Browse Prior Art Database

Multichannel Time Share Security System

IP.com Disclosure Number: IPCOM000091067D
Original Publication Date: 1969-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Hsiao, MY: AUTHOR [+2]

Abstract

In a time-share or multiterminal environment, provision has to be made to provide security of information. Each user can select a programmable code as a key for locking and unlocking his data only. The implementation which provides this security consists of a system including an encoder, decoder and mask register. The system uses linear feedback shift registers LFSR's to provide high speed and economy. The programmable code or key is characterized by a generator polynomial of the type g(x) = g(0) + g(1) + g(2) x/2/ + --- + g(r)x/r/. The encoding portion of the circuit in drawing A can be represented by S(t) = S(t-1) T + U(t) where S(t) = the state vector, U(t) = the input vector at time t, and t is the companion matrix which specifies the connections of the LFSR.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Multichannel Time Share Security System

In a time-share or multiterminal environment, provision has to be made to provide security of information. Each user can select a programmable code as a key for locking and unlocking his data only. The implementation which provides this security consists of a system including an encoder, decoder and mask register. The system uses linear feedback shift registers LFSR's to provide high speed and economy. The programmable code or key is characterized by a generator polynomial of the type g(x) = g(0) + g(1) + g(2) x/2/ + --- + g(r)x/r/. The encoding portion of the circuit in drawing A can be represented by S(t) = S(t-1) T + U(t) where S(t) = the state vector, U(t) = the input vector at time t, and t is the companion matrix which specifies the connections of the LFSR. If the mask output at time t is Z(t) and Z(t) = S(t), then in the decoding process, U(t) = Z(t-1) T + Z(t). The decoding equation is the reverse of the encoding equation which is exactly the desired property for decoding. Once the user selects this g(x) polynomial, the encoding portion of the drawing can be activated by the appropriate switches corresponding to the selected g(x) polynomial. The initial state is all 0's and Z(1), Z(2) and Z(3), etc. can be calculated. The decoding can be done by the user unlocking the device by his code. This is done by activating the appropriate switches which are used for encoding and solving for the decoding equation.

The implementation shown in drawing A allows 8-bit parallel encoding and decoding of all messages leaving and entering the information channel. The encoder and decoder are programmable via the mask registers. The mask registers configure the encoder and the decoder to the configuration required for any generator polynomial of degree 8. If generator polynomials of degrees greater or smaller than 8 are required, this is accomplished by adding or removing the identical encoding or decoding stages between bits 0 and 7 as shown in the drawing. The encoding portion of the multichannel security system consists of Exclusive-Or's +, shift registers X and crosspoint switches g. The latter can be replaced by two-way And's. The crosspoint switch allows the encoder to configure to the desired generator polynomial via the mask registers. Registers X store the pre...