JP3182617B2 - Encrypted communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encrypted communication system effective for improving a data protection function when information is transmitted using a communication line.

[0002]

2. Description of the Related Art FIG. 3 shows a model of a conventional encryption system. A plaintext x, which is information generated from an information source, is encrypted by an encryption function Ek determined by a secret key k, and y = Ek
A cipher text (x) is generated. The encryption function Ek is selected from a set of functions called an encryption function system according to the key. For any key k, the encryption function Ek must be easily computable. In addition, the key k is usually used not fixedly for each plaintext but fixed for many plaintexts.

[0003] The cipher text y is sent to the receiving side through a communication channel. On the receiving side, decoding is performed using a decoding function Dk determined by a key k common to the transmitting side. Dk is the encryption function E
This is the inverse function of k. That is, Dk = 1 / Ek, and plaintext x is restored by D (y) = (1 / Ek) · {Ek (E (x))} = x.

[0004] In the encryption system, the pair of the sender and the receiver has the same key as described above, and furthermore, keeps it secret to protect information from eavesdroppers.

[0005]

However, this communication path is usually not completely protected and can be eavesdropped. An eavesdropper analyzes the ciphertext and attempts to recover the plaintext. In the above method, since there is only one combination of the key and the plaintext, there are the following disadvantages.

If a key is created by a mechanical combination, a correct plaintext can be surely obtained. In other words, if there is enough time, the ciphertext can be decrypted without knowing the key. If the eavesdropper accidentally finds the correct key, the task of finding the key is terminated.Therefore, how much work and time are wasted on the eavesdropper for the strength of the encryption, that is, the decryption. I was dissatisfied with what I said.

[0007] The present invention has been made in view of the above-mentioned points, and eliminates the above-mentioned problems.
Encrypted communication that increases the likelihood of trusting pseudo-information, reduces the reliability of information obtained by eavesdroppers, increases the time spent by eavesdroppers on decryption work, and increases the strength of encryption as a result The aim is to provide a scheme.

[0008]

According to the present invention, there is provided the following means on the transmitting side and the receiving side as shown in FIG.

On the transmitting side, a pseudo key k 'is provided in addition to the conventional normal key k, the normal information x is encrypted by the normal key k, and the pseudo information x' is encrypted by the pseudo key k '. Both are mixed at random and transmitted. On the receiving side, the ciphertext is separated by the regular key k, pseudo k 'and other keys,
There is provided a means for decrypting the part encrypted with the regular key k with the regular key k and decrypting the part encrypted with the pseudo key k 'with the pseudo key k' and outputting plaintext.

[0010]

According to the present invention, regular information x encrypted by the regular key k and pseudo information x 'encrypted by the pseudo key k' are randomly mixed and transmitted to the communication path 9. This makes it very difficult for an eavesdropper to decipher as compared to a single key decipher.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of the encrypted communication of the present invention, and FIG.
The flowchart showing the method of cryptographic translation is shown in FIG.

The encryption transmitting device 1 includes a mixing device 2 for mixing regular information x and pseudo information x '. The legitimate information x is encrypted by a normal key k, and the pseudo information x' is pseudo. Encryption device 3 and transmission device 4 encrypted by key k '
It is composed of

The cipher receiver 5 uses the regular key k for the receiver 6 and the ciphertext y of the pseudo information x ′ for the ciphertext y of the regular information x among the received ciphertexts. Is composed of a decoding device 7 for decoding using a pseudo key k 'and an output device 8. The encryption transmitting device 1 and the encryption receiving device 5 are connected by a communication path 9.

The normal information x input from the transmitting side is randomly mixed with the false pseudo information x 'by the mixing device 2. At this time, a control code is added so that the legitimate information x and the pseudo information x 'can be distinguished. The encrypted regular information x and pseudo information x ′ are mixed by the encryption device 3
The ciphertext is formed using the regular key k and the pseudo key k '. This cipher text is transmitted to the communication path 9 through the transmission device 4.

On the receiving side, the cipher text is received by the receiving device 6, translated by the decrypting device 7, and output as plain text through the output device 8.

The operation of the decoding device 7 will be described below with reference to the flowchart of FIG. A normal key or pseudo
A similar key is entered (usually a regular key is entered) (step STP1). Next, the key is determined (step STP
2) If the key is a regular key, said control code
Then, the part of the cipher text y 'of the pseudo information x' is skipped based on the password (step STP3). Next, the formal cipher text y is decrypted using the formal key k (step STP4), and the formal information x is output through the output device 8 (step STP).
5).

If the key is a pseudo key k ', the control
The ciphertext y part of the regular information x is skipped based on the roll code (step STP6). Next, pseudo information x '
The decrypted by using the 'pseudo key k a portion of' the ciphertext y (step STP7), and outputs the pseudo-information x 'through the output device 8 (step STP 8).

If the key is neither the regular key k nor the pseudo key k ', all the ciphertexts are to be decrypted with the key, so that normal decryption cannot be performed and meaningless processing is performed (step S).
TP9), output meaningless information (step STP1)
0). The above processing is repeated for all data (step STP11).

[0019]

As described above, according to the present invention, the following effects can be expected.

Since two ciphertexts, each encrypted by a different key, are mixed in a communication path, it is expected that it will be very difficult to eavesdrop and decipher the information from the communication path.

Even if two ciphertexts are decrypted, the eavesdropper cannot determine which information is correct. Therefore, the reliability of the information obtained by eavesdropping is reduced.

It is also easy to confuse the enemy by intentionally flowing false information from the receiving end using a pseudo key.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an encryption communication system of the present invention.

FIG. 2 is a diagram showing a processing flow of a translation method of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional encrypted communication system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 encryption transmission device 2 mixing device 3 encryption device 4 transmission device 5 encryption reception device 6 reception device 7 decryption device 8 output device 9 communication path

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09C 1/00-5/00 H04K 1/00-3/00 H04L 9/00 G06F 15/00 330

Claims (1)

(57) [Claims] 1. An encrypted communication system in which information is encrypted on a transmission side and transmitted to a reception side via a communication line, and the encrypted information is decrypted on the reception side . Information is classified into regular and pseudo
Mixing by adding control code to separate
An output of the mixing device and the mixing device.
Regular information on the basis of the provided encryption device for the pseudo encryption information using the pseudo key pseudo information while the regular encrypted information using the authorized key, said on the receiving side The encryption information from the sender is
Based on the troll code, the formal encryption information and the pseudo encryption
Encryption information, and the formal encryption information is
Key to decrypt the legitimate information and
Encrypted information into the pseudo information using the pseudo key
An encrypted communication system comprising a decryption device for decrypting .