EFF DES cracker

In cryptography, the EFF DES cracker (nicknamed "Deep Crack") is a machine built by the Electronic Frontier Foundation (EFF) to perform a brute force search of DES cipher's key space — that is, to decrypt an encrypted message by trying every possible key. The aim in doing this was to prove that DES's key is not long enough to be secure.
The DES uses a 56-bit key, meaning that there are 256 possible keys under which a message can be encrypted. This is approximately 7.21 (more than 72 quadrillion). When DES was approved as a federal standard in 1976, a machine fast enough to test such a number of keys in a reasonable time would have cost an unreasonable amount of money to build.