Block and state
- AES encrypts a 128-bit block.
- The block is arranged as 16 bytes in a 4 by 4 state matrix.
- All key sizes use the same 128-bit block size.
AES Block Cipher Operation
AES Block Cipher Operation
Trace a 128-bit AES block through real round operations and learner-friendly visual checkpoints
animation
aes
encryption
security
cryptography
interactive
An interactive AES round explorer with real SubBytes, ShiftRows, MixColumns, AddRoundKey, key-size presets, timeline controls, technical accuracy notes, and independent practice prompts.
AES Block Cipher Operation
Follow one 128-bit block as AES repeatedly substitutes bytes, shifts rows, mixes columns, and XORs round keys. The byte values are computed with the real AES operations for the selected test vector, while the interface slows the process down for inspection.
0 / 10Current round
Add keyActive operation
15 / 16Bytes changed
11 round keysKey schedule
TrySelect AES-128, reset the Timeline checkpoint, and press Step until the operation readout reaches MixColumns. Compare the state matrix before and after that step.
ObserveCurrent round and Active operation advance independently, while Bytes changed shows how broadly each transformation alters the 16-byte state. The final round disables MixColumns.
ExplainSubBytes substitutes each byte, ShiftRows permutes positions, MixColumns combines bytes within columns, and AddRoundKey XORs the scheduled key into the state. Their ordered repetition produces diffusion.
Technical boundariesThis is a block-level AES transformation model. It excludes key-generation entropy, timing and power side channels, hardware acceleration, block modes, padding, nonce management, and authentication.
Colour keycryptography identitycurrent / primaryreference / datasuccesscautionerror / failure
AES-128 known-answer block
One 16-byte block is shown as the AES 4 by 4 state matrix. Current checkpoint: initial AddRoundKey.
Before operation
After operation
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--
Block checkpoints
Plaintext
--Round key
--Final ciphertext
--Round Controls
Start with the test vector, then switch key sizes or message profiles. Play advances through the actual AES checkpoint sequence.
Key size presets
Plaintext examples
AES Quick Reference
Round count
- AES-128 uses 10 rounds.
- AES-192 uses 12 rounds.
- AES-256 uses 14 rounds.
Normal round
- SubBytes changes each byte through the S-box.
- ShiftRows rotates row positions.
- MixColumns combines bytes within each column.
- AddRoundKey XORs a round key into the state.
Final round
- The final round still uses SubBytes.
- It still uses ShiftRows.
- It still uses AddRoundKey.
- It skips MixColumns by design.
Technical Accuracy Notes
Real transforms
The visualization computes the AES S-box, row shifts, MixColumns finite-field math, XOR round keys, and key expansion for AES-128, AES-192, and AES-256.
Teaching scope
This page is for learning the sequence and data movement. It is not constant-time code, does not implement modes such as GCM or CBC, and must not be used for production cryptography.
Security context
AES protects confidentiality only when used with an appropriate mode, nonce or IV handling, authentication, key management, and side-channel protections.
IoT relevance
Embedded devices often rely on hardware AES engines because software implementations can leak timing or power information and can be too slow for constrained nodes.
Practice Prompts
Trace a byte
Select SubBytes and note that a byte value changes without moving position. Then select ShiftRows and watch positions move without changing byte values.
Find diffusion
Step to MixColumns. Which columns change together, and why does this make one byte influence multiple later bytes?
Compare key sizes
Switch between AES-128, AES-192, and AES-256. What changes in the number of checkpoints, and what stays the same about the block and state?
Explain final round
Jump to the last round. Confirm that MixColumns is disabled, then describe which operation creates the final ciphertext.