Product block cipher system for data security

Details Product block cipher system for data security Product block cipher system for data security

1975-02-24

1976-06-08

Birmiel, Howard A.

Telegraphy

Systems

Printing

3401725, H04K 100, H04L 902

Patent

active

039625397

ABSTRACT:
A device for ciphering a block of data bits under control of a cipher key. The cipher device performs a ciphering process for the block of data by carrying out an operation in which the block of data bits is first expanded by duplicating predetermined ones of the data bits. The data bits of the expanded block are combined by modulo-2 addition with an equal number of cipher key bits, selected in accordance with an arbitrary but fixed permutation, to produce a plurality of multi-bit segments forming the arguments for a plurality of different nonlinear substitution function boxes. The substitution boxes perform a plurality of nonlinear transformation functions to produce a substitution set of bits which are equal in number to the number of data bits in the first half of the message block. The substitution set of bits is then subjected to a linear transformation in accordance with an arbitrary but fixed permutation. The combined nonlinear transformation and linear transformation results in a product block cipher of the block of data.

REFERENCES:
patent: 3798359 (1974-03-01), Feistel
patent: 3798360 (1974-03-01), Feistel
"Communication Theory of Secrecy Systems," Shannon, Bell System Technical Journal, vol. 28, pp. 656-715, 1949.
"Cryptography and Computer Privacy," Feistel, Scientific American, vol. 228, No. 5, pp. 15-23, 1973.

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