JPH0683201B2 - Key delivery device - Google Patents

Description

The present invention relates to key distribution in cryptographic communication.

(Prior Art) IEEE Transactions on Information as a method for delivering keys used for cryptographic communication.
The public key delivery method described in Vol. 22, No. 6, pp. 644 to 654 is well known as a method that enables key delivery by delivering public information and does not require secret transmission means. If it shows concretely, it will be as follows.

The stations that communicate are station 1, station 2, ..., Station N, and now station 1 and station 2
Assume that they are trying to share a key when performing encrypted communication. As public information, a table of code patterns corresponding to each station is open as shown in FIG. Here, the code pattern corresponding to station k is Y _k . Y _k is made from the positive integers α and p determined in advance and the secret positive integer X _k by the following equation.

X _k is a number known only to station k.

At this time, the station 1 creates a key from the public information Y ₂ of the station 2 according to the following equation.

However, A (mod a) indicates the remainder when A is divided by a. Station 2
Creates a key from the public information of station 1 using the following equation.

The formula (2) and the formula (3) have the same numbers as the formula (1).
Here, if p is a large prime number of about 200 digits, and α is a primitive element, a third party will know many Keys even if they know α, p, Y _k (k = 1,2, ..., N). It is shown in the above-mentioned document that the key cannot be known practically because it requires calculation and time.

(Problem of the prior art) If the same encryption key is always used, once it is decrypted, the secret cannot be kept, so it is more secure to change it occasionally. However, the above-mentioned public key distribution technique has a drawback that the keys between the stations 1 and 2 are always the same key unless the public information is changed. Also, if you change the public information from time to time, you have to collect public information from each station,
There is a drawback that it is necessary to confirm whether it is correct information.

(Object of the Invention) The present invention is to provide a key distribution device in which the above drawbacks are eliminated.

(Structure of the Invention) According to the present invention, when performing encrypted communication between at least two stations, that is, the first station and the second station, the plurality of stations are provided for each of the stations performing the encrypted communication. First storage means for storing a first digital pattern determined by the above, second storage means for storing a second digital pattern unique to the local station, random number generation means for generating a random number, and Means for converting the digital pattern of 1 depending on the output of the random number generating means and transmitting it as key distribution data to the partner station, and receiving key distribution data from the partner station and corresponding to the key distribution data and the partner station Means for obtaining a key for encrypted communication with the other station from the first digital pattern, the output of the random number generating means, and the second digital pattern unique to the own station, and the random number generating means in the first station Is the output of The key distribution data obtained as a result of applying the conversion depending on the first random number to the first digital pattern determined for the first station and the first station are determined. Obtained by means for obtaining the key for the encrypted communication from the first digital pattern, the second random number output from the random number generating means in the second station, and the second digital pattern unique to the second station. Digital pattern, key distribution data obtained as a result of applying the conversion depending on the second random number to the first digital pattern determined for the second station, and the second station. Digit obtained by means for obtaining the key for the encrypted communication from the second digital pattern defined corresponding to the second digital pattern, the first random number, and the second digital pattern unique to the first station. Key delivery device is obtained which is characterized by being configured such that Le pattern matches.

(Operation / Principle of the Present Invention) The target communication network is assumed to be composed of N stations. Each station has a secret positive integer corresponding to its own station in addition to the public information shown in FIG. The secret positive integer corresponding to station k is X _k in equation (1). It is now assumed that stations 1 and 2 perform encrypted communication.

FIG. 1 is a diagram showing the operation and principle of the present invention. In the figure, station 1 uses public information Y ₁ , random number R _1, and prime number p Is calculated and sent to the station 2. Similarly for station 2, public information Y ₂ and random numbers
From R ₂ and prime p Is calculated and sent to the station 1. The station 1 uses the public information Y ₂ , the random number R _1, and the secret positive integer X ₁ as Z ₂ sent from the station 2. Is calculated and used as the key. Similarly, station 2 was sent from station 1.
From Z ₁ , public information Y ₁ , the random number R ₂ and secret positive integer X ₂ Is calculated and used as the key. Under the condition of the equation (1), both the results of the equations (5) and (6) be equivalent to. Since the random numbers R ₁ and R ₂ are included, the KEY is different every time.

(Embodiment) FIG. 2 is a block diagram showing an embodiment of the present invention. Before describing FIG. 2, the format of data flowing on the communication network will be described. FIG. 4 is a diagram showing a format example. In the figure, (a) is a general form of data and is composed of a destination address, a source address, control information and data. The control information gives a distinction as to whether or not the data is for key distribution, and if it is for key distribution, it is whether or not the data is for key distribution issued by the station that takes the initiative (the station taking the initiative is the primary station, the other station is the other station). Is called the secondary station). FIG. 7B shows the key delivery data, and Z ₁ is inserted in the data section. However, this is the case where the originating station is station 1. If the originating station is station 2, Z ₂ is included.

In FIG. 2, the RAM 214 holds the public information and secret information shown in FIG. The communication partner station is the station 2, and the own station is the station 1, and the station 1 is the primary station. When the microprocessor 213 receives the key change request from the terminal 211, it generates a random number R ₁ ,
The R ₁ and the public information Y ₁ and Y ₂ of the RAM 214 are passed to the exponentiation remainder circuit 215, and the exponentiation remainder circuit 215 uses Z ₁ shown in the equation (4) as Is calculated and output. The microprocessor 213 passes the Z ₁ to the interface 216, Is stored in the RAM 214. The interface 216 is Z ₁
To station 2. On the other hand, the interface 216 receives Z _{2 represented} by the equation (4) sent from the station 2 and passes it to the microprocessor 213. Microprocessor 213 has RAM ₂ in the Z ₂
14 remembered above Is modulo p and the multiplication result A and the secret positive integer X ₁ are sent to the modular exponentiation circuit 215. The power remainder circuit 215 is Is calculated and output. The microprocessor sets the output in the encryption / decryption unit 212 as a key. After that, the key is used for encrypted communication until the key is changed again.

The exponentiation remainder circuit 215 can be configured by, for example, the circuit shown in "The High-speed Multiplication and Division Method for Cryptographic Processing" 322, National Conference of Information and Systems Division, Institute of Electronics and Communication Engineers, 1981. The interface 216 serves as an interface with the communication network, and is determined if the communication network is specified. For example, if the communication network is Ethernet, the interface consists of a controller and transceiver (Nikkei Electronics 1983 11
See page 139-166 on the 21st of May). A commercially available encryption chip is used as the encryption / decryption device. The operation of the microprocessor 213 is shown in the flow chart of FIG. In (a), station 1 is 1
In the case of the next station, the operation until Z ₁ is transmitted, (b) shows the operation from receiving the key distribution data to setting the key in the encryption / decryption device 212. The actual program is RO
Stored in M217.

In the above description, all the arithmetic operations on integers are used for simplification of the description, but polynomial arithmetic modulo a prime number is also valid. That is, p is a primitive polynomial M
(X), α are primitive elements, and the polynomial can be regarded as a digital pattern by equating it with the coefficient sequence of the polynomial.
Further, although the microprocessor generates the random number, a random number generated outside may be used. Furthermore, after setting the key on the primary station and the secondary station, whether or not the key is the same is determined by the technical reference material “DCNA Function Control Level Protocol Message Transfer Protocol-DCNA” of Nippon Telegraph and Telephone Public Corporation.
PS040-1983- "page 145-146 can be added with the same confirmation function. All of these changes are included in the scope of the present invention.

(Effects of the Invention) As described in detail above, according to the present invention, the random number R ₁ and
R ₂ allows you to set a different key to the encryption / decryption device each time,
The effect is extremely large since encrypted communication with high security can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing the operation and principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing public information, and FIGS. 4 (a) and 4 (b) are communication networks. FIGS. 5A and 5B are flow charts showing the operation of the microprocessor 213, showing an example of the format of the data flowing above. In the figure, 211 is a terminal, 212 is an encryption / decryptor, 213 is a microprocessor, 214 is RAM, 215 is a power-residue circuit, 216
Indicates an interface, and 217 indicates a ROM.

Claims (1)

[Claims] 1. When performing encrypted communication between at least two stations, a first station and a second station, the plurality of stations is a first station defined for each station that performs the encrypted communication. Of the first digital pattern, a second storage means for storing a second digital pattern unique to the local station, a random number generation means for generating a random number, and the first digital pattern A means for performing conversion depending on the output of the random number generating means and transmitting it as key distribution data to the partner station; and a first digital signal corresponding to the key distribution data and the partner station for receiving the key distribution data from the partner station. A means for obtaining a key for encrypted communication with the other station from a pattern, the output of the random number generating means, and the second digital pattern unique to the own station, which is an output of the random number generating means in the first station. Depends on the random number of And key distribution data obtained as a result of applying the conversion to the first digital pattern defined for the first station and the first digital pattern defined for the first station. A digital pattern obtained by means for obtaining a key for the encrypted communication from a second random number output from the random number generating means in the second station and the second digital pattern unique to the second station; Data for key distribution obtained as a result of applying the conversion depending on the second random number to the first digital pattern defined for the second station and the data defined for the second station. A second digital pattern, a digital pattern obtained by means for obtaining the key for the encrypted communication from the first random number, and the second digital pattern unique to the first station. Key delivery apparatus characterized by being configured to.