JPS62140531A - Multiplexing device with enciphering function - Google Patents

Abstract

PURPOSE:To make deciphering a key difficult and to improve the secret strength by providing an enciphering function part for receiving a multiplexing signal on a high speed highway and enciphering only a signal of a time slot position to which plural low speed lines are allocated in accordance with the information of a line allocating function part. CONSTITUTION:A low speed line passes through low speed line use channel boards 201-203 and multiplexed by a multiplexing part 1 in accordance with contents 21 of a line allocating information use memory (line allocating function part) 2 in which line allocating information is stored, and allocated to each time slot (TS) on a high speed highway 11. As for a multiplexed signals 11, only a used TS is enciphered by used/unused time slot (TS) information 22 obtained from the memory 2, by an enciphering function part 3, and it is used as a multiplexing signal 31 to be sent out to a transmission line. By the signal 31, an oblique line part 31a, and a pear rind part 31b show an enciphered signal, and a signal of an unenciphered plain sentence, respectively. In such a way, deciphering by a tapper can be protected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to multiplexing in which a plurality of low-speed lines connected to various terminal hosts are multiplexed and placed on a time slot on at least one network. The present invention relates to a device, and particularly to a multiplexing device with an added encryption function.

[Conventional technology]

Conventional multiplexing devices with encryption functions have encryption functions for each low-speed line channel, or on the high-speed highway side for highway support after multiplexing. That is, the multiplexer has an encryption function outside of its original multiplexing function.

[Problem that the invention seeks to solve]

In the former case, each low-speed line has an encryption function, so if the encryption function is provided in a common part of the multiplexer, unused lines will also be encrypted.

Furthermore, if each channel board has an encryption function, the hardware scale will increase.

In the latter case, since each high-speed highway has an encryption function, naturally the bits in unused time slot positions will also be encrypted.

Generally, unused lines and unused time slots have a fixed pattern (in many cases, all 1's), so according to the two conventional methods mentioned above, fixed patterns are encrypted and transmitted on the transmission path. That will happen. When a fixed pattern is encrypted and sent over a transmission path, it is easy for an eavesdropper to infer the part of the plaintext where the plaintext is a fixed pattern, which is called a known plain text atjac.
The state is close to k.

The key becomes easier to decode and the confidentiality strength decreases.

[Means for solving problems]

The present invention overcomes the above-mentioned drawbacks, namely, substantial Kno.
This is to take measures to prevent the key from being completely easily decrypted by a wn plain text attack.

In other words, the multiplexing device targeted by the present invention is equipped with a line allocation function unit that allocates to time slot positions, and by using this line allocation function unit, it is possible to determine which time slots are used on the high-speed highway. You can tell if it is used or not. Therefore, in one aspect of the present invention, the above-mentioned line allocation function section extracts the used/unused information for each time slot and performs encryption processing only on the signals riding on the used time slots.

That is, according to the present invention, there is a line allocation function section that allocates a plurality of low-speed lines to arbitrary or fixed time slot positions on at least one high-speed highway, and according to information of the line allocation function section.

a multiplexing unit that multiplexes the signals of the plurality of low-speed lines and places the multiplexed signal on the high-speed highway; A multiplexer with an encryption function, characterized in that an encryption function section that encrypts only signals at time slot positions to which the plurality of low-speed lines are allocated by the line allocation function section according to information from the allocation function section is completely blind. A device is obtained.

In this way, even when the signal on the high-speed highway flows to the transmission path, there will be an unused time slot.

Unused lines are not encrypted, effectively protecting Kr from eavesdroppers.
It will be protected against iown plain text attack and the like. The time slot use/unuse information is originally a necessary function for the line allocation function, and there is no need to add it in order to implement the one-line encryption method, so the hardware configuration is simple.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1 showing a multiplexing device according to an embodiment of the present invention, 101 to 103 are low-speed line signals.

201 to 203 represent channel boards for low-speed lines.

The low-speed line is multiplexed via the low-speed line channel boards 201 to 203 in the multiplexer 1 according to the contents 21 of the line allocation information memory (line allocation function unit) 2 in which line allocation information is stored. and allocated to each time slot (TS) on the high-speed highway 11. The multiplexed signal 1'1 is further processed by the encryption function unit 3 into the used and unused time slots (TS) obtained from the memory 2 mentioned above.
) According to the information 22, only the used TS is encrypted and becomes the multiplexed signal 31 to be sent to the transmission path.

FIG. 2 shows signals 11, 22, and 31 in FIG. 1, respectively. In the signal 31 in FIG. 2, the shaded portion 31a represents an encrypted signal, and the matte portion 31b represents an unencrypted plaintext signal.

Although the above description concerns the transmitting section of the multiplexing apparatus according to the present invention, the operation for the receiving section is completely reversed, and it is sufficient to decode the signal flowing through the transmission path for only the used TS.

[Effects of the Invention] As explained above, the present invention utilizes the line allocation function without adding any new functions.

Encrypt only the time slots used, Known
pla'in text at/ack'' fI: has the effect of being able to prevent.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a multiplexing device with a cryptographic function according to an embodiment of the present invention, and FIG. 2 is a time chart of signals of each part shown in FIG. 101-103...Low speed line signal, 201-203.
...Low-speed line channel board, 1...Multiplexing section, 2...
- Memory for line allocation information, 21...Line allocation information, 22...Used and unused time slot information. 11...Plaintext multiplexed signal on high-speed highway, 3...
- Encryption function unit, 31... Encrypted multiplex signal. Figure 1 Figure 2

Claims (1)

[Claims] a line allocation function unit that allocates a plurality of low-speed lines to arbitrary or fixed time slot positions on at least one high-speed highway; and multiplexing the signals of the plurality of low-speed lines according to information of the line allocation function unit; and a multiplexing unit for transmitting signals onto the high-speed highway, the multiplexing unit receives the multiplexed signal on the high-speed highway, and uses the line allocation function unit to multiplex the plurality of signals according to information from the line allocation function unit. 1. A multiplexing device with an encryption function, comprising an encryption function section that encrypts only signals at time slot positions to which a low-speed line is allocated.