Key Mixing
Key mixing is the operation of XORing the round key with the data block (AddRoundKey), injecting key material into the round function.
Purpose
It makes each round’s output depend on the round key, giving the key control over the ciphertext, and is a standard round-function component.
Mechanism
The data block is XORed bit-by-bit with the corresponding round key: state = state XOR round_key. XOR’s self-inverse property keeps encryption and decryption symmetric.
Use cases
- AES AddRoundKey
- DES round-key XOR
- Feistel key injection