I was told in passing that (key, plain) pairs could be chosen to produce a zero state in AES encrypt in some middle round (say 5). [The application here being to side-channel leakage assessment.] However, I can't find any reference. I assume such a thing could be constructed from various attacks on reduced-round AES. Does anyone have a reference for the specific question (producing zero state) or for attacks that could be reverse engineered or refactored for this purpose?


1 Answer 1


It's quite easy to find such a key, plaintext pair. All you need to do is:

  • Pick a key, any key

  • Expand the key using the standard AES key expansion process

  • Start with desired block in the middle (e.g. the all 0 block after round 5)

  • Compute the AES transform backwards (that is, in the decrypt direction) from that block

  • The final result is the plaintext block.

I don't expect you'd be able to find a reference to this procedure - it's too obvious to be considered publishable...

  • 2
    $\begingroup$ OK, guess I was overthinking it. The person who said this made it seem like they knew some magic trick. $\endgroup$
    – yoyo
    Dec 7, 2023 at 20:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.