Lucifer (cipher)

Lucifer is the name given to several of the earliest civilian block ciphers, designed by Horst Feistel and his colleagues at IBM. Rather than a single fixed algorithm it was a family of related designs, and it stands as a direct precursor to the Data Encryption Standard, the block cipher that later became a widely used public standard. One version of the family, also known by the name DTD-1, was put to commercial use during the 1970s for electronic banking, which makes Lucifer one of the first block ciphers to protect real financial traffic outside military and government settings. It matters in the history of cryptography as the point where the Feistel approach to building block ciphers moved from research into deployed products.