Pre-Whitening
Pre-whitening XORs the plaintext with an independent key before the first round function, increasing the effective key length.
Purpose
It introduces extra key confusion before the round function, improving resistance to known-plaintext attacks.
Mechanism
ciphertext_pre = plaintext XOR K_pre feeds into the round function, with K_pre independent of the master-key expansion. Twofish uses 128-bit pre-whitening.
Use cases
- Twofish encryption
- Block-cipher hardening
- Effective key-length extension