Key Whitening - often only Whitening - is a cryptographic technique by which the security of iterated block ciphers is increased. If you encrypt a plaintext block with Whitening is before the first round of the key associated with parts (pre- whitening ); XOR is used mostly here. Some ciphers use whitening also also after the last round (post - whitening ).
The whitening is mainly used in Feistelchiffren to obscure structures of the clear text and entering the last round and so to increase the complexity of an attack.
- Symmetric Cryptosystem