo-random number sequences one after another according to the contents of key registers 1 and 2, for example, by a congruence method.

The input data is first subjected to operation g with the random number data generated by the random number generator 4, and then stored in the input data buffer 5 in order from the beginning. Here, it is assumed that the operation g is one of possible inverse operations such as bitwise exclusive OR.

After 256 pieces of data have been stored in the manual data buffer 5, the address generator 6 performs operation f on the previous output data stored in the delay device 7 and the random number data generated by the random number generator 3. The result is input, and the address in the input data buffer 5 of the data to be output is output. However, when operating for the first time, O is assumed as the previous output data.

The output data is also input to the delay unit 7 at the same time as being output, and becomes the input to the calculation f of the next cycle.

The above operation is repeated 256 times for each block in the manual data buffer 5, and the encryption process for one input data is completed. Next, new 256-byte input data is input manually, the contents of the input data buffer 5 are updated, and then encryption processing is performed in the same manner.

For unique decoding to be possible, the address generator 6 must generate each address from O to 255 once. Next, the calculation f and the processing contents of the address generator 6 for this purpose will be explained.

First, the random number generator 3 is assumed to generate random number data r of 0.0 or more and less than 1.0, and the 1-byte output data block b is assumed to be an integer of 0 or more and 255 or less.

First, set b o = O as initialization. The operation f is the i-th
In the cycle, b + - 1 and rt are input, and f (
b+-s, rt)=mod(int(rt ・(256
-j)) +b*-t.

256-i) ajnt defined by is converted into an integer, mod (m + n)
represents the remainder when rn is divided by n. Therefore, 0≦f(
b+-ipri)≦256-i.

Address generator 6 inputs f (bt-ipri),
f from the smallest address that has not been output so far
Find the (b+-ipri)th address and output it. This process is repeated 256 times for i from 1 to 256.

In the apparatus shown in FIG. 1, the operations f, g, and the processing in the address generator 6 can be easily implemented using a normal microprocessor or dedicated hardware.

It is clear that the original input data can be restored from the encrypted data by reversing the data flow in FIG. 1 during decryption. That is, if the same key as used for encryption is input, the output of the address generator 6 will also be the same, and will be sequentially stored in the corresponding location of the input buffer 5. 256
When the storage of the input data is completed, the random number data sequentially generated by the random number generator 4 is subjected to the inverse calculation of the calculation g.

However, during decoding, the operation f is an operation on the immediately previous decoded data and random number data.

FIG. 2 shows another example of a decoding device.

The input data is encoded and encoded in 256-byte units as in Figure 1.
It is assumed that the block used as the unit of replacement consists of 1 byte.

First, prior to encryption, i3B K t and 2 are input from the outside and stored in key registers 11 and 12 . Random number generator 13 and random number generator 14 generate random number data according to the contents of key register 11 or 1.2, respectively.

In parallel with the 256-byte manual data being sequentially stored in the input data buffer 15, the random number data generated by the random number generator 14 is sequentially stored in the random number data buffer 16.

Here, the random number generator 14 randomly generates an integer between 0 and 255.

Input data buffer 15 and random number data buffer L6
When all the data is stored in the delay unit 1, as in FIG.
The immediately preceding output data outputted from 7 and the random number data generated by the random number generator 13 are subjected to a calculation f, and the result is manually input to the address generator 18. address generator 18
outputs the address of the input data buffer 15 in the same manner as the address generator 6 in FIG.

On the other hand, the result of the operation f is manually inputted as an address of the random number data buffer 16, and the random number data stored at the address is stored in the manually operated data buffer 15 by the address generator 1.
The input data stored at the output address 8 is subjected to operation g and output as encrypted data. The operation g is the first
As in the figure, 5 is an operation in which there is an inverse operation, such as exclusive OR.

The output data is also input to the delay device 17 and becomes the input for the calculation f in the next cycle.

The above process is repeated 256 times, and the encryption process for 256 bytes of manual data is completed.

In the above two examples, only one-dimensional replacement was targeted, but it goes without saying that two-dimensional replacement is easy when applied to image data, and the same effect can be obtained. .

〔Effect of the invention〕

As described above, according to the present invention, even if the input data is the same, completely different encryption processing is performed for different input data, so a more reliable encryption method can be realized. on the other hand,
Since it is possible to suppress the influence of errors that occur on encrypted data on decrypted data to a small extent, it is possible to realize an encryption system that is resistant to noise and interference.

[Brief explanation of drawings]

FIG. 1 is an apparatus configuration diagram of a first embodiment of the present invention. FIG. 2 is a diagram showing the configuration of a device according to a second embodiment.

Claims (1)

[Claims] 1. Encrypting or decoding input data by dividing input data into blocks and replacing the position of each block in an order determined by a first encryption key and input data. The device is characterized by being provided with a random number generator that generates random numbers under the control of the second encryption key, and means for performing calculations on the random number data generated by the random number generator and input data. data encryption device. 2. a data buffer for storing the random number data; a means for selecting the random number data stored in the data buffer according to an address determined by both the input data and the first encryption key; 1. The data encryption device according to item 1, further comprising means for performing arithmetic operations on the selected random number data and the input data that has been permuted in accordance with the permutation order determined by the means according to item 1.