JP2002077135A - Encrypting method, decrypting method and their equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encrypting method and a decrypting method and their equipment which enable powerful encrypting/decrypting operation wherein an ordinary sentence is not correspondent to a cipher one to one and the conventional cryptology cannot be applied by introducing error correcting encoding. SOLUTION: Error correcting encoding processing is performed to the ordinary sentence with error correcting encoding processing equipment 11. Bit errors are generated at random with random bit error generating equipment 13, to the error correcting encoded data, in a range of correction capability of error correcting code. The data in which bit errors are generated are encrypted with encrypting processing equipment 15, and the cipher is formed. The cipher is decrypted with decrypting processing equipment 21. The decrypted sentence is subjected to error correcting encoding processing with error correcting encoding processing equipment, thereby recovering the ordinary sentence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an encryption method and an encryption method for encrypting and decrypting digital data, and a device thereof.

[0002]

2. Description of the Related Art In a conventional digital data encryption technique, a plaintext is converted into a ciphertext according to a predetermined algorithm. Since this conversion is performed using the encryption key as a variable, a different ciphertext is generated for each encryption key, and the ciphertext created in this way is an encrypted encryption key (in the case of a common key method). Or another unique key associated with this key (in the case of a public key scheme). In general, if the algorithm is known, 1
It is possible to find a key by applying all keys to a pair of plaintext and ciphertext in order, but ciphers that are said to be secure are enormous in this brute force attack method. Because of the time it takes, it is virtually impossible to decipher it.

[0003] Encryption technology is essential on a network. The encryption on the network is used not only for encrypting and transmitting data such as documents, images, and voices, but also for personal authentication. The simplest method of personal authentication is by password. However, if the password is simply encrypted and transmitted, the entire data may be stolen on the network. Even if the stolen data is not decrypted, it can be used as it is and spoofed. Therefore, in the case of login authentication,
It is common to use a disposable password called a one-time password. One-time passwords include
There are a method in which the clocks are set to each other and transmission / reception is performed by performing encryption based on the current time, and a method in which encrypted passwords are sequentially generated and used sequentially.

[0004] On the other hand, in the case of commercial transactions on a network, a public key encryption such as an RSA signature is generally used for authentication. In this case, the person to be authenticated encrypts the plaintext with its own secret key and sends it, and the authenticator decrypts the plaintext using the public key. This is a method of authenticating an individual using the fact that a ciphertext that can be decrypted with a public key can be created only with a single secret key corresponding to this key.

[0005]

Since a brute force attack takes an enormous amount of time, techniques called differential cryptanalysis and linear cryptanalysis have been proposed for ciphers that are considered to be difficult to decrypt in practice. If a large number of pairs of plaintext and ciphertext can be obtained, by using these relationships, it has been possible to greatly reduce the number of brute-force attacks. On the other hand, a decryption method has been proposed in which a large number of ciphertexts are collected and a matching one is found from among them. This technique called the birthday attack method (an attack method based on the principle that even if a small number of people gather, there is a very high probability that the same birthday is present in it) is not required to collect all ciphertexts , You can find a match with a surprisingly high probability. With the rapid development of computers and the Internet, decryption by these decryption methods has become possible in a very realistic time. All of these problems arise because plaintext and ciphertext have a one-to-one correspondence via keys.

On the other hand, the simplest method of personal authentication is a password method. However, in the case of a clock system such as a one-time password system currently used, it is necessary to carry a password generator with a clock. In the case of the method of sequentially generating the password, there is a problem that the next encryption password needs to be recorded.

[0007] Further, in a system using a public key encryption such as an RSA signature, it is necessary to manage a public key very strictly at a place such as a certificate authority in order to prevent spoofing, and it is difficult to change the key in operation. There was a problem.

[0008] The present invention has been made in view of the above,
The purpose of the encryption / decryption is to introduce the error correction coding so that the plaintext and the ciphertext do not correspond one-to-one, and can perform strong encryption / decryption in which the conventional cryptanalysis cannot be applied. It is an object of the present invention to provide a method and an apparatus for chemical conversion.

[0009]

In order to achieve the above object, the present invention according to claim 1 comprises at least a document, an image,
An error correction encoding process is performed on a plaintext composed of digital data including one of a voice, a password, a fingerprint, a human phase, a vein, a retina, a voiceprint, a signature, a ciphertext, and an encryption key. A bit error is randomly generated within the range of the correction capability of the error correction code on the data subjected to the encryption process, and the data on which the bit error has occurred is subjected to an encryption process to generate a ciphertext. The point is to do.

According to the first aspect of the present invention, the plaintext is subjected to an error correction coding process, and the error correction coded data is randomly subjected to bit error correction within the range of the error correction code correction capability. And encrypt the data in which the bit error has occurred to create a ciphertext. Therefore, the plaintext and the ciphertext do not correspond one-to-one, and the ciphertext is different each time, and the conventional cryptanalysis cannot be applied. Therefore, it is possible to create a ciphertext that is extremely difficult to decipher, and it is possible to further strengthen the existing encryption method.

The present invention described in claim 2 is the same as the claim 1.
The gist is that encryption / decryption processing is performed on the ciphertext created in the described invention, error correction decoding processing is performed on the decryption text decrypted by the encryption / decryption processing, and the plaintext is restored. I do.

According to the second aspect of the present invention, the ciphertext is decrypted, the decrypted text is subjected to an error correction decoding process, and the plaintext is restored. , The ciphertext is different every time, and the conventional cryptanalysis method cannot be applied. Therefore, the cryptanalysis of the ciphertext is extremely difficult, and the existing cryptosystem can be further strengthened.

According to a third aspect of the present invention, there is provided at least a plaintext composed of digital data including one of a document, an image, a voice, a password, a fingerprint, a retina, a voiceprint, a signature, a ciphertext, and an encryption key. Error correction coding means for performing error correction coding processing on the data, and a bit error for randomly generating a bit error within the correction capability of the error correction code for the data subjected to the error correction coding processing. The gist of the present invention is to have a generating means and an encrypting means for performing an encryption process on the data in which the bit error has occurred to create a ciphertext.

According to the third aspect of the present invention, the plaintext is subjected to an error correction encoding process, and the error correction encoded data is randomly subjected to bit error correction within the range of the error correction code correction capability. And encrypt the data in which the bit error has occurred to create a ciphertext. Therefore, the plaintext and the ciphertext do not correspond one-to-one, and the ciphertext is different each time, and the conventional cryptanalysis cannot be applied. Therefore, it is possible to create a ciphertext that is extremely difficult to decipher, and it is possible to further strengthen the existing encryption method.

The present invention described in claim 4 provides the present invention according to claim 3.
Encryption / decryption means for performing encryption / decryption processing on the ciphertext created in the described invention, and error correction decoding processing on the decryption text decrypted by the encryption / decryption processing to restore the plaintext The gist of the present invention is to include an error correction decoding unit that performs

According to the fourth aspect of the present invention, the ciphertext is decrypted, the decrypted text is subjected to an error correction decoding process, and the plaintext is restored. , The ciphertext is different every time, and the conventional cryptanalysis method cannot be applied. Therefore, the cryptanalysis of the ciphertext is extremely difficult, and the existing cryptosystem can be further strengthened.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams showing the configurations of an encryption device and a decryption device according to one embodiment of the present invention, respectively.

An encryption device 1 shown in FIG. 1 includes an error correction encoding device 11 for performing an error correction encoding process on a plaintext of digital data, and an error correction encoding device 11 for performing the error correction encoding process on the data. A random bit error generation processing device 13 for randomly generating a bit error within the range of the correction capability of the error correction code, and an encryption process for performing an encryption process on the data in which the bit error has occurred to create a ciphertext It comprises a processing device 15.

The decryption apparatus 2 shown in FIG. 2 includes an encryption / decryption processing apparatus 21 for performing encryption / decryption processing on the cipher text created by the encryption apparatus 1 in FIG. Error-correction decoding device 23 that performs error-correction decoding on the decrypted text decoded in
It is composed of

The operation of the encryption device 1 and the decryption device 2 configured as described above will be described with reference to flowcharts shown in FIGS. 3 and 4, respectively.

First, the operation of the encryption device 1 shown in FIG. 1 will be described with reference to the flowchart shown in FIG.
When a plaintext is input to the error correction encoding processing device 11 of the encryption device 2, the error correction encoding processing device 11 performs an error correction encoding process on the plaintext (step S1).
Next, a bit error is randomly generated in the random bit error generation processing device 13 within the range of the error correction code correction capability for the data subjected to the error correction coding process (step S3). Then, the encryption processing device 15 performs an encryption process on the data in which the bit error has occurred to create a ciphertext (Step S).
5).

Next, the operation of the decoding device 2 shown in FIG. 2 will be described with reference to the flowchart shown in FIG.
When the ciphertext created by the encryption device 1 shown in FIG. 1 is input to the encryption / decryption processing device 21 of the decryption device 2, the encryption / decryption processing device 21 performs an encryption / decryption process on the ciphertext. Is performed (step S11). The decrypted text decrypted by the encryption / decryption processing is subjected to error correction decoding processing in the error correction decoding processing device 23, and thereby restored to a plain text (step S13). The encryption / decryption processing and the error correction / decryption processing in the encryption / decryption processing apparatus 21 and the error correction / decryption processing apparatus 23 in FIG. 2 are performed by the error encryption processing apparatus 15 and the error correction code in the encryption apparatus 1 in FIG. It corresponds to the encryption processing of the encryption processing device 11 and the encryption processing.

In the above-described embodiment, plain text includes, for example, general digital data such as documents, images, and voices, as well as passwords, fingerprints, retinas, voiceprints, signs, human faces,
Digital data for personal authentication such as hand veins (fingerprints and the like are digital data obtained by digitizing image data) and digital data such as ciphertexts and encryption keys are also included. Any method including an existing processing method may be used for the encryption processing and the error correction coding processing. Although random data may be generated using pseudo-random numbers, it is safer to use completely random data such as white noise (thermal noise). The former method is
This is very common in the software world. As the latter method, for example, a method of amplifying thermal noise and performing AD conversion (binarization) can be considered. The occurrence of a bit error is determined as follows: if the bit at the position of the data corresponding to 1 bit of the random error data (column of 0s and 1s) generated in this way (plain-text error-correction-coded) is 0, 1
Alternatively, if it is 1, it can be changed to 0. This process is easy to perform for each predetermined block. However, it is necessary to suppress the occurrence of the bit error to a level at which the plaintext can be restored by the error correction code decoding process. This method will be described later.

Conventional error correction codes such as CRC and BCH are codes for correcting bit errors on a transmission line (average bit error rate of 10 ⁻³ or less) in which the probability of occurrence of errors is extremely low. Was not conceivable. However, recently, turbo codes, high-dimensional chain codes, and the like that can be applied to worse radio transmission paths and the like have been proposed, and error correction has become possible even in a region of about 10 ⁻² to 10 ⁻¹ . These codes have error correction capabilities approaching a theoretical limit called the Shannon limit. In particular, high-dimensional chain codes (examples of references: Shinichi Kuroda et al., "Geometric decoding method and correction limit of high-dimensional hyper-dimensional chain codes", IEICE Transactions A, Vo
l. J180-A, no. 12, pp. 2145-21
54, December 1997), the number of correctable bits can be easily increased by increasing the dimension of error correction (although the number of redundant bits increases). Also, since the code is a geometric code, if the block length of the data to be error-corrected and the dimension of the error correction for the block length are determined, the number of error-correctable bit errors in one block is determined.

Therefore, when this code is applied to the present invention, the probability of occurrence of random errors is adjusted so as to be within this limit, and the number of generated random errors in one block exceeds this limit. In this case, the random error data is not used, and control such as generation of the next random data can be easily performed. Of course, a method of confirming whether error correction is possible by performing error correction decoding processing on the spot is also conceivable. If the original plaintext is not restored, the random error data is not used. If this is the case, it can be applied to all error correction coding systems. When encrypting general data,
Although the bit error rate may be low, it is desirable that the bit error rate be as high as possible when used for authentication. This is because the data for authentication is smaller than the general data, so that an increase in the number of redundant bits of the error correction code accompanying an increase in the bit error rate does not matter.

FIG. 5 is a flowchart showing an example of random bit error generation by the random bit error generation processing device 13. In FIG. 5, 0, 1
Are merely examples, and show the case where 8 bits are regarded as one block.

As shown in FIG. 5, first, for example, 8-bit "1001011" which is original data subjected to error correction coding.
"0" is a random bit error occurrence processing device 1
3 (Step S21), the random bit error occurrence processing device 13 generates random data (Step S23). The random data is generated as 8 bits, for example, "01000100" as shown in FIG.

[0028] Random bit error generation processor 13
Checks that the number of 1s in the random data is equal to or less than the correction limit of the error correction code, and
A K determination is made (step S25). In this example, the number of 1s in the random data is two. If the number of 1s in the random data is not equal to or less than the limit value, the process returns to step S21 and the generation of random data is started again. If the number of 1s is equal to or less than the limit value, a bit error is generated in the original text (step S21). S27). The process of generating a bit error in the original text is performed by inverting the original text data at one location of the random data as shown in step S27, that is, when the original text data at one location of the random data is one. In this case, this 1 is set to 0, and when the original sentence data is 0, this 0 is set to 1. For example, as described above, random data is set to “01000100” for “10010100” of the original sentence. , "110
10010 ", and output as an error superimposed sentence (step S29).

Next, an example of encryption / decryption of authentication data at the time of personal authentication will be described with reference to flowcharts shown in FIGS. In both figures, the place described as the password may be any digital data for personal authentication, such as a fingerprint, a retina, a voiceprint, and a signature. In this example, a case is shown in which the accumulated amount of past data is reduced using time information.

First, the encryption of the personal authentication data will be described with reference to FIG. When the user name and the password are input, an expiration date is added to the user name and the password, and the error correction encoding device 11 performs an error correction encoding process (steps S31 and S33). Note that the expiration date may be set to a time slightly earlier than the current time in consideration of a difference in the clock with the authentication side.

Then, a bit error is generated by the random bit error generation processor 13 with respect to the data subjected to the error correction coding processing (step S35).
The data in which the bit error has occurred is subjected to encryption processing by the encryption processing device 15 to create a ciphertext (step S37).

Next, the decryption of the personal authentication data will be described with reference to FIG. Upon receiving the ciphertext created by the encryption processing device 15, the ciphertext is subjected to encryption / decryption processing by the encryption / decryption processing device (step S51).
Then, the data that has been subjected to the decryption processing is checked for the same data in the past,
Prevent intrusion of impersonation (step S53). The check of the past data may be performed before the encryption / decryption processing.

As a result of checking the past data, if there is no same in the past data, the error correction decoding processing device 2
3 is subjected to error correction decoding processing (step S55),
Then, the expiration date is checked (step S5).
7). As a result of the expiration date check, if it is within the expiration date, this data is registered as past data (step S59), and the user name and password restored by the error correction decoding process are output (step S6).
1), handed over to the certifier. The data registered as the past data is the ciphertext itself when the past data check is performed before the decryption process, and when the past data check is performed after the decryption process. , Data after decryption.

The past data may be discarded from the one whose expiration date has expired. This personal authentication is extremely simple compared to the conventional method. In addition, it can be used not only for business transactions on a network but also for various transactions that do not involve the transfer of money.

As described above, in the encryption / decryption method of the present invention, since a random bit error is added on the way, a different encrypted text is generated every time even if the same plain text is encrypted. Therefore, there is no one-to-one correspondence between the plaintext and the ciphertext. Therefore, even if a large number of pairs of plaintext and ciphertext are obtained, the relevance cannot be extracted, and the number of brute force attacks by differential cryptanalysis or linear cryptanalysis cannot be reduced. Therefore, in order to decrypt this cipher, an exhaustive attack is required, and it takes an enormous amount of time, making it practically difficult to find a key. Of course, even if the same plaintext is encrypted, a different ciphertext is generated every time, so that the birthday attack method cannot be applied.

On the other hand, when a bit error is randomly generated for data on which an error correction encoding process has been performed on a password, and then the encrypted data is transmitted after being generated, a different encrypted password is generated each time. Therefore, on the authentication side, simply excluding access with the same password,
It is possible to prevent intrusion by impersonation. If the password is not an encryption password used in the past, the password can be taken out by decrypting and performing error correction decryption.

Further, when the present invention is used for authentication of commercial transactions, etc., a bit error is generated at random on the side to be authenticated after error correction encoding of the password. In the same manner as described above, the data can be transmitted after being encrypted with the public key of the partner (authentication side). The authenticating side decrypts the message with its own private key. At this time, it is checked that the same data has not been authenticated in the past. This method does not require the use of a key to be authenticated, and is extremely simple to operate. Of course, it is also possible to use the conventional authentication method to enhance the security of the conventional method by replacing only the encryption processing with the method of the present invention. As long as it can identify an individual, anything other than a password can be used, and various digital data such as a fingerprint, a retina, a voiceprint, and a signature can be applied.

When the present invention is used for personal authentication, it is necessary to check that the same data has not been authenticated in the past, as described above. The expired data can be deleted from the past data, and the problem that the storage capacity of the past data increases with the number of uses is eliminated.

As an encryption technique, a technique for further encrypting the encrypted data is also used. For example, a method called triple DES is a cipher whose security is further improved by passing a standardized encryption algorithm called DES three times. The method and the apparatus of the present invention are characterized in that error correction coding and random bit error generation are performed before encryption, and it is of course possible to use the method repeatedly several times. Also, when data encrypted by common key encryption is sent, a method of encrypting the common key itself with a public key and transmitting the data is usually used. In this case, the present invention can of course be applied. is there. That is, what is described as plaintext in the present invention may be any digital data, and may be ciphertext or an encryption key.

[0040]

As described above, according to the present invention,
An error correction encoding process is performed on the plain text, a bit error is generated in the error correction encoded data, and the data in which the bit error has occurred is encrypted to create a ciphertext. Not corresponding to 1, the ciphertext is different every time, and even if you obtain many pairs of plaintext and ciphertext, it takes brute force attacks to find the key, and it takes an enormous amount of time to actually find the key Is difficult, and the existing encryption method is further strengthened.

When the encryption method and the decryption method of the present invention and their devices are used for personal authentication, an authentication system can be configured and operated very easily as compared with conventional one-time password and RSA authentication methods. be able to. Of course, it is also possible to replace the encryption processing of the conventional authentication method with the method of the present invention to enhance the security of the conventional method.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an encryption device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a decoding device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of the encryption device shown in FIG. 1;

FIG. 4 is a flowchart showing an operation of the decoding device shown in FIG. 2;

FIG. 5 is a flowchart showing an example of random bit error generation by a random bit error generation processing device used in the encryption device shown in FIG. 1;

FIG. 6 is a flowchart showing an example of encryption of authentication data at the time of personal authentication in the embodiment shown in FIGS. 1 and 2;

FIG. 7 is a flowchart showing an example of decryption of authentication data at the time of personal authentication in the embodiment shown in FIGS. 1 and 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 encryption device 2 decryption device 11 error correction encoding processing device 13 random bit error generation processing device 15 encryption processing device 21 encryption decryption processing device 23 error correction decoding processing device

Claims (4)

[Claims] At least, at least, a document, an image, a voice, a password, a fingerprint, a human phase, a vein, a retina, a voiceprint, a signature, a ciphertext,
And performing an error correction encoding process on a plain text composed of digital data including one of the encryption keys, and within the range of the error correction code correction capability for the data subjected to the error correction encoding process. The method according to claim 1, wherein a bit error is generated at random, and an encryption process is performed on the data in which the bit error has occurred to create a ciphertext. 2. An encryption / decryption process is performed on the encrypted text created by the encryption method according to claim 1, and an error correction decryption process is performed on the decrypted text decrypted by the encryption / decryption process. And restoring the plaintext. 3. At least, a document, an image, a voice, a password, a fingerprint, a human phase, a vein, a retina, a voiceprint, a signature, a ciphertext,
Error correction coding means for performing error correction coding processing on a plaintext composed of digital data including one of the following and an encryption key; and the error correction coding means for performing the error correction coding processing on the data. Bit error generating means for randomly generating a bit error within the range of the correction capability of the above, and encryption means for performing an encryption process on the data in which the bit error has occurred to create a ciphertext. Characteristic encryption device. 4. An encryption / decryption means for performing encryption / decryption processing on an encrypted text created by the encryption apparatus according to claim 3, and an error correction for the decrypted text decrypted by the encryption / decryption processing. An decoding device comprising: an error correction decoding unit that performs a decoding process to restore a plaintext.