Bit Level Multi Way Feedback Encryption Standard Ver-1(BLMWFES-1)

Abstract

Nath et al had developed multi-level feedback encryption standard ver-1, 2 and 3 where the authors have used feedbacks from forward and backward direction. In all the MWFES versions, the authors used byte level encryption and it was found that the results were quite satisfactory. In the present method (BLMWFES-1), the encryption-decryption process was done in bit-level. The entire plaintext was broken up into blocks. For every block, the first plaintext bit, the first key bit, the initial forward feedback bit (FF) and the backward feedback bit (BF) are added and then taken modulo with 2. The bit obtained is the cipher text bit. This cipher text bit was then propagated right to the n1-th bit's forward feedback value. 'n1' is equal to the forward skip (FS) value specific to that block. Next, the last plain text bit of that particular block was added (modulo 2)with the key bit, FF, initial BF and then the cipher text bit obtained was then propagated left, to the n2-th bit's backward feedback value. 'n2' is equal to the backward skip (BS) value of that block. This process of adding the bits (modulo 2) and then propagating it to the appropriate position was done alternately from the left to right and from right to left on the entire block of bits. This completes one round of processing on a single block. After every round of processing, the four important variables such as FF,BF,FS and BS changes dynamically due to changing block size and this makes the encryption very strong. The total number of rounds (encryption number), the block size for every round, initial FF, initial BF, initial FS and initial BS were taken as a function of the keypad. The keypad was generated from the user entered key (seed) using the key-expansion algorithm explained in section-II. This method was then tested on standard plain texts such as ASCII '0', ASCII '1', ASCII '2', ASCII '3' and the results obtained were quite satisfactory. This method is immune to any classical form of attacks.