JPS6354037A - Key distributing device - Google Patents

Abstract

PURPOSE:To increase the efficiency of a key distribution by using a secret integral number specific to a user so as to convert a random number and forming a key distribution data, thereby generating a ciphering communication key under a prescribed condition. CONSTITUTION:A secret integral number and a public integral number in common to membership are stored in the card 203 of a user A and the numbers are read in a terminal 201 via a card reader 202. A terminal equipment 201 generates a random number at the key distribution processing, the number is converted by using the secret integral number and the public integral number and sends the converted random number to a communication opposite party B as a key delivery data, receives the key delivery data generated by the similar procedure from the opposite party B and discriminates whether or not the data is a data satisfying a prescribed condition according to the predetermined algorithm. When the condition is satisfied, the key distribution data is converted depending on the random number generated by the predetermined conversion and the result of conversion is used as the ciphering communication key.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a key distribution device used for encrypted communication.

(Prior art) Public-key cryptosystems and public-key distribution systems are based on Diffie and Hellman's Transactions on Information Theory (IEEETrans).
actions on information Th
This is the method proposed in Vol. 22, No. 6, pp. 644-654 of ``Eory''. These methods use publicly available information to encrypt messages and convert encryption keys.

(Problem to be solved by the invention) Since the above-mentioned disclosed information differs depending on the communication partner,
The disadvantage is that the total amount is enormous if you include all of Tokyo, and you have to be careful at all times to make sure it is not tampered with.

(Means for Solving the Problems) The key distribution device of the present invention generates random numbers and converts the random numbers into a predetermined secret code and a digital pattern that is common to communication parties and does not necessarily have to be secret. key distribution data creation means for converting the random numbers according to a predetermined conversion and sending the converted random numbers to the communication partner as key delivery data; and means that is the same as the key delivery data creation means at the communication partner. receives the key distribution data created in , determines whether or not the key distribution data satisfies predetermined conditions according to a predetermined algorithm; The key distribution device is characterized in that the key distribution device includes cryptographic communication key generation means that performs conversion depending on the random number generated in the conversion and uses the conversion result as a cryptographic communication key.

(Operation) Prior to a detailed explanation of the present invention, the principles and operations common to each embodiment will be explained using FIG. 1 for ease of understanding. In FIG. 1, it is assumed that an encryption key is shared between user A and user 3, and that user A initiates the activation. User A has a secret integer SA and integers e, c, α, which do not necessarily have to be secret (hereinafter referred to as public).
, n, and user B has a secret integer SB and the public integer e
, c, α, n. These integers are determined and distributed in advance by a reliable person or organization. The method of determining this will be explained later.

User A generates a random number r, XA = a” (mod
n) and yA= SA・a” (mod n),
(XA13'A) is sent to user B. Here a(mod
b) means the remainder when a is divided by b. User B is (
Take XA, yA), yAe/xAC (modn)
It is determined whether or not is equal to A by encoding A's address, name, etc. If they are not equal, the key distribution process is canceled. If they are equal, user B also generates a random number t, and xB =
aet(mad n) and yB = SB・aCt(m
od n), sends (xBlyB) to user A, and sends the data encryption key wk to wk=xAt(mo
dn). wk is equal to aer'(modn). On the other hand, user A receives (XB, yB) and yBe
Determine whether /xBc (mod n) is equal to B, which is the encoded address, name, etc. of user B. If they are not equal, stop the key distribution process, and if they are equal, set the data encryption key Wk to wk=xBr (mod n). This Wk is also equal to αert (mod H). In addition, ID
Although A is known to everyone, user A may notify user B.

Now, assume that SA, SB, e, c, α, and n are defined as follows. Let n=p-q be prime numbers that differ in size to the extent that it is difficult to factorize n. for example,
p.

It is sufficient if both q are about 2256. Let e and c be prime numbers less than n, and α be a positive integer less than n. Furthermore, d is e-
As an integer that satisfies d (mod (p-1) (q-1)) = 1, SA = IDAd (mod n), SB =
IDBd (mod n).

When SA, SB, e, c, α, and n are defined as above, SAe (mod n) = IDA, SBe
(mod n) = IDB. This is a magazine communication, Z op the NCM (Com
21 of the ACM)
This is true because it is the same process as the so-called R8A public key cryptographic encryption and decryption described on pages 120 to 126 of Vol. 2, No. 2.

Then, modulo n, yAe/XAC=SAe, αer
C/αerC=IDA. yBe/xBC= ID
The same applies to B. However, since SA is held only by user A and sB is held only by user B (however, the trusted person or institution that created SA, SB, etc. shall not commit fraud), yAe/XAC(modn) = ■ Only user A can create (XA, yA) that satisfies DA, yBe/xB
Only user B can create (xB, yB) that satisfies C (mod n) = IDB. Here, xf(
mod n) = b is difficult because it corresponds to breaking the R8A public key cryptosystem. Furthermore, it is stated in the above-mentioned IEEE literature that wk cannot be determined from XA, xB, and n. Note that key distribution can also be done by making C variable and notifying the other party.

From the above, it has been shown that each user can perform key distribution by simply having his own secret integer S and e, c, α, and n that are common to all users.

(Embodiment) FIG. 2 is a block diagram showing a first embodiment of the present invention. 2
01 is a terminal, for example a personal computer,
202 is a card league, 203 is a card, and 204 is a line connected to a communication partner. Any card may be used as long as the contents cannot be read by others, but if there is a risk of it being read, an IC card is better. Let the user be A. Card 203 includes SA, e, c, α,
n is stored and read by the terminal 201 through the card reader 202. The terminal 201 includes a card reading program, a random number r generation program, αre and SA・αrc.
There are calculation programs, programs for transmitting and receiving data to the other party, etc. The work to be done by the terminal is shown in flowcharts in FIGS. 3(a) and 3(b). When entering the key distribution process shown in FIG. 3(a), first a random number r is generated, SA, e, c, α, and n are read from the card, and KA and yA are calculated and sent to the other party. Next, in Fig. 3(b), if xB13'B is also sent from the other side, yBe/xBC(m
od n), and if it is equal to IDH, wk = xB
Let r(mod n) be the data encryption key. If they are not equal, the key distribution process is canceled. Further, the key delivery process is also canceled when XB and yB are sent from the other party and there is no rice. If the process is canceled, the process is retried or an alarm is issued to notify the other party's terminal.

Note that part or all of the work on the terminal may be performed using dedicated hardware instead of software. Furthermore, the card reader 202 may be incorporated into the terminal 201.

FIG. 4 is a block diagram showing a second embodiment of the present invention. In FIG. 4, the device of the present invention is realized as a board connected to a terminal device 401. 404 is a random number generator that generates random numbers r and t; 405 is an exponentiation remainder circuit that calculates an exponentiation remainder; 406 is a multiplication/division circuit; 407 is a microprocessor; 402 is a microprocessor; The ROM 403 is the RAM of the microprocessor 407's work area. Public information e, c
, α, and n are stored in the R,OM 402, but the secret information SA is incorporated in the multiplication/division circuit 406, and yA=S
The multiplication/division circuit 406 executes the multiplication/division at "A・α" (tnod n).The microprocessor 407 controls the work shown in FIG. If available, the latter can be used instead.

In the above explanation, d, p, (1 used when creating s, e, c, α, n will become unnecessary once s, e, c, α, n are distributed to each person, You can discard it.Also, y
Ae/XAC (modn) does not need to completely match ■DA as long as it is similar. This is because if someone who does not know SA creates XA+yA, yAe/XAC (modn) will be a random number and will most likely be completely different from ■DA. The ID is not fixed, and any ID that can identify the user A may be used, even if it is not an address or a name. Furthermore, although S, C, e, C, and n have been explained as integers, the exact same argument holds true even if they are elements of a finite field.

All of these modifications are included in the present invention.

(Effects of the Invention) As described above in detail, the present invention has the effect that each user can perform key distribution with only one secret information and several pieces of public information.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the operation of the present invention, FIG. 2 is a block diagram showing the first embodiment of the present invention, and FIGS. 3(a), (
b) is a flowchart showing the work to be done by each terminal, and FIG. 4 is a block diagram showing the second embodiment. In the figure, reference numeral 101 indicates processing by the user on the activation side, 102 indicates processing by the user on the activation side, 201 is a terminal, 202 is a card reader, 203 is a card, and 204 is a cable connecting with the other party terminal. 401 is a terminal device, 402 is RO
M, 403 is a RAM, 404 is a random number generator, 405 is a power remainder circuit, 406 is a multiplication/division circuit, and 407 is a microprocessor.
2d-Death; Station Rib Figure 2

Claims (1)

[Claims] A key distribution device that distributes a key to be shared with a communication partner during encrypted communication generates a random number, and converts the random number into a predetermined secret code and a digital pattern that is common to the communication parties and does not necessarily have to be secret. key distribution data creation means that converts the random number according to a predetermined conversion and sends the converted random number as key distribution data to the communication partner, and the same rules as the key delivery data creation means in the communication partner; receives the key distribution data created in , determines whether or not the key distribution data satisfies predetermined conditions according to a predetermined algorithm; A key distribution device comprising: cryptographic communication key creation means that performs conversion depending on the generated random number and uses the conversion result as a cryptographic communication key.