JP2864813B2 - Encryption device and decryption device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption device and a decryption device used in a communication system or a computer system.

[0002]

2. Description of the Related Art In a communication system or a computer system, in order to prevent an unauthorized person from illegally acquiring information, the information is converted into encryption (encryption) and the information is restored (decrypted) to the original information. In short, this encryption / decryption method is based on the input “information to be encrypted (original information)” or “encrypted information (encryption)”. In this method, a predetermined operation is performed, and the remainder obtained by dividing the operation result by a predetermined numerical value is used as “encryption” or “original information”.

[0003] As a typical encryption / decryption method of this kind, there is an RSA method that is widely known and used.
This was proposed by Rivest, Shamir and Edelman in 1978 (RLRivest, A. Shamirand
L. Addleman, “A Method for Obtaining Digital Signat
ures and Public-key Cryptosystems, ”Comm.ACM, Vo
l.21, No.2, pp.120-126, 1978), and the RSA method is named after the initials of the proposer. As for the RSA method, for example, a book “Theory of Information and Code” (Miyagawa,
Harashima and Imai co-authored, published by Iwanami Shoten, 1983)
There is a simple commentary in the chapter.

According to the above-mentioned document, an encryption device and a decryption device based on a general encryption / decryption method including the RSA method include:
In addition to encrypting the information in a way that prevents unauthorized persons from prying out the information, it also prevents the sender of the information from defrauding that information was later transmitted, and preventing fraud, It can also be used to prevent unauthorized persons from pretending to be authorized persons and sending out false information, but for the sake of convenience in the following description, unauthorized persons will snoop on information. A case in which information is encrypted for the purpose of preventing the situation will be described using the RSA method as an example.

[0005] In the encryption / decryption method in the RSA method,
A numerical value e is prepared as an encryption key, a numerical value d is prepared as a decryption key, and a numerical value N is prepared in advance as a common key for encryption and decryption. These numerical values (e, d, N) are integers and are determined by the method described in detail in the book. Further, the numerical expression P of the information to be encrypted is obtained by dividing the information represented by the bit sequence of “1” and “0” into bit strings of a finite length. Therefore, in the following description, "information" and "numerical representation of information" are not distinguished unless there is confusion.

The encryption is performed by an operation of dividing the information P raised to the power e by N and obtaining the remainder C as the encryption C, as shown in the following Expression 1.

[0007]

## EQU1 ## C = P ^e mod N

[0008] Further, as shown in the following equation (2), the value obtained by raising the cipher C encrypted as described above to the power d is N
, And restoring the remainder P as the original information P.

[0009]

P = C ^d mod N

[0010]

As described above, the encryption / decryption method, that is, when a predetermined operation is performed on inputted information P and the operation result is divided by a predetermined numerical value N In the scheme in which the remainder is used as encryption or original information, the remainder is calculated when the remainder is divided by the common key N in the encryption process.
It is necessary to be able to distinguish it from other information. However, although the common key N is an arbitrary integer, it cannot be a convenient power of two. In communications and computers,
The binary system is used.

Therefore, in the conventional encryption / decryption method,
The information P is set to a value smaller than the common key N so that the above distinction can be made. Further, since the common key N does not have a convenient power of 2, the information P may have a larger value than the common key N if the information P and the common key N have the same bit length. Therefore, normally, the information to be encrypted is divided and formed so that the bit length of the information P is shorter by one bit than the bit length of the common key N.

[0012] Then, since the bit length of the encryption is the same as the bit length of the common key N, the encryption becomes one bit longer than the information, and there is a problem that the information transmission efficiency and the storage efficiency deteriorate.

An object of the present invention, model improves transmission efficiency and the storage efficiency of information, and to provide an encryption apparatus that give improved confidentiality degree of encryption and decryption apparatus.

[0014]

In order to achieve the above object, an encryption device and a decryption device according to the present invention have the following configurations. That is, the encryption device of the first invention uses the input information
A predetermined operation is performed on the
Output the remainder divided by the given numerical value N and use it as encryption
A code converter for performing a predetermined code conversion on input information in an output encryption device ;
A predetermined value N is applied to the output X of the code converter.
An encryption circuit for performing a predetermined arithmetic operation and performing an encryption process; a comparator for comparing a magnitude relationship between a value X of the output of the code converter and a predetermined numerical value N ;
X is equal to N or N depending on the comparison result of the comparator .
If it is larger, select the output X of the code converter
If X is smaller than N , the output of the encryption circuit
And a selector for selecting and outputting as encryption information for the input information.

The decoding apparatus of the second invention, the input encryption
To perform a predetermined operation and give the operation result in advance.
Output the remainder divided by the given number N and support the input encryption
In a decryption device that restores and outputs plaintext information
For the input information , the numerical value N given in advance is modulo
A decoding circuit that performs a predetermined operation to perform a decoding process; a comparator that compares a magnitude relationship between the value Y of the input information and a predetermined value N ; a comparison between the comparators Y is equal to or greater than N depending on the result
Is selected, the value Y of the input information is selected, and Y is N
A switch for selecting and outputting the output of the decoding circuit if smaller than ; a reverse code for performing a predetermined reverse code conversion on the output of the switch and outputting it as decoded information for the input information And a converter.

According to a third aspect of the present invention, there is provided an encryption device for inputting information.
To perform a predetermined operation and give the operation result in advance.
Output the remainder divided by the given number N and output it as a cipher
A first switch that first selects and outputs input original information and then selectively outputs information that has undergone a predetermined encryption process in accordance with a control signal given from the outside; and code converter which outputs subjected to predetermined code conversion to the output; the output X of the code converter, a modulo value N previously given
An encryption circuit that performs a predetermined operation to perform an encryption process; a comparator that compares a magnitude relationship between an output value X of the code converter and a predetermined numerical value N ; Depending on the result of the comparison , X is equal to or greater than N
If it is large, select the output X of the code converter ,
If X is smaller than N, select the output of the encryption circuit.
-Option and again enter the selected output encrypted information as each information said predetermined encryption process has been performed on the first switch
The operation of supplying the data as force information and encrypting it
And a second switch that enables the return .

The decoding apparatus of the fourth invention, the input encryption
To perform a predetermined operation and give the operation result in advance.
Output the remainder divided by the given number N and support the input encryption
In a decryption device that restores and outputs plaintext information
According to a control signal given from the outside, first, the input original information is selected and output, and then the information which has been subjected to a predetermined decryption process is selectively output and decrypted again as the input encryption.
A first switch that enables the operation to be repeated a predetermined plurality of times ; and a predetermined output provided from the first switch .
A decoding circuit for performing a predetermined arithmetic operation modulo a numerical value N to perform a decoding process; and a value Y of an output of the first switcher
And a comparator for comparing the magnitude relationship between the value and a predetermined numerical value N ; and Y is equal to N according to the comparison result of the comparator.
Is greater than N, the output Y of the first switch is
And if Y is smaller than N, the decoding circuit
The second switching unit and for selectively outputting an output; the second said subjecting it to predetermined inverse code conversion on the output of the switching device and outputs as information made a of the fixed decoding process first
A predetermined number of decoding operations while supplying the data to the switch;
It is characterized in further comprising a; a possibly tighten that inverse code converter.

According to a fifth aspect of the present invention, there is provided the encryption device according to the first or third aspect of the invention, wherein the code converter outputs the input numerical value in a form in which the most significant bit is inverted. It is assumed that.

A decoding device according to a sixth aspect of the present invention is the decoding device according to the second or fourth aspect of the invention; wherein the inverse code converter outputs the input numerical value with its most significant bit inverted. It is a feature.

The encryption device of the seventh invention is the encryption device of the first invention or the third invention; the code converter is a negation circuit for inverting the most significant bit in the input numerical value;
A circuit for converting a numerical value consisting of a plurality of low-order bits in the input numerical value into a numerical value consisting of a predetermined bit length; and a plurality of high-order bits excluding the most significant bit in the input numerical value, the same as the predetermined bit length. An exclusive-OR circuit for performing an exclusive-OR operation on a numerical value consisting of a plurality of upper bits of a bit length and the numerical value consisting of the predetermined bit length; and an output of the NOT circuit and an output of the exclusive OR circuit. The plurality of lower-order bits and the remaining bits in the input numerical value are output from the code converter.

The decoding device according to an eighth aspect of the present invention is the decoding device according to the second or fourth aspect of the present invention; the inverse code converter includes a NOT circuit for inverting the most significant bit in the input numerical value; A circuit for converting a numerical value consisting of a plurality of lower bits in a numerical value into a numerical value consisting of a predetermined bit length; and a plurality of upper bits excluding the most significant bit in the input numerical value and having the same bit length as the predetermined bit length An exclusive-OR circuit for performing an exclusive-OR operation on a numerical value consisting of a plurality of upper bits and a numerical value consisting of the predetermined bit length, wherein the output of the NOT circuit, the output of the exclusive OR circuit, The lower bits and the remaining bits in the input numerical value are output from the inverse code converter.

[0022]

Next, the operation of the encryption device and the decryption device of the present invention configured as described above will be described. Note that the encryption device and the decryption device of the present invention are intended to prevent unauthorized persons from prying information, and to defraud that the person who transmitted the information denied that the information was transmitted later. It can be applied for both the purpose of preventing work and the purpose of preventing unauthorized persons from pretending to be authorized persons and transmitting false information. For the purpose of preventing anyone who does not peep into the information, the following is an example.

In the encryption device of the first invention, a predetermined code conversion is performed on the input information to be encrypted (P for convenience). If the numerical value A obtained by the code conversion is smaller than a predetermined numerical value (corresponding to the common key N), the encryption is performed by the conventional encryption method (a known encryption method that is not limited to the above-described formula 1). If the numerical value A is not smaller than the common key N, the numerical value A is directly output as the encryption.

Here, in the comparator, the numerical value A and the common key N
The information P to be encrypted has the same bit length as the common key N. The encryption method according to the present invention is not limited to the RSA method. However, if one property of the RSA method, that is, the key (e, d, N) is skillfully selected, information having a value smaller than the common key N can be obtained. Focusing on the property of being able to correspond one-to-one with encryption, and processing as described above,
Since all information and the encryption that are not longer than the effective key length than the common key N can correspond to each other on a one-to-one basis, encryption can be performed so that the bit length of the encryption C is not longer than the bit length of the information P. That is, information transmission efficiency and storage efficiency can be improved.

Further, in the decryption device of the second invention, the cipher obtained as described above (referred to as C for convenience) is obtained by a conventional decryption method (a known decryption method which is not limited to Expression 2). In parallel with the restoration, the magnitude relationship between the cipher C and the common key N is compared. If the cipher C is smaller than the common key N, the restored numerical B
If not smaller, the code C is subjected to the reverse code conversion of the code conversion, and is used as restoration information.

Then, the encryption device of the third invention firstly performs the encryption of the first invention on the information P, and then uses the encryption obtained in this way as new information P 'and adds it to the encryption of the first invention. This is repeated a predetermined number of times to obtain a desired cipher. In the decoding device of the fourth invention,
Decoding is performed in a similar manner. Encryption of the first and second inventions
The decryption method is effective for applications where confidentiality is not sufficient.

The code converter and the inverse code converter "output the input numerical value in a form in which the most significant bit is inverted" in order to make the input and the output correspond one-to-one.
As described above (fifth and sixth inventions), or "the most significant bit in the input numerical value is inverted, the plural lower bits in the input numerical value, and the plural lower bits are included. Exclusive of a value obtained by converting a numerical value into a numerical value having a predetermined bit length and a numerical value including plural high-order bits having the same bit length as the predetermined bit length except for the most significant bit in the input numerical value. (7th and 8th inventions) are configured to output the result obtained by performing a logical sum and the remaining bits in the input numerical value.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an encryption device according to a first embodiment of the present invention. This encryption device comprises a code converter 11 and a comparator 1
2, an encryption circuit 13 and a switch 14.

In FIG. 1, a code converter 11 performs a predetermined code conversion on the information to be encrypted (the above-described information P) input from the input terminal 10 and compares the result with the comparator 12. Output to the conversion circuit 13 and the switch 14.

The comparator 12 compares the value of the output information of the code converter 11 (hereinafter, A) with a predetermined numerical value (the above-mentioned common key N), and finds that the numerical value A is the common key. If it is smaller than N, "1" is given to the switch 14 as a control signal, and if the numerical value A is not smaller than the common key N, "0" is given to the switch 14.

On the other hand, the encryption circuit 13 includes the code converter 1
1 is subjected to a predetermined encryption by a conventionally known method, and the result is supplied to the switch 14.

As a result, the switch 14 selects the output of the encryption circuit 13 if the output of the comparator 12 is "1", and conversely, if the output of the comparator 12 is "0", the code converter 11
And outputs it from the output terminal 15 as encryption. When the output of the code converter 11 is output as a cipher, there is no problem because the output is extremely small.

FIG. 2 shows a decoding apparatus according to a second embodiment of the present invention. This decoding device basically includes a comparator 22, a decoding circuit 23, a switch 24, and an inverse code converter 21.

In FIG. 2, the encrypted information input from the input terminal 25, that is, the encryption is transmitted to the comparator 22.
And a decoding circuit 23 and a switch 24. The comparator 22 compares the magnitude of the inputted cipher value with a predetermined numerical value (common key N), and inputs “1” if the inputted cipher value is smaller than the common key N. If the encrypted value is not smaller than the common key N, "0" is given to the switch 24 as a control signal.

On the other hand, the decryption circuit 23 performs a predetermined decryption on the inputted cipher by a conventionally known method, and supplies the result to the switch 24.

As a result, the switch 24 selects the output of the decoding circuit 23 if the output of the comparator 22 is "1", and conversely, the input terminal 25 if the output of the comparator 22 is "0". And outputs it to the inverse transcoder 21.

The reverse code converter 21 is provided with a switch 2
4 is subjected to code conversion reverse to that of the code converter 11, and is output from the output terminal 20 as restoration information for the encryption supplied from the input terminal 25. That is, the inverse code converter 21 has the same configuration as the code converter 11.

FIG. 3 shows an encryption device according to a third embodiment of the present invention. This encryption device is the same as the device of the first embodiment, except that the (first) switch 31 is connected to the code converter 11.
It is preceded by Hereinafter, description will be made focusing on the portion according to the third embodiment.

In FIG. 3, the switch 31 has an input terminal 1
0 to be encrypted and (second) switch 14
And selects one of the two inputs in accordance with a control signal 30 from the outside, and outputs it to the code converter 11.
Give to.

More specifically, the control signal 30 becomes, for example, "1" at the timing when the information to be encrypted is input from the input terminal 10, and causes the switch 31 to selectively output the information to be encrypted from the input terminal 10. Then, it becomes "0" at the timing when the switch 14 outputs, and the switch 31 is connected to the switch 31.
4 is selected, and thereafter, the state of "0" is maintained until the switch 14 outputs a predetermined number of times, and then becomes "1" when new information to be encrypted is input. is there.

In short, the device of the third embodiment is a device that performs a plurality of encryption processes on each piece of information to be encrypted and outputs the final value of each of the plurality of times as a code, thereby enabling sufficient confidentiality to be maintained. Is what you do. The decryption device for the encryption device according to the third embodiment is configured as shown in FIG.

That is, in FIG. 4, the device of the fourth embodiment has a (first) switch 41 connected to the input stage of the device of the second embodiment.
Is preceded by The switch 41 is a switch.
Similarly, according to the control signal 40 given from the outside,
One of the information to be decoded input from the input terminal 25 and the output of the inverse code converter 21 is selected, and the selected information is supplied to the comparator 22, the decoding circuit 23, and the (second) switch 24. Since the control signal 40 is the same signal as the control signal 30, the value of the last of a plurality of decoding processes is output as restoration information.

Next, the code converter and the inverse code converter will be described. Since these have the same configuration, they will be simply referred to as “converters” below. This converter has a configuration in which an input and an output correspond to each other on a one-to-one basis. In this embodiment, the following two configurations are employed.

The first configuration is such that "the input numerical value is output with its most significant bit inverted". When the most significant bit is inverted, a numerical value larger than the common key N is always converted to a numerical value smaller than the common key N.
Therefore, in the device of the third embodiment, when encryption is repeatedly performed using the code converter 11 having such a configuration, the switching unit 14 sets the encryption circuit 1 in the j-th iteration.
Even if the output of the input terminal 3 is not selected, the output of the encryption circuit 13 is always selected in the (j + 1) th repetition.
The information to be encrypted input from 0 is encrypted at least once by the encryption circuit 13. Therefore, the risk of decryption by a third party is reduced.

FIG. 5 shows the second configuration.
In FIG. 5, assuming that the numerical value input from input terminal 50 is L bits, this converter includes a NOT circuit 51 for inverting one bit of the most significant bit in the input numerical value, A hash function unit 53 for converting a numerical value consisting of lower a bits into a numerical value consisting of b bits, and a numerical value consisting of b bits output from the hash function unit 53 and a higher order b excluding the most significant bit in the inputted numerical value Exclusive OR circuit 52 for exclusive ORing with a numerical value consisting of bits
And outputs the output (1 bit) of the NOT circuit 51, the output (b bit) of the exclusive OR circuit 52, the lower a bits and the remaining bits (Lab-1) of the converter. Is transmitted from the output terminal 54.

In this embodiment, since the hash function is used, the bit length b of the output numerical value is shorter than the bit length a of the input numerical value. However, the present invention is not limited to this. The conversion of the bit length in the circuit 53 is of course arbitrary.

Although the above description has been made with a view to preventing unauthorized persons from obtaining information, the apparatus of the present invention may also be used by other persons who send information later. To prevent fraud by denying that the information was transmitted, and to prevent unauthorized persons from transmitting false information by pretending to be authorized persons. What can be done is clear from the literature.

[0048]

As described above, according to the encryption device and the decryption device of the present invention, the input information has the same bit length as the common key and the effective bit length is longer than the common key. One-to-one correspondence between all input information and encrypted information
Since so as to correspond to the bit length of the encryption information can be encrypted so as not to be longer than the bit length of the input information, to improve the transmission efficiency and storage efficiency of information, and encryption
There is an effect that the degree of confidentiality can be improved .

[Brief description of the drawings]

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

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

FIG. 3 is a configuration block diagram of an encryption device according to a third embodiment of the present invention.

FIG. 4 is a configuration block diagram of a decoding device according to a fourth embodiment of the present invention.

FIG. 5 is a configuration block diagram of a code converter and an inverse code converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Code converter 12 Comparator 13 Encryption circuit 14 Switch 21 Inverse code converter 22 Comparator 23 Decoding circuit 24 Switch 31 Switch 51 Negation circuit 52 Exclusive OR circuit 53 Hash function unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G09C 1/00-5/00 H04K 1/00-3/00 H04L 9/00-9/38 JICST file ( JOIS)

Claims (8)

(57) [Claims] 1. A predetermined operation is performed on input information.
And the result of the operation is divided by a predetermined value N.
In an encryption device that outputs the remainder and outputs it as a cipher
A code converter that performs predetermined code conversion on the input information and outputs the result; and an output of the code converter.
X is a predetermined number modulo a given number N
An encryption circuit for performing an encryption process by performing an operation ; a comparator for comparing a magnitude relationship between an output value X of the code converter and a predetermined numerical value N ; according to a comparison result of the comparator , If X is equal to or greater than N , select the output X of the code converter; if X is less than N
Encryption apparatus characterized by comprising a; the selects the output of the encryption circuit, and a switching unit which selectively outputs as the encryption information for the information which is respectively the input to. 2. A predetermined operation is performed on an input cipher.
And the result of the operation is divided by a predetermined value N.
Output the remainder to recover the plaintext information corresponding to the input cipher.
In a decoding device for outputting, a predetermined operation is performed on the input information by using a predetermined numerical value N as a modulus.
A decoding circuit for performing a decoding process by performing an arithmetic operation; a comparator for comparing a magnitude relationship between the value Y of the input information and a predetermined numerical value N ; according to a comparison result of the comparator
If Y is equal to or greater than N, the value Y of the input information is selected, and if Y is smaller than N , the output of the decoding circuit is selectively output. A switching device; and a reverse code converter for performing a predetermined reverse code conversion on an output of the switch and outputting the result as decoding information for the input information. . 3. A predetermined operation is performed on input information.
And the result of the operation is divided by a predetermined value N.
In an encryption device that outputs the remainder and outputs it as a cipher
A first switch for selecting and outputting input original information in accordance with a control signal given from the outside, and then selectively outputting information which has undergone a predetermined encryption process; A code converter for performing a predetermined code conversion and outputting the result; and a predetermined operation modulo a predetermined numerical value N for an output X of the code converter.
An encryption circuit that performs an arithmetic operation to perform an encryption process; a comparator that compares a magnitude relationship between an output value X of the code converter and a predetermined numerical value N ; according to a comparison result of the comparator , X is equal to N or greater than N , the output X of the code converter is selected, and if X is less than N,
The case selects the output of the encryption circuit, the encryption selecting outputs respectively as information the fixed encryption process has been performed
Supply information to the first switch again as input information.
A second switch that enables the operation of encrypting to be repeated a predetermined plurality of times . 4. A predetermined operation is performed on an input cipher.
And the result of the operation is divided by a predetermined value N.
Output the remainder to recover the plaintext information corresponding to the input cipher.
The decoding device that outputs the data first selects and outputs the input original information in accordance with a control signal given from the outside, and then selectively outputs the information that has undergone a predetermined decoding process and re- executes the decoding.
And repeat the operation of decrypting as input multiple times
A first switch capable of performing an operation; and a predetermined value modulo a predetermined value N for an output of the first switch.
A decoding circuit for performing the calculated operation and performing a decoding process;
The output value Y of the first switch and a predetermined value N
And a comparator for comparing the magnitude relation between: Y is equal to N or greater than N according to the comparison result of the comparator
Selects the output Y of the first switching unit for, Y is smaller than N
In this case, the second output for selecting and outputting the output of the decoding circuit
A switching unit; performing a predetermined inverse code conversion on the output of the second switching unit, outputting the same as information subjected to the predetermined decoding process , and supplying the information to the first switching unit;
Serial predetermined multiple of that tighten if possible the operation of decoding the inverse code converter and; decoding apparatus characterized by comprising a. 5. The encryption device according to claim 1, wherein the code converter outputs the input numerical value in a form in which the most significant bit is inverted. . 6. The decoding device according to claim 2, wherein the inverse code converter outputs the input numerical value in a form in which the most significant bit is inverted. apparatus. 7. The encryption device according to claim 1, wherein the code converter is configured to invert a most significant bit in the input numerical value; A circuit for converting a numerical value consisting of lower bits into a numerical value consisting of a predetermined bit length; and a plurality of upper bits excluding the most significant bit in the inputted numerical value, comprising a plurality of higher order bits having the same bit length as the predetermined bit length. An exclusive-OR circuit for performing an exclusive-OR operation on a numerical value and the numerical value having the predetermined bit length; and an output of the NOT circuit, an output of the exclusive OR circuit, the plurality of lower-order bits, and the input. The remaining bits in the calculated numerical value as the output of the code converter; 8. The decoding device according to claim 2, wherein the inverse code converter is configured to invert a most significant bit of the input numerical value; A circuit for converting a numerical value consisting of a plurality of lower bits into a numerical value consisting of a predetermined bit length; and a plurality of upper bits excluding the most significant bit in the input numerical value, the plurality of upper bits having the same bit length as the predetermined bit length. An exclusive-OR circuit for performing an exclusive-OR operation on a numerical value having a predetermined bit length and an output having the predetermined bit length. The output of the NOT circuit, the output of the exclusive OR circuit, the plurality of lower-order bits, and the input The remaining bits in the calculated numerical value as the output of the inverse code converter;