The Federal Data Encryption Standard (DES) is a block product cipher which converts 64-bit blocks of plaintext into 64-bit blocks of ciphertext, or vice-versa, under the control of a 56-bit key. There has in the past been considerable controversy over the adequacy of DES key length. Easily implemented modifications to the DES key schedule (KS) would allow the use of keys longer than 56 bits.
Of course, an algorithm with a modified KS might not conform with the published standard and should not strictly be called "DES."
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