JP2008185616A - Secret key ciphering method, secret key ciphering device and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secret key ciphering method or the like of a ciphering encode system high in cipher strength irrespective of relatively low processing, which can be mounted on equipment incorporated with a low-performance CPU, a server apparatus for ciphering large amounts of data at once or the like. <P>SOLUTION: The secret key ciphering method of performing ciphering processing by using a secret key comprises: a secret key producing step of producing the secret key by using a hash function (MD5 algorithm); and a ciphering step of performing an exclusive OR operation (XOR operation) by the use of the secret key produced by the secret key producing step and, thereby, performing the ciphering. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to digital data encryption.

  Conventionally, various encryption methods such as a secret key encryption method and a public key encryption method have been proposed as digital encryption techniques. As these encryption methods, for example, Triple DES, DEAL, IDEA, elliptic curve encryption, ElGamal encryption, and the like exist. In addition, these encryption methods are widely used for communication via networks and digital data encryption, and are widely used techniques for improving the security in the digital data society.

  A feature of these encryption methods is that the encryption strength is very high. It is very good considering the point of being secure, but the complexity of the algorithm and the computation are enormous, and depending on the platform, there are cases where it is difficult to implement. For example, this is the case where the CPU's computing power such as an embedded device cannot be expected so much. In such a case, it is better to give priority to high-speed processing instead of slightly reducing the encryption strength.

  Furthermore, as another example, even when encryption is performed by a server machine equipped with a high-speed CPU, even when a large amount of data needs to be encrypted instantaneously, the time required for the encryption processing is also the same. I can't call. Therefore, as in the example of the embedded device, it is necessary to give priority to the high speed of processing instead of slightly reducing the encryption strength.

  As described above, when encryption processing is performed in accordance with the conventional encryption method, although the encryption strength is high, an adverse effect due to an increase in processing time is a serious problem. On the other hand, if the encryption strength is low, there is a possibility that a new problem that the security cannot be maintained may occur.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a secret key encryption method of an encryption encoding method having a high encryption strength in spite of relatively low processing. It is another object of the present invention to provide an encryption method that ensures encryption strength and to solve the above-described problems.

  The present invention is a secret key encryption method for performing an encryption process using a secret key, a secret key generation step for generating a secret key using a hash function, and a secret key generated by the secret key generation step. And an encryption step for performing an encryption process by performing an exclusive OR operation using the same.

  According to the present invention, it is possible to perform secret key encryption that makes it difficult to specify a secret key by a simple and low-load secret key encryption method. That is, it is possible to perform a secret key encryption process with a lower load and higher speed than the conventional encryption methods such as Triple DES, DEAL, IDEA, elliptic curve encryption, and ElGamal encryption. Therefore, it can be mounted on a low-performance CPU embedded device or a server device that encrypts a large amount of data at one time.

  In the present embodiment, a secret key is generated by a secret key generation unit that generates a secret key using a hash function, and then the data is encrypted, thereby providing an encryption method with a low processing amount and high encryption strength. be able to. Here, the hash function is a calculation method for generating a fixed-length pseudo-random number from a given original text, and the generated value is called a “hash value”. In the present embodiment, the hash function is described as MD5 (abbreviation for Message Digest 5).

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a functional configuration of a secret key encryption apparatus according to the present embodiment.
Reference numeral 101 denotes a secret key generation unit using MD5, which generates a secret key 2 (105) from a secret key 1 (104). The secret key 1 is a character string code having an arbitrary length and may have any length. The hash value of the secret key 1 is calculated by the secret key generation unit 101 using MD5. As this hash value, a 128-bit message digest value is obtained based on the MD5 specification. This message digest value, which is a hash value, is set as the secret key 2 (105). When the generation of the secret key 2 is completed, the process of the secret key generation means 101 by the MD 5 is completed.

  Reference numeral 102 denotes encryption means by XOR processing, which performs actual encryption processing. Here, the XOR process is an exclusive OR operation and is also expressed as an XOR operation. The encryption means 102 by XOR processing performs encryption processing using the secret key 2 (105) generated by the MD5 secret key generation means 101. First, the encryption means 102 by the XOR process reads the encryption original data 107 that is the original data necessary for the encryption process, performs the encryption process using a secret key encryption method, and converts the generated data into the encrypted data 108. As output. Reference numeral 103 denotes secret key update means, which updates the secret key in accordance with the unit of encryption processing. Specifically, each time the secret key encryption process is performed 1 byte, the secret key 2 is updated and held as secret key 2 update information 106.

FIG. 2 is a diagram illustrating an example of a secret key used in the present embodiment.
Reference numeral 201 denotes the secret key 1. The secret key 1 is a secret key that is determined by the person who performs the encryption process. The secret key 1 is allowed to be an arbitrary length character string. In FIG. 2, the character string “Flower of SunFlower” is used as the secret key 1. Since the encryption method according to the present embodiment is based on the secret key encryption method, this secret key needs to be known by the person who performs the encryption encoding process and the person who performs the encryption decoding process. The secret key 1 may be an arbitrary-length character string, and may be arbitrary-length binary data.

  Reference numeral 202 denotes the secret key 2. The secret key 2 is a hash value calculated by the MD5 algorithm. Therefore, as shown in FIG. 2, the secret key 2 is binary data of 16 bytes. That is, the encryption method of the present embodiment is a 128-bit length encryption method. However, it is also possible to use only 64 bits of the hash value calculated by the MD5 algorithm as the secret key. Therefore, it is possible to select an arbitrary length of encryption strength.

FIG. 3 is a diagram showing a flowchart of the secret key encryption process according to the present embodiment.
This flowchart shows the details of the processing flow of the secret key generation means 101 by MD5, the encryption means 102 by XOR processing, and the secret key update means 103. Before executing this flowchart, it is necessary to prepare data for performing the secret key encryption process and the secret key 1 respectively. These values are data recorded by the private key 1 information holding 104 and the encryption source data holding 107 described above.

  First, the encryption process starts from step S301. The following is performed by the CPU of the computer, for example. When the secret key 1 is input in step S302, the secret key 1 is read. This value is stored in the above-described secret key 1 information holding 104, and is performed by reading this value.

  Next, in step S303, the secret key 2 is calculated from the secret key 1 using the MD5 algorithm. This value is held in the private key 2 information holding 105. The secret key 2 is a hash value based on the MD5 algorithm, and it is almost impossible to calculate the secret key 2 from the hash value. Therefore, by not using the secret key 1 itself for the encryption process, the possibility of the secret key 1 being taken by a third party by decryption is reduced.

  Next, in step S304, a pointer pointing to the encryption source data is initialized. The encryption source data is stored in the encryption source data storage 107 and is very large data. For this reason, since it is difficult to perform encryption processing on all data at once, the pointer is initialized for the purpose of sequentially performing encryption processing on the data held in the encryption source data using the pointer.

  Next, in step S305, a pointer pointing to the encrypted data is initialized. The encrypted data is stored in the encrypted data storage 108 and is very large data. For this reason, data is managed by pointers in the same way as encryption source data. The data stored in the encrypted data is also initialized with a pointer in order to perform the encryption process sequentially in the same manner as the encryption source data. The process corresponding to the initialization of the secret key encryption process is completed by the processes in steps S301 to S305.

Next, steps S306 to S314 are processes for actually performing private key encryption.
In step S306, the encryption source data 1 byte is copied from the pointer indicating the encryption source data to the buffer. By this process, the encryption source data is called by 1 byte, and is set as a secret key encryption target. The buffer here refers to a specific memory or register, and may be any medium that can hold 1 byte of data.

  In step S307, XOR processing is performed for the number of bytes of secret key 2 (16 bytes). In step S308, it is determined whether or not XOR processing has been performed on all 16-bytes of the secret key 2. If all 16 bytes have not been XOR processed, the processing from step S307 to S308 is repeated. Encryption processing is performed by this XOR processing. The encryption strength is 16 bytes (128 bits), but this may be performed by changing the length to an arbitrary length. In particular, in this embodiment, it is 16 bytes.

  Next, in step S309, the value obtained by performing the secret key encryption is output to the pointer indicating the encrypted data. Thus, the encryption process for 1 byte is completed.

The secret key 2 is updated by the following process.
In step S310, the encrypted data is added to all 16 bytes of the secret key 2. The secret key thus obtained is held as secret key 2 update information 106. In addition, the value obtained in step S310 is used as the secret key 2 in the process of step S307 described above. That is, the secret key 2 is updated using the encrypted data that has been encrypted. In this way, the encryption strength is increased by constantly updating the secret key 2.

  After the private key encryption processing is performed for 1 byte, both the pointer indicating the encryption source data and the pointer indicating the encryption data are incremented in steps S311 and S312, and the next encryption source data is prepared for secret key encryption. do.

  Next, in step S313, it is determined whether or not the encryption processing has been performed on all the encryption source data. If it is still halfway, the process returns to step S306 and the private key encryption processing is performed again. If all the encryption processes have been completed, the encryption process ends in step S314. As a final result, the data subjected to the secret key encryption process remains in the encrypted data holding 108, and this becomes output data.

  In this secret key cryptosystem, a secret key 2 is newly generated by MD5, thereby making it possible to make the secret key actually used in the secret key encryption process more complicated. However, the actual calculation uses the MD5 algorithm and is relatively light in processing.

  In addition, the secret key cipher process itself includes only an exclusive OR operation, which is an XOR process, an addition operation for updating the secret key, and a pointer increment. For this reason, it does not include floating-point arithmetic and the like, is composed only of integer arithmetic or logical arithmetic, is extremely light processing, and can be easily implemented on any CPU.

  Although the encryption process, that is, the encoding process has been described with reference to FIG. 3, the same flowchart can be used for the decryption process. Therefore, the secret key 1 required for the decryption process is exactly the same as the secret key 1 used in the encryption process, and the encrypted data is used as the encryption source data. The encrypted data is decrypted. Finally, the decrypted data is output to the encrypted data holding unit 108, and the decrypted data can be obtained.

  As described above, according to the present embodiment, it is possible to perform a secret key encryption process with a high encryption strength despite a low load.

  Each step of the secret key encryption method and each means constituting the secret key encryption apparatus in the embodiment of the present invention described above can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium recording the program are included in the present invention.

  In addition, the present invention can be implemented as, for example, a system, apparatus, method, program, or recording medium. Specifically, the present invention may be applied to a system including a plurality of devices.

  Note that the present invention supplies a software program that implements the functions of the above-described embodiments directly or remotely to a system or apparatus. This includes the case where the computer of the system or apparatus also reads, executes, and controls the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention. In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. Furthermore, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.

  As another method, the program read from the recording medium is first written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of the program, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

It is a figure which shows the structure of the private key encryption apparatus which concerns on this embodiment. It is a figure for demonstrating the private key which concerns on this embodiment. It is a figure which shows the flowchart of the encryption process which concerns on this embodiment.

Explanation of symbols

101 Secret key generation means by MD5 102 Encryption means by XOR processing 103 Secret key update means 104 Private key 1 information 105 Private key 2 information 106 Private key 2 update information 107 Encryption source data 108 Encrypted data 201 Private key 1
202 Private key 2

Claims (7)

A secret key encryption method for performing encryption processing using a secret key,
A secret key generation step of generating a secret key using a hash function;
A secret key encryption method comprising: an encryption step of performing an encryption process by performing an exclusive OR operation using the secret key generated by the secret key generation step.   2. The secret key encryption method according to claim 1, further comprising a secret key update step of updating the secret key according to a unit of the encryption process.   3. The secret key encryption method according to claim 2, wherein in the secret key update step, the secret key is updated using the encrypted data encrypted in the encryption step.   4. The secret key encryption method according to claim 1, wherein a length of the secret key can be arbitrarily changed.   The secret key encryption method according to any one of claims 1 to 4, wherein the hash function is MD5 (Message Digest 5). A secret key encryption device that performs encryption using a secret key,
A secret key generating means for generating a secret key using a hash function;
A secret key encryption apparatus comprising: encryption means for performing encryption processing by performing an exclusive OR operation using the secret key generated by the secret key generation means. A computer program for controlling a secret key encryption device that performs an encryption process using a secret key,
A secret key generation step of generating a secret key using a hash function;
A computer program for causing a computer to execute an encryption step of performing an encryption process by performing an exclusive OR operation using the secret key generated by the secret key generation step.

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