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DES TEXT BOOK CONTENT

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The most widely used encryption scheme is based on the Data Encryption Standard (DES) adopted in 1977 by the National Bureau of Standards, now the National Institute of Standards and Technology (NIST), as Federal Information Processing Standard 46 (FIPS PUB 46). The algorithm itself is referred to as the Data Encryption Algorithm (DEA).7 For DES,data are encrypted in 64-bit blocks using a 56-bit key.The algorithm transforms 64-bit input in a series of steps into a 64-bit output.The same steps,with the same key,are used to reverse the encryption. The DES enjoys widespread use.It has also been the subject of much controversy concerning how secure the DES is.To appreciate the nature of the controversy,let us quickly review the history of the DES. In the late 1960s,IBM set up a research project in computer cryptography led by Horst Feistel.The project concluded in 1971 with the development of an algorithm with the designation LUCIFER [FEIS73], which was sold to Lloyd’s of London for us...
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DATA ENCRYPTION STANDARDS

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DATA ENCRYPTION STANDARDS The Data Encryption Standard (DES) is a symmetric-key block cipher published by the National Institute of Standards and Technology (NIST). DES is an implementation of a Feistel Cipher. It uses 16 round Feistel structure. The block size is 64-bit. Though, key length is 64-bit, DES has an effective key length of 56 bits, since 8 of the 64 bits of the key are not used by the encryption algorithm (function as check bits only). General Structure of DES is depicted in the following illustration − Since DES is based on the Feistel Cipher, all that is required to specify DES is − Round function Key schedule Any additional processing − Initial and final permutation Initial and Final Permutation The initial and final permutations are straight Permutation boxes (P-boxes) that are inverses of each other. They have no cryptography significance in DES. The initial and final permutations are shown as follows − Round Function The heart of this ciphe...
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