Cryptography: Avalanche Effect in DES

•A desirable property of any encryption algorithm is that a small change in either the plaintext or the key should produce a significant change in the ciphertext.

•In particular, a change in one bit of the plaintext or one bit of the key should produce a change in many bits of the ciphertext.

•This is referred to as the avalanche effect. If the change were small, this might provide a way to reduce the size of the plaintext or key space to be searched.

Cryptography: History of Data Encryption Standard (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, which was sold to Lloyd’s of London for use in a cash-dispensing system, also developed by IBM.

•LUCIFER is a Feistel block cipher that operates on blocks of 64 bits, using a key size of 128 bits.

•Because of the promising results produced by the LUCIFER project, IBM embarked on an effort to develop a marketable commercial encryption product that ideally could be implemented on a single chip.

•The effort was headed by Walter Tuchman and Carl Meyer, and it involved not only IBM researchers but also outside consultants and technical advice from the National Security Agency (NSA).

•The outcome of this effort was a refined version of LUCIFER that was more resistant to cryptanalysis but that had a reduced key size of 56 bits, in order to fit on a single chip.

•In 1973, the National Bureau of Standards (NBS) issued a request for proposals for a national cipher standard. IBM submitted the results of its Tuchman–Meyer project. This was by far the best algorithm proposed and was adopted in 1977 as the Data Encryption Standard.