JPH0585141U - Telemetry encryption device - Google Patents

Abstract

(57) [Abstract] [Purpose] It prevents the regularity due to the major frame telemetry data from appearing in the ciphertext, which has a period corresponding to the major frame. [Structure] A PN pattern generating circuit and a scrambling circuit for scrambling major frame telemetry data before formatting are provided. [Effect] It is possible to prevent regularity from appearing in the ciphertext at a cycle corresponding to a major frame, and reduce the sample of the periodicity obtained by a third party who intercepts this by trying to analogize the encryption key.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a telemetry encryption device mounted on an artificial satellite.

[0002]

[Prior Art]

 A device called a telemetry encoder is always installed in the artificial satellite. It collects electrical and mechanical housekeeping data showing the temperature, voltage, current, or operating status of each part of the satellite and the various equipment mounted on it, and puts it in a prescribed format. These data are converted and are generally called telemetry data. This telemetry data is always transmitted to the ground, and on the ground, it is possible to know the operating status of each part of the artificial satellite and various equipment installed by receiving and analyzing this telemetry data. Can be done.

This telemetry data usually has a major frame period of about several [S] identified by a major frame synchronization pattern. Furthermore, the major frame is composed of multiple minor frames. Although the minor frame is identified by the minor frame synchronization pattern, it usually has a period of tens to hundreds [mS]. Most housekeeping data is formatted for telemetry data so that it appears once per minor frame.

However, depending on the type of housekeeping data, there are some that are not expected to change so rapidly over time, and some that are not important as data. In this case, the major frame period It is said that it is enough to obtain the data at. If such data is collected and incorporated into the telemetry data only once in the major frame, the minor frame period will be shortened, the utilization efficiency of the major frame and the minor frame will be improved, and the time will be reduced. It is possible to shorten the sampling period of housekeeping data that changes extremely rapidly.

In order to realize this, in general, a slot for data transmitted only once in one major frame is secured at a fixed position in a minor frame, and a plurality of major frames are configured. The above data shall be transmitted over the following minor frames. The data transmitted in slots other than this slot is necessarily repeated once in each minor frame, but the data in this slot is only repeated once in each major frame. The former data is called Minor Frame Telemetry data, and the latter data is called Major Frame Telemetry data.

On the other hand, in digital communication, a signal from an information source is generally converted into a numerical sequence consisting of “1” and “0”, and a carrier signal is modulated by this binary value, and a wireless or wire transmission line is used. And sent to the destination. Here, it is not impossible to intercept by a third party on any transmission line. Therefore, a so-called cryptographic communication system is constructed in which confidential information source data is encrypted at the transmitting side and decrypted at the receiving side at the destination to restore the signal from the original information source.

As the cryptographic communication system, those based on various principles have been proposed and put into practical use, and one commonly used system is a system called a secret key cryptosystem. In this secret key cryptosystem, methods such as a transposition method that replaces the order of information such as characters and a substitution method that replaces information such as characters with other characters are used. These operations such as character transposition and character replacement are uniquely determined by the algorithm itself and the numerical parameter called the encryption key. The secret key encryption method is not disclosed to the public. .. In this case, the information sent from the transmission source that is encrypted and sent to the transmission path cannot be decrypted by a third party who does not know the encryption key, and can only be decrypted by an authorized receiver who knows it. Become.

[0008] In particular, regarding telemetry data, it is expected that interception by a third party is extremely easy due to the nature of satellite communication, and it is often necessary to encrypt the data. Generally, in order to maintain communication synchronization, the synchronization pattern inserted in the data stream is often not encrypted, and even in the case of telemetry data, only the part excluding the synchronization pattern will be encrypted. However, it is usually sufficient to exclude only the major frame sync pulse from encryption.

FIG. 2 is a block diagram of the above-mentioned telemetry device, and in FIG. 3, reference numeral 3 is the first timing for combining the minor frame telemetry data and the major frame telemetry data and converting them into a predetermined format. Circuit 4 is an encoder for encrypting the output of the first timing circuit, 5 is a second timing circuit for adding a synchronization pattern (major frame synchronization pulse) to the output of the encoder 4, and 6 is a minor Frame telemetry data, 7 is major frame telemetry data, and 8 is telemetry data.

Next, the operation will be described. The minor frame telemetry data 6 and the major frame telemetry data 7 are converted to a predetermined format in the first timing circuit 3 and then encrypted by the encryptor 4 In the second timing circuit, the major frame synchronization pattern is added and the final telemetry data of 5 is output.

[0011]

[Problems to be solved by the device]

 In an encrypted communication system, a third party who illegally intercepts a signal on the transmission line tries to estimate the encryption key by some means from the ciphertext (encrypted information) intercepted on the transmission line. A typical example of this is a known plaintext attack in which a known plaintext is deliberately sunk into the plaintext (information before being encrypted), and the corresponding ciphertext is intercepted. A method of collecting various samples based on the regularity of and then analogizing the encryption key by cut and try is often used. Although a synchronization pattern is required to transmit data, the so-called overhead for synchronizing these communications is usually not encrypted, so there is no guarantee that any data intercepted on the transmission path will have some sort of This is because periodicity appears.

Further, due to the nature of the major frame telemetry data, it is expected that the major frame telemetry data will not change so drastically in time and will have substantially the same value over a considerable period of time. However, in the encryption by substitution or transposition, if the plaintext data is the same, the bit patterns appearing in the ciphertext will be very similar. Therefore, in this case, the major frame synchronization pattern (since the minor frame telemetry data of 6 in FIG. 2 includes the minor frame synchronization pattern, the minor frame synchronization pattern is assumed to be encrypted. Appears in the ciphertext without being encrypted, and the major frame telemetry data that spans multiple minor frames has a bit pattern similar to each other. Will appear in the ciphertext at a cycle equivalent to. For a third party who intercepts ciphertext, this can be powerful information that analogizes the encryption key.

The present invention has been made to solve the above problems, and by scrambling the major frame telemetry data in advance using the PN pattern, the major frame telemetry data can be obtained. It is intended to prevent the appearance of ciphertext in the cycle of major frames.

[0014]

[Means for Solving the Problems]

 The encryption device according to the present invention scrambles major frame telemetry data using a PN pattern. This intermediate data is combined with the minor frame telemetry data to create a predetermined major frame format, and a major frame synchronization pattern is added. By these operations, it is possible to prevent major frame telemetry data from being converted into bit patterns similar to each other and appearing in ciphertext at the cycle of major frames.

[0015]

[Operation] The ciphertext output from this cryptographic device has the periodicity shown by the major frame synchronization pattern, but the major frame telemetry data that does not change so rapidly with time is Since it does not appear in bit patterns similar to each other in a cycle corresponding to a major frame, a third party who intercepts this can reduce the number of samples for deciphering obtained from the periodicity of ciphertext.

[0016]

【Example】

 FIG. 1 is a block diagram of a telemetry cipher device showing an embodiment of the present invention. In FIG. 1, 1 is a PN pattern generation circuit, 2 is a scramble circuit, 3 is a first timing circuit, 4 is an encoder, and 5 is an encoder. The second timing circuit, 6 is minor frame telemetry data, 7 is major frame telemetry data, and 8 is telemetry data.

In the above embodiment, the PN pattern for scrambling the major frame telemetry data is generated, and the scrambling is performed. Therefore, even if the major frame telemetry data does not change at all at time, it is converted into a random bit pattern by this scrambling. Therefore, after being combined with the minor frame telemetry data to form the telemetry format, the probability that some regularity will appear in the major frame in the period corresponding to the major frame pulse becomes very small.

[0018]

[Effect of the device]

 As described above, in the embodiment of the present invention, since the major frame telemetry data is scrambled by the PN pattern, even if the major frame telemetry data does not change at all, it is the minor frame telemetry data. After being combined with the telemetry data and encrypted, the probability that the same bit pattern will appear in a cycle corresponding to a major frame becomes extremely small.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional example.

[Explanation of symbols]

 1 PN pattern generation circuit 2 scramble circuit 3 first timing circuit 4 encryption device 5 second timing circuit 6 minor frame telemetry data 7 major frame telemetry data 8 telemetry data

Claims (1)

[Scope of utility model registration request] 1. A PN pattern generation circuit, a scramble circuit that receives the output of the PN pattern generation circuit and scrambles major frame telemetry data, and a minor that receives the output of the scramble circuit and is externally input. A first timing circuit for converting into a predetermined format in combination with frame telemetry data, an encryptor for receiving the output of the first timing circuit for encryption, and a measure for receiving the output of the encryptor A telemetry encryption device characterized by comprising a second timing circuit for outputting telemetry data to the outside by adding a frame synchronization pattern.