Key whitening

In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher.

It consists of steps that combine the data with portions of the key.

DES-X's inventor, Ron Rivest, named the technique whitening.

In a Feistel cipher or similar algorithm, key whitening can increase security by concealing the specific inputs to the first and last round functions.

This form of key whitening has been adopted as a feature of many later block ciphers, including AES, MARS, RC6, and Twofish.