DES, created by the NSA, is a 64 bit block cipher, so the following applies:
module Cryptsystem : Cryptsystem_64.T;;
module Cryptmodes : Cryptmodes_64.T with
type key = Cryptsystem.key;;
Key management functions:
Although only 56 bits count a DES key is written with 64 bits. The extra bits are used for parity checking.
val check_parity : string -> unit
Checks that the parity of the key given as string is ok. The string must have a length of 8 characters.
val set_parity : string -> string
Sets the parity bits in the given key and returns a new string.
- DES has been heavily studied and seems to have a rather good design - DES has only 56 bit keys (this means DES should be considered a weak algorithm today, but the variant 3DES is still secure) - DES has been designed to be implemented in hardware, and software implementations are relatively slow - DES is an ANSI and (indirectly) an ISO standard. - There are very few weak keys.
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