Data Encryption Standard

by Mohan 2012-09-21 09:25:02

Data Encryption Standard



The Feistel function (F function) of DES
General
Designers IBM
First published 1977 (standardized in January 1979)
Derived from Lucifer
Successors Triple DES, G-DES, DES-X, LOKI89, ICE
Cipher detail
Key sizes 56 bits
Block sizes 64 bits
Structure Balanced Feistel network
Rounds 16
Best public cryptanalysis
DES is now considered insecure because a brute force attack is possible (see EFF DES cracker). As of 2008, the best analytical attack is linear cryptanalysis, which requires 243 known plaintexts and has a time complexity of 239â43 (Junod, 2001).

The Data Encryption Standard (DES, play /ËdiËËiËËÉs/ or /ËdÉz/) is a previously predominant algorithm for the encryption of electronic data. It was highly influential in the advancement of modern cryptography in the academic world. Developed in the early 1970s at IBM and based on an earlier design by Horst Feistel, the algorithm was submitted to the National Bureau of Standards (NBS) following the agency's invitation to propose a candidate for the protection of sensitive, unclassified electronic government data. In 1976, after consultation with the National Security Agency (NSA), the NBS eventually selected a slightly modified version, which was published as an official Federal Information Processing Standard (FIPS) for the United States in 1977. The publication of an NSA-approved encryption standard simultaneously resulted in its quick international adoption and widespread academic scrutiny. Controversies arose out of classified design elements, a relatively short key length of the symmetric-key block cipher design, and the involvement of the NSA, nourishing suspicions about a backdoor. The intense academic scrutiny the algorithm received over time led to the modern understanding of block ciphers and their cryptanalysis.

DES is now considered to be insecure for many applications. This is chiefly due to the 56-bit key size being too small; in January, 1999, distributed.net and the Electronic Frontier Foundation collaborated to publicly break a DES key in 22 hours and 15 minutes (see chronology). There are also some analytical results which demonstrate theoretical weaknesses in the cipher, although they are infeasible to mount in practice. The algorithm is believed to be practically secure in the form of Triple DES, although there are theoretical attacks. In recent years, the cipher has been superseded by the Advanced Encryption Standard (AES). Furthermore, DES has been withdrawn as a standard by the National Institute of Standards and Technology (formerly the National Bureau of Standards).

Some documentation makes a distinction between DES as a standard and DES as an algorithm, referring to the algorithm as the DEA (Data Encryption Algorithm).
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