Annotated Bibliography On Data Encryption Standard

1.1 Data Encryption Standard Data Encryption standard was one of the predetermined symmetric algorithms for the encryption of data. DES was developed in early 1970s at IBM and based on an earlier design by Horst Feistel. DES is one of the most and significant modern symmetric encryption algorithm, for many years DES was known as â€Å"secret code making†. The algorithm was developed in early 1970s, but due to some controversies the algorithm was published in January 1977 as an algorithm to be used for the unclassified data. The data encryption standard, as specified is a block cipher operating on the 64 bit data block. DES also uses a key to customize the transformation, so that decryption can be only be performed by those who know the†¦show more content†¦Key mixing: the expansion word is XORed with a round key constructed by selecting 48 bits from the 56 bits secret key, a different selection is used in each round. Substitution: the 48 bits result is split into eight bit words which are substituted in eight parallel 6 * 4 bit S-boxes. All the S-boxes, are different but have the same special structure. Permutation (P): the resulting 32 bits are reordered according to a fixed permutation before being sent as the output. 1.3 ALGORITHM [1] In the first step, the 64 bit plain text block is handed over to initial permutation (IP) function. [2] The initial permutation is performed on the input plain text. [3] The initial permutation results in two halves of permuted block: LBlock and RBlock. [4] Each of LBlock and RBlock goes through 16 rounds of the encryption process, each with its own key. [5] From the 56 bit key, a different 48 bit sub key is generated using the transformation. [6] The 48 bit is XORed with the 48 bit RBlock and the resulting output is given in the next step. [7] Using the S-box substitution procedure the 32-bit from 48-bit input. [8] These 32 bit are permuted using P-box permutation. [9] The P-box output 32 bits are XORed with the LBlock 32 bits. [10] The result of the XORed 32 bits is become the RBlock and the old RBlock becomes the LBlock. This process is called swapping. [11] The RBlock