# DES-encrypted cipher

Suppose that you knew that a plaintext was encrypted with DES and consisted only of 16-bit Unicode letters, numerals, and punctuation marks available on a standard English-language QWERTY keyboard. How could you use this knowledge to attack the DES-encrypted cipher?

Pure, raw DES has a key length of 56 bits, which makes it trivially vulnerable to a brute-force attack. Just try all $2^{56}$ possible keys to decrypt the message and stop when you find an English message. On average, this will happen after $2^{55}$ trial decryptions. See the Brute Force Attack section on the DES Wikipedia page for more information on how this has been done historically.