METHOD FOR ITERATIVE ENCRYPTION OF DIGITAL DATA BLOCKS Russian patent published in 2002 - IPC

FIELD: electric communications and computer engineering; data encryption methods. SUBSTANCE: method involves private key generation, data block division into two subblocks, and execution of R≥2 encryption, these operations including conversion of first sub-block by means of sequence of L₁, L₂,..., L_n operations, where n > 1, and conversion of second sub-block by means of sequence of H₁, H₂,...,H_m operations, where m > 1; at least one of L₁, L₂,..., L_n, H₁, H₂,..., H_m operations is controlled operation and control vector is generated prior to this operation; during execution of at least one of L₁, L₂,..., L_n, H₁, H₂,..., H_m operations use is made of one of sub-keys ; m is even number and n is odd number; in addition sub-blocks are re- arranged in all encryption rounds except for last one upon execution of L_n and H_m operation; H_i operations are reverse to H_m-i+1 operations, where 1≤i≤m/2; L_n-j+1, where 1≤j≤(n-1)/2 ones; two-place reversible controlled operation is used as L_(n-1)/2+1 operation and before its execution control vector is generated depending on second block. EFFECT: enhanced resistance to differential cryptanalysis. 4 cl, 2 dwg