Nella pagina wikipedia francese sul DES si legge che l'algoritmo DES originale di IBM utilizzava chiavi a 112 bit.
Perché hanno ridotto questo a 56 bit?
Modifica: ok NSA ha convinto IBM, ma oggi sembra un errore. Quindi hanno argomenti oggettivi o semplicemente impongono la loro volontà?
L'NSA ha convinto IBM che 56 bit erano "sufficienti":
But whereas Lucifer had a key that was 112 bits long, the DES key was shortened to 56 bits at the request of the National Security Agency.
da UNIX pratico & Sicurezza Internet
In the development of DES, NSA convinced IBM that a reduced key size was sufficient
da Data Encryption Standard - Wikipedia
The NSA made two changes to DES: It tweaked the algorithm, and it cut the key size by more than half.
La dimensione della chiave è stata ridotta a 56 bit perché IBM desiderava installare LUCIFER su un singolo chip. LUCIFER divenne quindi DES.
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.
Stallings, W. Cryptography and network security, 5th ed .. p.78
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