The Advanced Encryption Standard (AES) - Understanding Cryptography - page 90

Plaintext

Key

k

x

k

0

Key Addition Layer

Transform 0

Byte Substitution Layer

ShiftRows Layer

round 1 Diffusion Layer

MixColumn Layer

k

1

Key Addition Layer Transform 1

Byte Substitution Layer

ShiftRows Layer

round −1 n r

MixColumn Layer

k n −1

Key Addition Layer

Transform n −1 r

Byte Substitution Layer

last round n ShiftRows Layer

r

k n

r

Key Addition Layer

Transform n

r

Ciphertext

y= AES( ) x

Fig. 4.2 AES encryption block diagram

can add, subtract, multiply and invert. Before we introduce the definition of a field,
we first need the concept of a a simpler algebraic structure, a group.