A novel block cipher technique using binary field arithmetic based substitution (BCTBFABS)

In this paper the concept of binary field arithmetic is used to generate block cipher. The technique consists of five stages, where in each of first four stages binary field arithmetic based substitution technique along with key association process is used. The lengths of input and output blocks in these four stages are identical and they are 256 bit, 128 bit, 64 bit and 64 bit, respectively. The last stage consists of a nonlinear S-box operation which may generate cipher block of length different from its input. In most of the cases the proposed algorithm generates space efficient cipher. At the time of decryption, a set of session keys are used in conjunction with the user input key.