JPH05167575A - Ciphering transmission system - Google Patents

Abstract

PURPOSE:To improve the secrecy of transmission information in a satellite line, regarding a ciphering transmission system performing transmission and receptions by ciphering transmission information between mutual earth stations opposing via the satellite line, in a satellite communication system. CONSTITUTION:In a ciphering transmission system provided with a center station 11 transmitting transmission information to a satellite line by ciphering it based on a prescribed key and a reception station 13 receiving the ciphered transmission information from the satellite line and decoding it, the center station 11 is provided with a ciphering means 15 ciphering the key and transmitting it to the satellite line. The reception station 13 is composed by being provided with a deciphering means 17 receiving the ciphered key from the satellite line and obtaining the key to make the deciphering processing of the transmission information efficient by performing a deciphering processing opposite to the ciphering processing to be performed by the ciphering means 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encrypted transmission system in a satellite communication system in which transmission information is encrypted and transmitted and received between opposing earth stations via a satellite line.

[0002]

2. Description of the Related Art In a satellite communication system for sending and receiving mails between companies and between companies via a satellite line, for example, the contents of mails sent and received between a research laboratory developing new products and related departments are In order to avoid a huge loss by leaking to competitors in the same field, an encrypted transmission method is adopted in which documents and image information included in the mail are encrypted and sent to the satellite line.

As an encrypted transmission method, for example, a method of obtaining confidentiality of transmission information by a simple process of multiplying transmission information to be transmitted with an M-sequence PN code is common. Since the encrypted output of such a method can be easily decrypted by a person who has a basic knowledge of encryption, the confidentiality obtained for the transmission information is extremely low.

Therefore, in the satellite communication system, among various encryption methods, DES (Data Encrypt) proposed by IBM Corp. especially for the public invitation of the US Bureau of Standards (NBS).
(ionStandard) method provides high confidentiality by disclosing the encryption method and keeping the key required for decryption secret, and from such characteristics, encryption / decryption equipment and processing equivalent to that equipment can be performed. It has been used conventionally because it is easy to implement the software to perform.

FIG. 4 is a diagram showing an example of the configuration of a satellite communication system using the encrypted transmission system. In the figure, a center station 41 and a receiving station 42 are arranged opposite to each other via a satellite line. In the center station 41, transmission information is given to one input of a transmitter 44 via an encryptor 43, and its output is transmitted to the satellite. Connected to the line. The output of the sub-network encryption key generator 45 is given to the key input of the encryption device 43 and the other input of the transmitter 44.

At the receiving station 42, the satellite line is connected to the input of the receiver 46, one output of which is connected to one input of the decoder 47. The other output of the receiver 46 is the decoder 4
7 key inputs, the output of which is decrypted transmission information.

In the satellite communication system having such a configuration,
The transmitter 44 of the center station 41 transmits the encryption key output by the sub-network encryption key generator 45 to the satellite line without encryption prior to the transmission of the transmission information. Further, the encryptor 43 uses the sub-network encryption key provided from the sub-network encryption key generator 45 to execute the above-mentioned DES.
The transmission information is encrypted by the method, and the encrypted output is sent to the satellite line via the transmitter 44.

In the receiving station 42, the receiver 46 gives the sub-network encryption key received from the center station 41 via the satellite line to the key input of the decoder 47, and further, the key is input from the center station 41. Decoder 4 for the received transmission information
Give to 7. The decryptor 47 decrypts the transmission information encrypted and received from the center station 41 using the above-mentioned sub-network encryption key.

[0009]

By the way, in such a conventional encrypted transmission method, since the sub-network encryption key is transmitted to the satellite line without being encrypted, the content of the key is known by a third party. Therefore, the transmission information may be easily decoded.

An object of the present invention is to provide an encrypted transmission system which can enhance the confidentiality of transmission information on a satellite line.

[0011]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention provides a cipher including a center station 11 that encrypts transmission information based on a predetermined key and transmits the satellite information to a satellite line, and a receiving station 13 that receives and decrypts the encrypted transmission information from the satellite line. In the encrypted transmission method, the center station 11 is provided with an encryption means 15 for encrypting the key and transmitting it to the satellite line, and the receiving station 13 receives the encrypted key from the satellite line and the encryption means. It is characterized by comprising a decryption means 17 for performing a decryption process opposite to the encryption process performed by 15 to obtain a key for improving the efficiency of the decryption process of the transmission information.

[0012]

In the present invention, at the center station 11, the key used for encrypting the transmission information is encrypted by the encryption means 15 and transmitted to the satellite line, and at the receiving station 13, the decryption means 17 is Then, the key transmitted from the center station 11 via the satellite line is decrypted to obtain the key necessary for efficiently decrypting the transmission information.

That is, since the receiving station 13 decrypts the transmission information based on the key encrypted and transmitted from the center station 11, even if the key is intercepted by a third party on the satellite line, Unless the parties know the algorithm of the decryption process performed by the decryption means 17 and the key necessary for the process,
The transmission information cannot be easily decoded.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, parts having the same functions and configurations as those shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted here. The difference between the present embodiment and the conventional example shown in FIG. 4 is that the center station 21 instead of the center station 41 is based on the set individual key between the sub-network encryption key generator 45 and the other input of the transmitter 44. And a scrambler 24 for encrypting the set individual key using the password to be given to the receiving station 25 as a key and recording the encrypted output on the card 23. In the receiving station 25, which replaces the receiving station 42, the output of the receiver 46 and the decoder 47 are provided.
Descrambler 27 which arranges the decryption device 26 between the key input of the decryption device 26 and the key input of the decryption device 26 and applies the same key as the set individual key to the key input of the decryption device 26 according to the password and the information recorded on the card 23. Is equipped with.

Regarding the correspondence between this embodiment and the block diagram shown in FIG. 1, the center station 21 corresponds to the center station 11, the receiving station 25 corresponds to the receiving station 13, and the encryptor 2
2, card 23 and scrambler 24 are encryption means 1
5, the card 23, the decoder 26 and the descrambler 27 correspond to the decoding means 17.

The operation of this embodiment will be described below with reference to FIG. In the center station 21, the system administrator who manages the receiving station gives a password to the receiving station 25 when the receiving station 25 newly opens. Further, the system administrator applies the DES encryption process using the password as the encryption key to the set individual key via the scrambler 24, and writes the encrypted output to the card 23 and sends it to the receiving station 25. To do.

The transmission information is encrypted by the DES as in the conventional example.
In the OFB (Output Feedback) mode, the encryption device 22 sets the sub network encryption key to the DES using the individual key as a key prior to the transmission of the transmission information.
Encryption processing is performed in the ECB (Electric CodeBook) mode of the system. The transmitter 44 transmits the sub-network encryption key encrypted in this way to the receiving station 25. Note that the sub-network key and transmission information encrypted in this way are transmitted and received via a data channel frame of satellite broadcasting, and as indicated by the hatched lines in FIG. 3, a frame synchronization code arranged at the beginning of the frame, A BCH code based on a primitive polynomial having a block length of 63 bits and a parity bit number of 56 is arranged in the latter half of the frame except the frame control code and the range code.

On the other hand, at the receiving station 25, the card 23 sent from the system administrator is mounted on the descrambler 27, and the descrambler 27 is based on the information written on the card 23 and the above-mentioned password. Center station 2
The process opposite to the scrambler 24 of 1 is performed to generate the set individual key. The decryptor 26 performs a decryption process using the thus obtained set individual key as a key on the sub-network encryption key encrypted and received from the center station 21.
Since the decrypted sub-network encryption key is given to the key input of the decryptor 47, the decryptor 47 can decrypt the transmission information encrypted and transmitted from the center station 21 as in the conventional example.

As described above, according to this embodiment, the sub-network key transmitted to the receiving station via the satellite line is encrypted by using the set individual key, and the receiving station decrypts the set individual key. Since the transmission information is decrypted,
Even if a sub-network key transmitted via a satellite line is intercepted by a third party, the transmission information can be easily transmitted if there is no other encryption key recorded on the card and sent to the receiving station to which the key is transmitted. Can not be decrypted into.

Further, in this embodiment, since the transmission frame of the sub-network encryption key and the transmission information can be formed by holding the basic structure of the data channel frame (music data transmission frame) of the satellite broadcasting, the existing center station and This can be easily realized by adding a sub-network encryption key encryption / decryption means to the device of the receiving station.

Further, the same sub-network key is used in parallel between the center station and all receiving stations, but the contents should be updated, for example, every week in the actual operation system. This ensures confidentiality.

In this embodiment, the DES method is adopted as the encryption method of the transmission information, but the present invention is not limited to such an encryption method, and the transmission efficiency and confidentiality required for the system are not limited. Any encryption method may be used as long as it can be secured.

Further, in the present embodiment, the sub-network encryption key is also encrypted based on the DES method, but the present invention is not limited to such an encryption method, and, for example, a public key method or key pre-distribution. The encryption method of the method may be used.

Furthermore, in the present embodiment, an example of the data communication system using the data channel of the broadcasting satellite is shown, but the present invention is not limited to such a communication system.
The present invention can be applied to any satellite communication system as long as it is a system that transmits and receives encrypted transmission information between opposing earth stations via a satellite line.

Further, in the present embodiment, in order to secure confidentiality at the time of delivery of the set individual key to the receiving station, the output of the encryption processing of the set individual key using the password as a key is recorded on the card and the receiving station. However, the present invention can be applied regardless of the delivery method of such a set individual key.

[0027]

As described above, according to the present invention, the center station encrypts the key used for encrypting the transmission information and transmits it to the satellite line, and the receiving station decrypts the key transmitted in this way. Since it is used to decrypt the transmission information, even if a key is intercepted by a third party on the satellite line, the transmission information must be known unless the algorithm for decrypting the key and the key necessary for that processing are known. Is not easily leaked to a third party.

Therefore, the confidentiality of the transmission information on the satellite line is improved, and the safety of the data communication using the satellite line is improved.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a transmission frame of a satellite line.

FIG. 4 is a diagram illustrating a configuration example of a satellite communication system that employs an encrypted transmission method.

[Explanation of symbols]

 11,21,41 Center station 13,25,42 Receiving station 15 Encryption means 17 Decryption means 22,43 Encoder 23 Card 24 Scrambler 26,47 Decoder 27 De-scrambler 44 Transmitter 45 Sub-network encryption key Generator 46 Receiver

Claims (1)

[Claims] 1. A center station (11) for encrypting transmission information based on a predetermined key and transmitting the encrypted transmission information to a satellite line, and a receiving station (11) for receiving and decoding the encrypted transmission information from the satellite line. 13), the center station (11) is provided with an encryption means (15) for encrypting the key and transmitting it to the satellite line, and the receiving station (13) is provided with , A key for receiving the encrypted key from the satellite line and performing a decryption process opposite to the encryption process performed by the encryption means (15) to make the decryption process of the transmission information efficient. An encrypted transmission system comprising a decryption means (17) for obtaining.