METHOD FOR THE CRYPTOGRAPHIC CONVERSION OF L-BIT INPUT BLOCKS OF DIGITAL DATA INTO L-BIT OUTPUT BLOCKS

摘要

The present invention pertains to the field of electronic communications and computer techniques and more precisely relates to cryptographic methods and devices for ciphering digital data. The method of the present invention comprises dividing a block of data into a number N>/=2 of secondary blocks. These secondary blocks are further converted one after the other by generating at least one dual vector according to each secondary block value and by modifying said secondary block using said dual vector. This method is characterised in that, during the next conversion step of a secondary block, the dual vector is generated according to the structure of the dual vector used in the previous conversion step of a secondary block. This method is also characterised in that two dual vectors are generated, wherein one dual vector is converted by a cyclic shifting operation on a number of bits which is equal to the value of the other dual vector. This method is further characterised in that one of the secondary blocks is modified by applying to it a cyclic shifting operation on a number of bits which is equal to the current value of the dual vector. During secondary block conversion, this method uses a number T>/=2 of stuffing tables. The number (v) of the table is calculated on the basis of the dual vector and the secondary block is modified by a stuffing operation determined by the v-th table.