JPH01177229A - Key distributing system - Google Patents

Abstract

PURPOSE:To prevent an increase in memory by providing a program for cipher between a center and each terminal and making ciphering of data executable if a key is given. CONSTITUTION:This system is constituted of a center 101 and plural terminals 102, 103.... The user of each terminal sends a ciphered key EC1(K) obtained by ciphering a key K with the code C1 held by the user to the center 101 together with the identifying information (ID1) of the user and the center 101 produces the code C1 by converting the received information ID1 by performing prefixed specific conversion and decodes the ciphered key EC1 (K) so as to obtain the key K. Then the center 101 sends the ciphered key EC1(K) produced by ciphering the key K by using the code C1 obtained by performing prefixed specifiic conversion on the identifying information ID1 to the terminal and, on the terminal side, when the user decodes the received ciphered key EC1(K) by using the code C1 held by the user in advance and obtains the key K. Therefore, it is not necessary to increase the number of memories to be used at the center 101.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a key distribution system for generating and distributing keys used in encryption.

[Conventional technology]

In the conventional key distribution method in a centralized network, the center has all the key encryption keys for each user, and the data encryption key is encrypted and distributed using this key encryption key. It is widely used. In this case, each user only needs to have his or her own key-encrypting key, and does not need to have the key-encrypting keys of other users.

[Problem that the invention seeks to solve]

In the above method, the center needs to hold all the key encryption keys for each user, so as the number of users increases, the memory increases, and each time a new user joins, the center needs to hold all the key encryption keys for that terminal. There is a problem in that it is necessary to add .

[Means for solving problems]

The key distribution method of the present invention is a key distribution method in which a key used for encryption is distributed between a center and a terminal in a network consisting of a center and a plurality of terminals. Ec+(K) encrypted with code CI and this user's identification information IDI
The center converts the received ID using a predetermined specific conversion to create the code C1, and decrypts the Ec+(K) received by C1 to obtain the key. After obtaining the key K, the center side encrypts the key K with a CI obtained by converting the user's identification information IDI using a predetermined specific conversion.
c+(K) to the terminal, and this terminal receives Ec
+(K) is the code C that the user previously possesses.
2 to obtain the key K.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a configuration diagram of an example of a system to which the present invention is applied. This system includes a center 101 and multiple terminals 102.
, 103. ..., such as a computer network or a personal computer communication system. The center and each terminal are equipped with an encryption program, so that data can be encrypted as long as a key is given. An example of an encryption program is the data encryption standard established by the U.S. Department of Commerce Bureau of Standards.
Data Encryption 5 standard,
(hereinafter referred to as DBS).

Figures 1 and 2 are flowcharts of one embodiment of the present invention. Figure 1(a) shows encryption at the terminal when a key is generated at the terminal and sent to the center, and Figure 1(b) shows the encryption at the terminal. is the same decryption at the center, Figure 2 (a) is the encryption at the center when a key is generated at the center and sent to the terminal, and Figure 2 (b) is the same decryption flow at the terminal. It shows. A common digital pattern is set as the key on the transmitting side (from the terminal to the center) and on the receiving side (from the center to the terminal). Each user is given a + key encryption key by the center or network management authority.

Here, if the identification information of user i is IDI, Kl is given by + = f (ID+). f is a function known only to the center and the management organization, and is given by, for example, kl =DESMK(IDI) using the DBS and secret code MK. DES□ indicates conversion by DES using MK as a key. Note that it does not need to be DES as long as it is a secret function.

In Figure 1(a), when the key generation program of the terminal is started, a randomly selected WK is used as a key and this WK is used as the key encryption key input by the user.
EWK=EKl(WK) is obtained (step ■), and the EWK is sent to the center together with the user's identification information IDI (step ■). At the center, follow the steps in Figure 1 (b) to create a + from the IDI to the key encryption key.
), decrypt EWK to obtain key WK (step ■)
. Here, EK (X) and DK (X) mean encryption and decryption using X as a key, respectively. For example, you can use DES here as well.

In Fig. 2 (a), the center randomly generates the key WK (step ■), generates + = f (IDI) as the key encryption key based on the sender's identification information IDI (step ■), and then Encrypt the key WK and EWK=EK+
(WK> is obtained (step ■), and this EWK is sent to the terminal (step ■).

As shown in Figure 2(b), the terminal uses the encryption key EWK.
When the WK is received, it is decrypted using the key encryption key input by the user to obtain the WK (step [shares]).

In the above embodiments, it has been explained that the encryption and conversion f are processed by software using DES, but they may be processed by hardware. Also, IDI
can also use the address of the terminal itself instead of the user's identification information.

〔Effect of the invention〕

As described above in detail, the present invention has the advantage that the memory of the center is small, there is no need to change the center even when a new user joins, and keys can be easily distributed.

[Brief explanation of the drawing]

1 and 2 are flowcharts of an embodiment of the present invention from a terminal to a center and from a center to a terminal, respectively;
The figure is a configuration diagram showing an example of a system to which the present invention is applied. 101...Center, 102, 103...Terminal.

Claims (1)

[Claims] In a key distribution method in which a key used for encryption is distributed between a center and a terminal in a network consisting of a center and a plurality of terminals, the user side of the terminal encrypts the key K with the code C_1 owned by this user E_C_1
(K) and this user's identification information ID_1 are sent together to the center, the center converts the received ID_1 with a predetermined specific conversion to create the code C_1, and the E_C_1 ( K) to obtain the key K, and the center encrypts the key K with C_1, which is obtained by converting the user's identification information ID_1 using a predetermined specific conversion.
C_1(K) to the terminal, and this terminal receives E
A key distribution method characterized in that the key K is obtained by decoding _C_1(K) using a code C_1 that the user previously possesses.