JPH03198446A - Personal identification number generating system - Google Patents

Abstract

PURPOSE:To prohibit a cryptographic key to be decode even when users are conspired with each other by issuing the personal identification number for the generation the cryptographic key in cryptographic communication to each user in a specific condition. CONSTITUTION:A center 11 is provided with an information file 13, a secret file 14, an inspection register circuit 15, a secret information operating circuit 16, and an ID issuing device 22. The ID issuing device 22 generates (N<2>-N)/2 prime numbers different from each other where N is the number of users for which the personal identification number should be given, and assigns them to all communication lines among users, and the personal identification number of each user is the product of prime numbers assigned to all communication lines connected to the user. Thus, the decoding of secret information in the center 11 is difficult even when two or more users are conspired with each other and safe communication free from leakage of information or the like is available.

Description

[Detailed Description of the Invention] Table of Contents Overview Industrial Field of Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Implementation Examples Summary of Effects of the Invention Sharing of encryption keys for encrypted communication Regarding the generation method of personal identification numbers in the system, in order to make it difficult to decipher the encryption key, it is necessary to ensure that the multiple personal identification numbers used in the encryption key sharing method in encrypted communication are not disjoint, and that any two A method of generating a personal identification number such that personal identification numbers other than the two are not divisible by the greatest common divisor of the personal identification numbers, where N is the number of users to whom a personal identification number should be given,
(N”-N)/2 mutually different prime numbers are generated and assigned to all communication channels between each user, and a user's personal identification number is assigned to all communication channels connected to the user. is the product of prime numbers.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a personal identification number in a cryptographic key sharing method for encrypted communication.

When communicating within a combination network with many users, encrypted communication methods are used to protect the transmitted data. This cryptographic communication method is a conventional cryptographic method (Conventional Cryptos).
system) and public-key cryptography (Public-k
Conventional cryptosystems are also called private key cryptosystems, in which the same key is secretly shared among users, and public key cryptosystems are cryptosystems in which the encryption key is shared publicly. , the decryption key is kept secret, and the decryption key is estimated from the public encryption key. In any of the above systems, the number of users increases as the scale of the network increases, making it difficult to distribute keys and maintain confidentiality. For this reason, the inventors of the present invention proposed a method in which encryption keys are shared between documents at the time of communication without prior communication using personal identification numbers and passwords (encryption key sharing control method: Japanese Patent Application No. 1-118750). .

The present invention mainly relates to a system for generating a personal identification number used in this cryptographic key sharing control system.

Prior Art The principle of the encryption key sharing control method described above will be outlined below. All users participating in the communication must be provided with a personal identification number (I
D) and password (PW) are registered at the center under certain conditions, and the center derives key generation information for each user by the process described below (processing at the center), and then sends this to each user. To distribute. Each user obtains a common key by performing the following processing (processing at the terminal) using his own password and the personal identification number of the communication partner. Note that all variables in the following description are positive integers. Also, * means multiplication.

(1) Processing at the center First, the processing performed in advance at the center will be explained. The center arbitrarily selects large prime numbers p and q (for example, 256 bits), sets n=p"q, and calculates (p-
1) Calculate the least common multiple of (q-1). Also, n
A smaller M and a smaller C than L are arbitrarily selected as the center's secret information.

Individual identification number IDI of each user (n=1.2...
9m1 or less) and the password PWt are set under the condition that they are smaller than the least common multiple, and are coprime to L. The center checks whether the personal identification number IDt from the user satisfies the conditions, and if it does not, requests the user to change it. Then, on the remainder system of L, its reciprocal, that is, ID1
+ -'=1 (madL), ID+-' is determined, and ID-', which is the product of all IDI-', is determined. That is, the password PWt is similarly checked to see if it satisfies the conditions that it is smaller than the least common multiple and coprime to L, and if it is not satisfied, the user is asked to change it. Therefore, on the coset system of L, its reciprocal, that is, P WIX P Wt-'=1 (mo
dL) is obtained and stored together with the corresponding personal identification number IDt.

Next, the center distributes secret information X+ expressed by the following formula to user l.

XX1=C1Dsu・r Dt 'P Wt -'m
od L...■ L = MXX' mod n -・
・■In other words, the center's secret information C and your own personal identification number I
Multiply the reciprocal numbers of all users' IDs except Dt and the reciprocal number of your own password PWI, and take the remainder.
r, and by raising M to the power of this X X t and taking the remainder of n, key generation information X is obtained.

(2) To simplify processing at the terminal, key sharing between user 1 and user 2 will be described. User 1. User 2 sends the personal identification number ID to the center,
, ID2 and password pw.

Pw2 is registered, and the above-mentioned key generation information Xl is registered.

It is assumed that K2 and public information n have been obtained.

User 1 uses the key generation information X+ as his password PW.
After multiplying by +, the common key K12 is obtained by multiplying by the personal identification number IDz of the user 2 who is the communication partner. That is, K12=((XI) Pv') +ll''m
o d n = ((MXX') ”' ) +Il”
mod n= MC umbrella fD *rllll*
PIll Mon PIll*ID2mad n = MC middle IQ middle rDI◆! Mouth 2 mo
d n -... ■User 2 similarly multiplies the key generation information x2 by his own password PW2, and then multiplies it by the personal identification number ID+ of user 1, who is the communication partner, so that 21 is added to the common key. can get. That is, K21=((K2)Pw")"'mo
d n=((M””) ”’) ”’ m
o d nodn = MC in progress! D middle! ! +2 inside"'
mod n 09. ■As above, the formula■
A common key is generated when the expression (2) and (2) match, and the user 1 and the user 2 can create the common key without performing preliminary communication for generating the common key.

This shows how to decipher the case.

User 1 and User 2 have their own personal identification number 10° and ID.
z, αID, α of the formula 10βID2=r
, β, and γ. This can be easily calculated using Euclidean algorithm. At this time, XX = C-ID
-' mod LX = Mxfmod
If n, then from the definition, KIPwl = MXX*ttll K2Pw2 = MXx*fD2 Tealkara, Problem to be Solved by the Invention However, if the personal identification number IDt is carelessly selected in the above method, due to the collusion of two users, It turns out that the center's secret information has been deciphered.

In the following, for example, it is assumed that User 1 and User 2 collude.

When γ=1, user l and user 2 can obtain X and know the keys generated by all users.

In addition, if T≠1, the personal identification number ID is divisible by T.
Suppose there is a user 3 with 3.

If ID*=rIDs', Therefore, the key generated by user 3 can be known.

The present invention has been made in view of these points, and it is an object of the present invention to make it impossible to decrypt an encryption key even if users collude with each other.

Means to Solve the Problem The decryption of secret information (l) occurs when the above γ is 1, that is, when the personal identification numbers of colluding users are disjoint, so the personal identification number set for each user is The numbers must not be relatively prime, and even if T is not 1, if the personal identification number is divisible by T, it is possible to generate a key for the user. It is necessary to set the greatest common divisor so that it is not a divisor of other personal identification numbers.In addition, the personal identification number must be assigned by the center, not registered by the user.

The present invention is a personal identification number generation system that satisfies these conditions, and will be explained below with reference to the principle explanatory diagram shown in FIG. The figure shows a case where the number of users is five.

1 is a center, and U)I (N is 1, 2, . . . , the total number of users) is a plurality of users who communicate. The center 1 has means for generating a prime number, and this prime number generation means
(N2-N)/2 pieces (10 pieces in the figure: 3, 5, 7.
. . ) are generated, and the generated prime numbers are assigned to all communication paths between each user (indicated by the solid line connecting each user in the figure). Then, the product of the prime numbers assigned to all (N-1) communication channels connected to the user to whom the personal identification number is to be given is determined as the personal identification number of the user. For example, for Ul, its personal identification number ID.

becomes 3X5X7X11.

Alternatively, a set of prime numbers assigned to all (N-1) communication channels connected to a user to whom a personal identification number is to be given may be used as the personal identification number of the user. For example, U
, its personal identification number ID, is [3,5,7
, 11), and their product can be taken when generating the shared key.

Furthermore, all prime numbers generated at Center 1 are published as a table with indexes that correspond one-to-one, and correspond to the prime numbers assigned to all communication channels connected to users who should be given personal identification numbers. Let each index of the prime number table be the personal identification number of each user,
At the time of key generation, prime numbers corresponding to each index may be extracted from the public prime number table, and the product of these prime numbers may be calculated.

Effect By applying the present invention, the plurality of personal identification numbers used in the encryption key sharing method in encrypted communication are not disjoint, and the maximum number of personal identification numbers between the respective personal identification numbers of two communicating users is Since it is possible to generate a personal identification number that always satisfies the condition that the personal identification numbers of other users other than the two users are not divisible by a common divisor, even if two or more users collude, it is impossible to decipher the confidential information of the center. This makes it difficult to perform secure communication without information leakage.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing the overall configuration of the first embodiment of the present invention. The center 11 includes an information file 13, a secret file 14, an examination registration circuit 15, a secret information calculation circuit 16,
and an ID issuing device 22 to which the method of the present invention is applied. Further, a plurality of terminals are connected to the center 11. This terminal is used by multiple users, and does not necessarily have one-to-one correspondence with each user, but for convenience of explanation, the terminal used by a certain user k is designated as 12-, and the terminal used by a specific user m is designated as 12-. Assume that the terminal used is 12-m. The terminals 12- and 12-m each have an arithmetic unit 17.
and an encryption device 18.

The ID issuing device 22 performs processing as shown in FIG.
A personal identification number is issued to each user.

That is, when the total number of users constituting the network is N, (N''-N)/2 mutually different prime numbers are generated (step 301), and all communication paths set between each user are (Step 302).Then, the (N-1) prime numbers are assigned to the (N-1) communication paths between the - user and all other users except this one. Calculate the product of prime numbers and use this as the personal identification number of each user (step 303)
.

FIG. 4 is a block diagram showing the configuration of the ID issuing device 22 for implementing the process shown in the flowchart of FIG. 3. The ID issuing device 22 includes a counter 23 and a prime number generation circuit 2.
4, a memory 25, a prime number assignment circuit 26, and a multiplier 27. The prime number generation time v424 is to sequentially generate prime numbers that do not match each other, and when the total number of users is N, prime numbers are generated until the count value of the counter 23 becomes (N'-N)/2, and the prime numbers are sequentially stored in the memory 25. Store in.

The prime number allocation circuit 26 sets communication channels between all users based on the total number of users N, and allocates the prime numbers stored in the memory 25 to each of these communication channels.
Based on the user number i of the user to whom a personal identification number is to be issued, the prime number assigned to the (N-1) communication channels set up between the user and all other users connected to it. It is taken out from the memory 25 and outputted sequentially.

The prime numbers output from the prime number allocation circuit 26 are successively multiplied by a multiplier 27, and when all the corresponding prime numbers have been multiplied, this is used as the personal identification number ID+. A personal identification number ID+ is issued to each user in advance by the ID issuing device 22.

Referring again to FIG. 2, the secret file 14 contains selected large prime numbers p, q (for example, 256 bits).
, the least common multiple of (p-1) and (q-1), a value M smaller than the product n, and a value C smaller than the least common multiple are stored in the information file 13. Personal identification number IDt, password PW, and secret information X+ are stored.

When registering each user's password PW, the test registration circuit 15 checks whether the password PW is smaller than the least common multiple and is coprime to L.
A registration permission signal G/NG is sent to the registration requesting user.

Further, the secret information calculation circuit 16 calculates the parameters n and L stored in the secret file 14 using each user's personal identification number ID, and password PW+.

Based on M and C, secret information XI corresponding to the user is calculated, stored in the information file 13, and sent to the corresponding terminal.

The calculations performed in the secret information calculation circuit 16 are as follows:
Find ID, -' where IDI
'Seek.' That is, ID-'= rI IDt-' mad L Saraso 1 Also, PWI XPWIS=1 (mod L)
Find the FW, -', and find the corresponding personal identification number IDi.
Store with.

Then, xxt = c・ID−′・I Dt −P Wtod
The calculation L L =M"' mod n is performed to obtain the secret information X.

Personal identification number ID of user k who uses terminal 12-k and user m who uses terminal 12-m.

Based on the ID, , and password pw, , pw,
The above calculation is performed, and each user m receives confidential information Xk.
SX- is sent respectively.

Incidentally, the information p, Q, L at the aforementioned center 11.

M and C are secret storage information kept secretly, and prime numbers p and q
The product n is public information. Furthermore, for the user, at least the password PWk PW is kept secretly, and the personal identification number IDkID assigned by the ID issuing device 22 is public information.

Next, processing on each terminal side will be explained. When the user m performs encrypted communication with the user, the calculation unit 17 of the terminal 12- uses the secret information Xk of the center 11.
, own password PWk.

and the personal identification number ID of the user m who is the communication partner.

Based on this, the calculation KEY=((xk)Pwk)+1 mOd n is performed, and the code 1! A KEY is generated.

Similarly, the computing unit 17 of the terminal 12- also operates at the center 11.
Based on the secret information X from , own password FW, and personal identification number IDt of the user who is the communication partner=
d n calculations are performed to generate the encryption key KEY.

This code I! The KEY is manually entered into each encryption device 18, and the encryption device 18 encrypts and sends out the transmitted message based on this encryption key, and also decrypts the received message.

According to the first embodiment, the ID issuing device 22 issues a personal identification number to each user under certain conditions, and under this condition, the personal identification numbers issued to each user are mutually unique. , and the personal identification numbers of users other than the two users are not divisible by the greatest common divisor between the personal identification numbers of any two users, and as a result, two or more users collude with each other. This makes it difficult to decipher secret information, making it possible to conduct secure encrypted communications.

A second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 shows the configuration of the ID issuing device, and FIG. 6 shows the configuration of the terminal. Components similar to those of the above-described first embodiment are given the same numbers and their explanations will be omitted. Fifth
As is clear from a comparison with FIG. 4 (first embodiment), the diagram shows the configuration of FIG. 4 with the multiplier 27 removed.
The personal identification number issued is not the product of each prime number, but a set of prime numbers. That is, a set of prime numbers sequentially output from the prime number assignment circuit 26, for example, [3, 5°7, . . .
] will be issued as a personal identification number ID.

On the terminal side, as shown in FIG.
is provided, and the input ID+' (set of prime numbers) are all multiplied to ID+ and then input to the arithmetic unit 17. This allows the configuration of the center 11 to be simplified.

A third embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 shows the configuration of the ID issuing device, and FIG. 8 shows the configuration of the terminal. Components similar to those of the first embodiment described above are given the same numbers, and some explanations thereof will be omitted.

This ID issuing device includes a counter 30, a prime number generation circuit 31,
It includes a prime number table generation circuit 32 and a prime number assignment circuit 33. The prime number generation circuit 31 sequentially generates prime numbers that do not match each other, and when the total number of users is N, it generates prime numbers until the count value of the counter 30 becomes (N2-N)/2, and generates a prime number table. Output to circuit 32. The prime number table generation circuit 32 attaches indexes (labels) that correspond one-to-one to all manually generated prime numbers to create list-like data, and outputs this as a prime number table 34. This prime number table 34 is public information.

The prime number assignment circuit 33 sets communication channels between all users based on the total number of users N, refers to the prime number table 34, assigns a prime number to each of these communication channels, and issues a personal identification number. User number 1 of the user who should
Based on this, an index corresponding to each prime number assigned to the (N-1) communication channels set between the user and all other users connected to the user is output. Then, the [set of indexes] outputted from the prime number assignment circuit 33, for example, CI, 2, 3°...] (
For example, "1" corresponds to the prime number 3, "2" corresponds to the prime number 5, and "3" corresponds to the prime number 7), and is issued to each user as the personal identification number ID1'.

The configuration of the terminal is shown in FIG.

That is, each terminal includes a prime number extraction circuit 35, a multiplier 36, an arithmetic unit 17, and an encryption device 18. Prime number extraction circuit 35
is based on the manually generated ID+' (index),
Prime numbers corresponding to the indexes are sequentially extracted and output from the prime number table 34, which is public information, and the output prime numbers are sequentially multiplied by the multiplier 36, and the multiplication of the prime numbers corresponding to all indexes is performed. When the process is finished, this is output to the calculation unit 17 as ID+.

In the first embodiment, the personal identification number is a product of prime numbers, but when the number of users increases, the number of digits of the product of prime numbers becomes enormous, making the input by the user complicated and making it inconvenient to handle. However, in the case of the third embodiment above,
Since the personal identification number is used as a set of indexes, such drawbacks can be overcome. Also, center 1
1 can also be simplified.

Effects of the Invention As detailed above, the present invention issues a personal identification number for generating an encryption key in encrypted communication to each user under certain conditions. The personal identification numbers distributed to users are not mutually prime, and the personal identification numbers of users other than the two users are not divisible by the greatest common divisor between the personal identification numbers of any two users; This has the effect that even if two or more users collude, it becomes difficult to decipher the secret information, making it possible to perform secure encrypted communication.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a block diagram showing the overall configuration of the first embodiment of the present invention. FIG. 3 is a flowchart showing the processing of the ID issuing device in the first embodiment of the present invention. 4ryJ is a block diagram showing the configuration of an ID issuing device according to the first embodiment of the present invention, FIG. 5 is a block diagram showing the configuration of the ID issuing device according to the second embodiment of the present invention, and FIG. 6 is a block diagram showing the configuration of the ID issuing device according to the second embodiment of the present invention. 7 is a block diagram showing the configuration of an ID issuing device in the third embodiment of the present invention. FIG. 8 is a block diagram showing the configuration of the terminal in the third embodiment of the present invention. . DESCRIPTION OF SYMBOLS 1... Center, Ul~U,... User, 17... Arithmetic unit, 22... ID issuing device, 24.31... Prime number generation circuit, 26.33... Prime number assignment circuit, 27.28.36... Multiplier, 32... Prime number table generation circuit, 34... Prime number table, 35... Prime number extraction circuit.

Claims (1)

[Scope of Claims] 1. The plurality of personal identification numbers used in the encryption key sharing method in encrypted communication are not mutually prime, and the greatest common divisor of any two personal identification numbers can be used to identify individuals other than those two. This method generates personal identification numbers that are not divisible, and where N is the number of users to whom a personal identification number should be given, (N^2-N)/2 different prime numbers are generated. (24) and assigned to all communication channels between each user (26), and the user's personal identification number is the product of prime numbers assigned to all communication channels connected to the user. Personal identification number generation method. 2. Multiple personal identification numbers used in the encryption key sharing method in encrypted communication are not coprime, and no other personal identification numbers are divisible by the greatest common divisor of any two personal identification numbers. This is a method for generating a personal identification number, in which, when the number of users to whom a personal identification number should be given is N, (N^2-N)/2 mutually different prime numbers are generated (24), and each A personal identification number generation method characterized in that the user's personal identification number is a set of prime numbers assigned to all the communication paths connected to the user (26), and the user's personal identification number is a set of prime numbers allocated to all the communication paths connected to the user. . 3. Multiple personal identification numbers used in the encryption key sharing method in encrypted communication are not mutually prime, and no other personal identification numbers are divisible by the greatest common divisor of any two personal identification numbers. This is a method for generating a personal identification number, in which, when the number of users to whom a personal identification number should be given is N, (N^2-N)/2 mutually different prime numbers are generated (31), and each Assign each prime number to all communication channels between users (33), publish the prime number as an indexed table (34) (32), and assign the user's personal identification number to all communication channels connected to the user. A personal identification number generation system characterized in that a set of indexes of the prime number table (34) is set corresponding to each assigned prime number.