A random block length based cryptosystem through multiple cascaded permutation-combinations and chaining of blocks

Abstract

In this paper a four stage character/bit level encoding technique (RBCMCPCC) has been proposed, where the first three steps take input block of length 128 bit, 192bit and 256 bit, respectively, and generate intermediate blocks of the same lengths using identical lengths of keys in each step. The fourth stage generates final cipher blocks based on random session-keys. Before execution of the fourth sage, all 256 bit blocks are passed through the chaining process to ensure the generation of non-identical intermediate stream. A two dimensional matrix based substitution and folding operation is performed in the first stage of encryption, whereas a three dimensional matrix based permutation and substitution operation is done in the next sage. Again, a four dimensional matrix oriented substitution and transposition operation is applied in the third stage. Finally, wrapping operation is done to produce the cipher text. To expound the effectiveness of the algorithm, the obtained results are compared with BAM, TDES, CTSCCT and RSA algorithms.