BLOCK CIPHER WITH IMPROVED PARAMETERS OF ARRIVAL TO RANDOM SUBSTITUTION
К.Е. Лисицкий · Legal regulatory and metrological support of information security system in Ukraine · 2017
The main drawback of the known SPN designs of block symmetric ciphers is the extremely small minimum number of S-blocks activated by single-byte differences in the input data blocks. Try to increase the number of S-boxes activated on the first encryption cycles of the Kalina cipher. It is building based on introducing an additional mixing transformation at the input of the cipher by adding modulo 2 data segments at the input of the cipher does not give the expected effect. Indeed, at the input of the cipher, all possible input data block variants should take place. The essence of the proposed new improvement, which is basing on reference to the 256-bit cipher of Kalina after the operation of whitening at its entrance instead of the first cycle of a new cyclic transformation. This transformation includes a layer of consecutively included in the chain of four SL transforms, which are the parallel inclusion of the eight byte S-boxes (ByteSub operation in Kalina), followed by multiplying the values of the S-block outputs by the MDR 8Ч8 matrix (MixColumn operation in Kalina). hile the current SL transform takes an input modulo 2 together with the next input data segment (column) the result of the previous SL transformation. Next, the output value of the last SL transformation in the chain is used to form the last column of the new state matrix, and the outputs of the previous SL transforms after their summation modulo 2 with the output of the last SL conversion are used to form other columns of the state matrix. Finally, the columns of the resulting new state matrix are cycled up to a certain (different) number of bytes (the ShiftColumn operation), stacking them modulo 2 with a cyclic connection (operation XORRoundKey), and outputting a new cycle, the total number of cipher cycles being reduced to eight. For a single-byte difference in the input data block (column) for the rightmost SL conversion of the first layer, in the worst case, one of the S-blocks of this SL transformation is activated, which after the MDS conversion activates all 8-bytes at its output. Subsequent transformation of ShiftColumns performs rearrangement of bytes in each of the columns, which enter the inputs of all SL transforms of the second cycle and activate practically all 32 of its S-blocks, i.e. All S blocks of the second and subsequent cycles are activated. The ciphers are not inferior in speed to known designs and allow us, without reducing the durability, to use in the cipher random S-blocks.