http://swarm.cs.pub.ro/~mbarbulescu/cripto/Understanding%20Cryptography%20by%20Christof%20Paar%20.pdf http://swarm.cs.pub.ro/~mbarbulescu/cripto/Understanding%2

http://swarm.cs.pub.ro/~mbarbulescu/cripto/Understanding%20Cryptography%20by%20Christof%20Paar%20.pdf http://swarm.cs.pub.ro/~mbarbulescu/cripto/Understanding%20C... The original cipher proposed by IBM had a key length of 128 bits and it is suspicious that it was reduced to 56 bits. The official statement that a cipher with a shorter key length made it easier to implement the DES algorithm on a single chip in 1974 does not sound too convincing