Scrambling/descrambling method using a memory for storing initia

Details Scrambling/descrambling method using a memory for storing initia Scrambling/descrambling method using a memory for storing initia

1989-02-27

1991-04-09

Tarcza, Thomas H.

Cryptography

Key management

Having particular key generator

380 49, 375114, 3701051, H04L 900

Patent

active

050070886

ABSTRACT:
In a communications system, a multiframe data signal is sent from a transmit end to a receive end of the system. The multiframe is composed of a series of submultiframes each containing a series of frames. Each frame in turn comprises a sync word for establishing the start timing of the frame, an identifier for uniquely identifying the submultiframe in which the frame is contained, and a specified number of data bits. A pseudo-random scrambling bit pattern, which repeats at intervals of multiframe and varies from one pattern to another at frame intervals, is generated as a scrambling bit pattern with which the data bits of each frame are scrambled prior to transmission. At the receive end, the sync word of each frame is detected to establish frame synchronization. A memory stores initial bit patterns each of which is identical to the pattern which was generated at the beginning of each submultiframe. The identifier is detected when frame sync is established and applied as a read address to the memory. The initial bit pattern of the submultiframe which is next to a one in which the establishment of frame sync occurred is read out of the memory into a pseudo-random sequence generator. The latter is activated at the beginning of the next submultiframe to generate a pseudo-random sequence, which successively varies at frame intervals and repeats the same pattern at multiframe intervals, for descrambling received data bits.

REFERENCES:
patent: 4606042 (1986-08-01), Kahn et al.
patent: 4663501 (1987-05-01), Pospischil
patent: 4757536 (1988-07-01), Szczutkowski et al.
patent: 4817148 (1989-03-01), Lafferty et al.

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