256 Bits Symmetric-key BLOCK CIPHER ALGORITHM

Abstract

The design and implementation operations of a cipher algorithm are considered an important in any cryptography work because it will be executed as a last stage to the study and analysis of the cipher characteristics like: weakness points and how we will remove it , strong points and how we will increase its power , and how to homogenize the algorithm parts(outputs of parts),so, the paper suggests that a cipher algorithm combines strong features in the block cipher and stream cipher together . In the present version ,the algorithm is composed of two Erasable Programmable Read Only Memories (EPROMs) which has 64 bits storage size ,eight Linear Feed back Shift Registers(LFSRs) which has lengths are: 37 stages ;33 stages 31 stages;29 stages;23 stages;19 stages;33 stages; and 37 stages ,16 bits shifted memory, and set of logic gates. Algorithm inputs are : blocks of plain text each block has 256 bits size , basic encryption/decryption key (has length 20 alphabetic characters) , secondary encryption/decryption key (has length 8 alphabetic characters) , and the specific initial state of EPROMs . The base process In the online(stream cipher) and offline(block cipher) applications is adding the bits of input blocks with the bits of final result of the algorithm components to produce the cipher blocks in same synchronous bits. The additional process that serve the offline applications ,as soon as a block cipher, is reordering locations of bits depend on a scheme ,for all cipher text blocks.