Data Encryption Standard (DES)
The Data Encryption Standard (DES) was published in 1977 by the National Bureau of Standards and was based on the concept later known as Feistel’s Network, developed at IBM.
NBS and IBM agreed on a cooperation involving also the NSA (National Security Agency), who insisted on several modifications of the basic algorithm among which the decrease of the key length from 128 to 56 Bits became the most crucial change.
It is suspected, that the NSA successfully tried to enforce modifications of the DES-scheme to get the possibility to break the algorithm given an unique set of special equipment and computing power at that time. It turned out later that the reduced key length should become the end of the DES, when huge computing power became available to a bigger number of institutions.
DES uses a 56 bit key to encrypt a 64 bit input block of plaintext. The fact that the key is shorter than the incoming message block leads to the introduction of 8 additional parity bits.
For a more detailed description of DES please visit: