PROCESS OF CRYPTOGRAPHIC CONVERSION OF BLOCKS OF DIGITAL DATA Russian patent published in 1999 - IPC

FIELD: electric communication, computer engineering, cryptographic methods and devices to cipher digital data. SUBSTANCE: salient feature of process lies in breaking of data block into N≥2 subblocks and in conversion of subblocks by one conversion operation as minimum by turns. This conversion depends on value of input block. Substitution operation realized with k bits of subblock, where 8≤k≤16 is used as operation depending on value of input block. Substitution operations are set by substitution table which number T≥2. Secrete substitution tables are used as substitution tables. In addition binary vector V is formed and substitution table for implementation of substitution operation is chosen by value of vector V. Vector is formed on present step of conversion depending on its value on preceding step of conversion and on value of one of subblocks. EFFECT: increased cryptographic resistance. 2 cl, 3 dwg