JPH0618367B2 - Key delivery method - Google Patents

Description

The present invention relates to a key distribution method for generating and distributing a key used for encryption.

[Conventional technology]

In the conventional key distribution method in the centralized network, the center has all the key encryption keys with each user, and the method that encrypts the data encryption key using this key encryption key and distributes it It is used a lot. In this case, each user need only have his or her own key encryption key, and need not have any other user's key encryption key.

[Problems to be solved by the invention]

In the above-mentioned method, the center needs to have all the key encryption keys with each user, so that the memory in which the number of users increases increases and the key encryption key for the terminal is added each time a new user joins. It has a problem that it needs to be added.

[Means for solving problems]

The key delivery system of the present invention is a key delivery system in which a key used for encryption is delivered between a center and a terminal in a network including a center and a plurality of terminals, and the user side of the terminal has the key K for this user. E _ci (K) encrypted with the code Ci and the identification information ID _{i of} this user are sent to the center, and the center converts the received ID _i by a predetermined specific conversion to obtain the code C
_i, and the key K is obtained by decrypting the E _ci (K) received by the C _i , and the center side transforms the identification information ID _{i of the} user by a predetermined specific conversion. E encrypted the key K with C _i
sent _ci (K) to the terminal, which received E
_The code C that the user has in advance _ci (K)
_It is constructed by obtaining the key K by decrypting with _i .

〔Example〕

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

FIG. 3 is a block diagram of an example of a system to which the present invention is applied. This system includes a center 101 and a plurality of terminals 10.
2, 103, ..., For example, a computer network or a personal computer communication system. An encryption program is provided in the center and each terminal, and the encryption of data etc. can be executed if a key is given. The encryption program is, for example, a data encryption standard (Da
ta Encryption Standard, hereinafter referred to as DES).

FIGS. 1 and 2 are flowcharts showing an embodiment of the present invention. In FIG. 1 (a), the encryption at the terminal when the key is generated by the terminal and sent to the center is shown in FIG. 1 (b). Similarly, FIG. 2 (a) shows decryption at the center, FIG. 2 (a) shows encryption at the center when a key is generated and sent to the terminal, and FIG. 2 (b) similarly shows decryption flow at the terminal. Is shown. Keys are sender (from terminal to center) and receiver (from center to terminal)
And set a common digital pattern. Each user is given a key encryption key K _i by the center or the management organization of the network. Here, assuming that the identification information of the user i is ID _i , K _i is given by K _i = f (ID _i ). f is a function known only to the center and the management organization, and is given by, for example, k _i = DES _MK (ID _i ) using the DES and the secret code MK. DES _MK indicates conversion by DES using MK as a key. A secret function may be used instead of DES.

In FIG. 1 (a), when the key generation program of the terminal is started, WK randomly selected is used as a key (step), and WK is encrypted with the key encryption key K _i input by the user to obtain EWK = E _Ki. After obtaining (WK) (step), the EWK is sent to the center together with the user identification information ID _i (step). According to FIG. 1 (b), the center creates a key encryption key K _i from ID _i (step) and decrypts EWK to obtain key WK (step). Where E _K (x) and D _K (x) are each x
Means to encrypt and decrypt with the key K. For example, DES can be used here as well.

In FIG. 2 (a), the center randomly generates a key WK (step), and generates a key encryption key K _i = f (ID _i ) based on the identification information ID _i of the sender (step), With this, the key WK is encrypted and EWK = E _Ki (W
K) is obtained (step), and this EWK is sent to the terminal (step). At the terminal, as shown in FIG.
When the encryption key EWK is received, the key encryption key K _i input by the user is decrypted to obtain WK (step).

In the above embodiments, the DES is used for the encryption and conversion f, and the processing is performed by software. However, the processing may be performed by hardware. Also, ID
_{For i} , not the identification information of the user but the address itself of the terminal can be used.

〔The invention's effect〕

As described in detail above, according to the present invention, the memory of the center is small, there is no need to change even when a new user joins, and the key can be delivered easily.

[Brief description of drawings]

1 and 2 are flow charts of an embodiment of the present invention from the terminal to the center and from the center to the terminal, respectively.
FIG. 1 is a block diagram showing an example of a system to which the present invention is applied. 101 ... Center, 102, 103 ... Terminals.

Claims (1)

[Claims] 1. In a key delivery system for delivering a key used for encryption between a center and a terminal in a network consisting of a center and a plurality of terminals, a user of the terminal has a code C possessed by a key K held by the user. E encrypted with _i
Ci (K) and this user's identification information ID _i are sent together to the center, and the center converts the received ID _i by a predetermined specific conversion to create the code C _i ,
The key K is obtained by decrypting the E _ci (K) received with the C _i , and the center side uses the C _{i obtained} by converting the user identification information ID _i by a predetermined specific conversion. The key K is sent by sending an encrypted E _ci (K) of the key K to the terminal, and the terminal decrypting the received E _ci (K) using the code C _i that the user previously possesses. A key delivery method characterized by obtaining.