A Block Cipher Based Cryptosystem through Modified Forward Backward Overlapped Modulo Arithmetic Technique (MFBOMAT)
Debajyoti Guha · IOSR Journal of Computer Engineering · 2013
In this paper, a new Cryptosystem based on block cipher has been proposed where the encryption is done through Modified Forward Backward Overlapped Modulo Arithmetic Technique (MFBOMAT).The original message is considered as a stream of bits, which is then divided into a number of blocks, each containing n bits, where n is any one of 2, 4, 8, 16, 32, 64, 128, 256.The first and last blocks are then added where the modulus of addition is 2 n .The result replaces the last block (say N th block), first block remaining unchanged (Forward mode).In the next attempt the second and the N th block (the changed block) are added and the result replaces the second block(Backward mode).Again the second (the changed block) and the (N-1) th block are added and the result replaces the (N-1) th block (Forward mode).The modulo addition has been implemented in a very simple manner where the carry out of the MSB is discarded to get the result.The technique is applied in a cascaded manner by varying the block size from 2 to 256.The whole technique has been implemented by using a modulo subtraction technique for decryption.