JPS63160444A - Cryptographic communication equipment - Google Patents

Abstract

PURPOSE:To reduce the time required for message communication by encrypting the ciphering and deciphering keys, distributing them to the request reception side and using a ciphering and deciphering keys so as to send a ciphered message thereby eliminating complication of the distribution of the ciphering and deciphering keys. CONSTITUTION:The ciphering and deciphering keys ciphering and deciphering a message to be sent originally are ciphered duplicatedly by the 2nd ciphering device 12 and reciprocated by 1.5 time between both transmission and reception device 51, 52 and distributed to the receiver side device 52. Then the original message ciphered by means of the ciphering and deciphering keys is sent from the sender device 51 and the ciphered message received by the receiver side device 52 is decoded by the ciphering and deciphering keys distributed already. Thus, the ciphering and deciphering keys are distributed safely and the transmission of the original messages is safe and the ciphering and deciphering keys are distributed once, plural message are communication by one way ciphering transmission only, then the time for the transmission is reduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a cryptographic communication device.

[Prior art]

Figure 2 is from rMIT, Laboratory for Computer Science Report 1-TM-125, (Feb.

1979) is a schematic diagram showing the configuration of a cryptographic communication device announced as "Mental Poker" in J.

In the figure, 51 indicates a message sending device, 52 a receiving device, and 53 a communication path between the two.

In this cryptographic communication device, the sending device 51 first sends the message M to be communicated to the first decryption electronic key y using the first decryption key y that satisfies the relationship X-'/=l (mod P-1). A ciphertext C8 encrypted using the encryption i1x is created and transmitted to the receiving device 52 via the communication path 53.

Therefore, the ciphertext C1 is C, :M to (mod P) become.

The receiving device 52 double-encrypts the received ciphertext C3 with the second decryption key a using the second encryption key a that satisfies the relationship a − b = 1 (IIlod P−1). ciphertext C2
is created and transmitted to the sending device 51 via the communication path 53.

Therefore, the ciphertext C2 is c,=c,” E (MX)” ＝M” become.

The sending device 5I that has received the ciphertext C2 uses the first decryption key y for the first encryption key X to generate the double ciphertext C2.
decrypt. That is, C,5Cz' = (M") γ = M" (sod P) (',' x-y=
1) is received by the receiving device 52.

The receiving device 52 that has received the ciphertext C1 decrypts the ciphertext C1 into a message M using the second decryption electronic key for the second encryption key a. That is, (C3)'mi(M
”)' □ = M(sod P) (°, °x−V =
1), the original message M is retrieved.

[Problem that the invention seeks to solve]

Such conventional cryptographic communication devices are excellent in that they can safely deliver encryption and decryption keys without the need for complicated delivery operations, but they do In order to transmit from the sending side to the receiving side, it is necessary to make 1.5 round trips through the communication path, which has the disadvantage that the communication time is too long compared to when communicating ordinary plaintext messages.

The present invention has been made in view of these difficulties, and enables the delivery of encryption/decryption keys without complicated operations, and also avoids the lengthening of time required for message communication. The purpose is to provide a cryptographic communication device that can obtain

C. Means for Solving Problem] In short, the encrypted communication device of the present invention has the same configuration as the conventional encrypted communication device described above, and has an encryption/decryption electronic key for encrypting and decoding messages. First, it is encrypted and delivered to the receiving side, and then the sending side sends a message encrypted with this encryption/decryption electronic key, and the received ciphertext is sent to the receiving side first. It is decrypted using the decryption key.

Specifically, the encrypted communication device of the present invention provides a first method for encrypting an encrypting/decoding electronic key on the sending side in order to deliver an encrypting/decoding electronic key for encrypting and decoding a message.
an encryption device, a second encryption device that double-encrypts the encrypted/decrypted electronic key encrypted by the first encryption device on the receiving side, and the second encryption device 12. A first decryption device that decrypts a heavily encrypted encryption/decryption telephone key on the sending side, and an encryption/decryption telephone key that has decrypted the double ciphertext with this first decryption device. a second decryption device that decrypts the message into an encryption/decryption electronic key on the receiving side; a third encryption device that encrypts the message to be sent with the encryption/decryption electronic key and transmits it to the sending side; and a third decryption device that decrypts the ciphertext of the message encrypted by the third encryption device into a message on the receiving side.

[Effect]

In the cryptographic communication device of the present invention, the encryption/decryption key for encrypting/decrypting the message that should originally be sent is first double-encrypted and sent back and forth for 1.5 times between the sending and receiving devices. This encryption and
The original message encrypted with the decryption key is sent, and the received ciphertext is decrypted on the receiving side using the previously delivered encryption/decryption key.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram showing the configuration of a cryptographic communication device according to the present invention.

In the figure, the range indicated by 51 is the transmitting side device which transmits the message M, and the range indicated by 52 is the receiving ε side device which receives the message M. Note that the two are connected through a communication path 53 such as a telephone line.

The sending device 51 has an input terminal l to the encryption/decryption i1.
and the first encryption 1 for delivery to the encryption/decryption key.
a first encryption device 11 with an input terminal 31 of 1x; a first decryption device 21 with an input terminal 41 of a first decryption key y for delivery to an encryption/decryption key; and an input terminal 3 into which the encryption/decryption key K input from the message M input terminal 2 and the encryption/decryption key input terminal 1 is input.
3 and the like.

The receiving device 52 also includes a second encryption device 12 equipped with an input terminal 32 for a second encryption key a for delivery to the encryption/decryption key; second for
A second decryption device 22 is provided with an input terminal 42 for decryption tub, and an input terminal 43 to which the encryption/decryption key K output from the second decryption device 22 is input. The third decoding device 23 includes a message M output terminal 3, and the like.

The communication path 53 also transmits the ciphertext C output from the first encryption device 11 to the second encryption device 12, and transmits the double ciphertext C2 output from the second encryption device 12. is transmitted to the first decoding device 21, and this first decoding device 2
The ciphertext C3 output from the message M is sent to the second decryption device 22, and the ciphertext C4 of the message M output from the third encryption device 13 is sent to the third decryption device 23.

The operation of the cryptographic communication device of the present invention configured as described above will be explained below.

The first encryption device 11 has an encryption/decryption key input terminal 1
The encryption/decryption key K input from the input terminal 31 is encrypted using the first encryption key X input from the first encryption key input terminal 31. The first encryption device 11 encrypts the encryption/decryption key into a ciphertext C5 and sends it to the second encryption device 12 of the receiving device 52. The encryption key is encrypted into a ciphertext C, with C+ = K X (sod P).

Note that the first encryption key X is the first decryption key y and x −y
There is a relationship of -1 (+IIod P-1).

The second encryption device 12 has a second encryption key input terminal 32.
The ciphertext C1 transmitted from the first encryption device 11 is double-encrypted using the second encryption key a given from the first encryption device 11. At this time, the encryption of the ciphertext C2 is performed as ct=c, "=K" (mad P). Note that the second encryption key a is the second decryption key vI! There is a relationship between b and a-b = 1 (mod P-1). This ciphertext C2 is transmitted from the second encryption device 12 to the first decryption device 21 of the sending device 51.

The first decryption device 21 has a first decryption key input terminal 41
With the first decryption key y given from C! is decrypted into ciphertext C3. This ciphertext C2 to C
Since a−b=L, the decoding to 1 becomes c3=cz′−i=(K″″)γ “K” (modP). This ciphertext C1 is transmitted to the second decryption device 22 of the receiving device 52.

The second decryption device 22 has a second decryption key input terminal 42.
The ciphertext C3 is encrypted and decrypted using the second decryption 1b given by t! Perform decoding to JIK. Since x-y=1, the decryption of this ciphertext C1 is as follows: Cffb = (K'')' = K (IIIod P).

The second decryption device 22 supplies the decrypted encrypted/decrypted northward K to the input terminal 43 of the third decryption device 230.

This completes the transmission of encryption/decryption north from the sending device 51 to the receiving device 52.

Next, the transmission of the message M that should originally be transmitted will be explained.

The third encryption device 13 has an encryption/decryption key input terminal l.
The encryption/decryption Kitashin K input from the input terminal 33
, and a message M that should originally be transmitted from the receiving device 52 to the receiving device 52 is input from the message input terminal 2 .

Then, the third encryption device 13 encrypts the message M input from the message input terminal 2 into a ciphertext C4 using the encryption/decryption code K input from the input terminal 33, and sends it to the receiving side device 52. to the third decoding device 23. This message M is encrypted as c,=rx(M). Here, fK is an encryption function based on encryption/decryption K, and is set by each cryptographic communication device.

The third decryption device 23 first passes the ciphertext C4 transmitted from the third encryption device 13 to the second decryption device 22.
The message M is decoded by the encryption/decryption code K that is decrypted by the input terminal 43 and input to the input terminal 43. This decoding becomes M=fK-'(C4)2fx-'(fx(M)).

However, here, r fK-'J is a decryption function based on encryption/decryption Hokushin K, and is an inverse function of the encryption function fw. The third decryption device 23 uses the ciphertext C4 as described above.
The message M obtained by decoding is outputted from the message output terminal 3 to an output device (not shown), such as a CRT display or a printer.

After this, you can send multiple messages in succession,
Alternatively, it is also possible to set another encryption/decryption method again, deliver the message, and then send another message.

(Effects) As described above, in the encrypted communication device of the present invention, the sending side and the receiving side are individually equipped with an encryption device and a decryption device for sending encryption/decryption forward, and each sends encryption/decryption forward. After encrypting and decrypting the message and delivering the encrypted/decoded message, the sending side encrypts the message that should be sent using this encryption/decryption process and sends it to the receiving side. Since the message is received and decrypted into the original message, the encrypted/decrypted message can be sent safely, and the original message can also be sent safely. Since it is possible to communicate multiple messages using only one-way encrypted transmission, the time required to send them is shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a cryptographic communication device of the present invention, and FIG. 2 is a schematic diagram showing the configuration of a conventional device. 1... Encryption/decryption key input terminal 2... Message input terminal 3... Message output terminal 11
...First encryption device 12...Second encryption device 13...Third encryption device 21...First decryption device 22...Second decryption device 23 ...Third decryption device 51...Sending side device 52...Receiving side device X...First encryption key y...First decryption northward a...Second cipher Encryption key b...Second decoding northward K...Encryption/decoding northward M...message Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A cryptographic communication device that encrypts a message to be transmitted on a transmitting side, transmits it to a receiving side, and decrypts it on the receiving side, which is provided on the transmitting side and that encrypts and decrypts the message. a first encryption device into which an encryption/decryption key is input, encrypts the encryption/decryption key with a first encryption key, and transmits the encrypted key to a receiving side; a second encryption device that double-encrypts the encryption/decryption key encrypted by the first encryption device with a second encryption key and transmits the double-encrypted key to the sender; and decrypts the encryption/decryption key double-encrypted by the second encryption device using a first decryption key for the first encryption key and sends it to the receiving side. a first decryption device; and a second decryption key provided on the receiving side to decrypt the encryption/decryption key decrypted by the first decryption device using a second decryption key corresponding to a second encryption key. a second decryption device that encrypts the message to be sent using the encryption/decryption key and sends the encrypted message to the receiving end, which is provided on the sending end; and receives the ciphertext of the message encrypted by the third encryption device, and sends it to the encrypted message decrypted by the second decryption device.
A cryptographic communication device comprising: a third decryption device that decrypts a message using a decryption key.