Mix & Key

A Full Round and Honesty

One AES round is visible here, but a deployed cipher call includes more rounds and a mode. This lesson names the boundary.

highlighted = computed this step

What one round contains

This toy view has now shown SubBytes, ShiftRows, MixColumns, and AddRoundKey. Together they form one normal AES round.

four transforms make one round\text{four transforms make one round}
One AES round outputAES state bytes shown as a column-major grid.One AES round output - addroundkeyrowc0c1c2c3r00xa40x680x6b0x02r10x9c0x9f0x5b0x6ar20x7f0x350xea0x50r30xf20x2b0x430x49

What real AES adds

Real AES with 128 runs 10 rounds and derives round keys from a key schedule.

AES with 128: 10 rounds\text{AES with }128:\ 10\ \text{rounds}
One AES round outputAES state bytes shown as a column-major grid.One AES round output - addroundkeyrowc0c1c2c3r00xa40x680x6b0x02r10x9c0x9f0x5b0x6ar20x7f0x350xea0x50r30xf20x2b0x430x49

What this block does not model

This is one block only, not a full encryption mode. NOTE: no-padding; no-side-channel; no-production; never-roll-your-own. Modes, padding, authentication, and side-channel behavior are outside this byte grid.

one block, no mode\text{one block, no mode}
One AES round outputAES state bytes shown as a column-major grid.One AES round output - addroundkeyrowc0c1c2c3r00xa40x680x6b0x02r10x9c0x9f0x5b0x6ar20x7f0x350xea0x50r30xf20x2b0x430x49

Summary

Use reviewed library constructions. NOTE: no-padding; no-side-channel; no-production; never-roll-your-own. Exact byte transforms of ONE AES round over GF(2^8); real AES with 128 runs 10 rounds with a key schedule inside a reviewed mode such as CBC or GCM.

one round only\text{one round only}
One AES round outputAES state bytes shown as a column-major grid.One AES round output - addroundkeyrowc0c1c2c3r00xa40x680x6b0x02r10x9c0x9f0x5b0x6ar20x7f0x350xea0x50r30xf20x2b0x430x49