Block substitution based encryption by a modulo 2 addition method and apparatus
First Claim
1. A method of encryption by substituting for any one of the 2n unique clear text blocks of n bit binary numbers an associated unique encrypted block of n bit binary numbers comprising the steps of;
- (a) finding a first set of 2n equations, each equation representing the modulo 2 addition of one of the 2n clear text blocks with a unique one of 2n n bit numbers to provide the associated unique encrypted n bit block, equations in the first set of 2n equations being characterized by the sum modulo 2 of any odd number of the equations being another one of the equations in the first set, where the blocks in each position of a given equation are added modulo 2 to the corresponding blocks in the other equations, whereby any clear text block can be converted into an associated encrypted block by the one to one mapping defined by the 2n equations;
(b) for each clear text block to be encrypted, adding modulo 2 to that block, the unique one of the 2n bit numbers associated therewith in accordance with the associated equation of the first set of 2n equations to obtain the encrypted block.
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Abstract
Methods and apparatus for modulo 2 addition based encryption by block substitution techniques which allows use of the substitution scheme with relatively simple hardware. The block substitution, a one to one mapping of n bit binary numbers onto themselves, is based on the fact that certain permutations of the n bit binary numbers define a block substitution by modulo 2 addition of one permuted set of numbers to another, and that a subset of these define equations having an additive relationship when viewed as vectors. This allows the simple changing of the transformation on a frequent basis. Various properties of the transformations and methods of using the same are disclosed.
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Citations
12 Claims
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1. A method of encryption by substituting for any one of the 2n unique clear text blocks of n bit binary numbers an associated unique encrypted block of n bit binary numbers comprising the steps of;
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(a) finding a first set of 2n equations, each equation representing the modulo 2 addition of one of the 2n clear text blocks with a unique one of 2n n bit numbers to provide the associated unique encrypted n bit block, equations in the first set of 2n equations being characterized by the sum modulo 2 of any odd number of the equations being another one of the equations in the first set, where the blocks in each position of a given equation are added modulo 2 to the corresponding blocks in the other equations, whereby any clear text block can be converted into an associated encrypted block by the one to one mapping defined by the 2n equations; (b) for each clear text block to be encrypted, adding modulo 2 to that block, the unique one of the 2n bit numbers associated therewith in accordance with the associated equation of the first set of 2n equations to obtain the encrypted block. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification