Round 0 · AddRoundKey
Low byte value
High byte value
Round key (XOR overlay)
This 2D companion lays the AES-128 state flat on a 4×4 grid of byte cells and lets you advance one real cipher operation at a time: the genuine FIPS-197 S-box substitution, the row-wise cyclic shift of ShiftRows, the GF(2⁸) matrix multiplication of MixColumns, and the secret-key XOR of AddRoundKey. Every value shown — the plaintext, the key schedule, the S-box lookups, the finite-field arithmetic — is computed with the real AES-128 algorithm, not a simplified stand-in, so stepping through all 10 rounds reproduces the exact FIPS-197 test-vector ciphertext when you load the example block.