Hacker News Reader

Comment by swijck | Hacker News Reader

The world changes once you realize why usually encryption is capped at AES256...

256 bit symmetric cryptography keys are a bit like picking one atom in the universe (10^80 atoms, or 100000000000000000000000000000000000000000000000000000000000000000000000000000000). Your opponent would have to test half of the atoms in the universe to have a reasonable chance of getting the right key.

That's generally understood to be not feasible.

https://www.schneier.com/blog/archives/2009/09/the_doghouse_...

It's more than that. Simply incrementing your way through a 256 bit counter is impossible by the thermodynamic cost alone.

Correct. Better to get into other forms of cryptography than pointlessly increase the numbers. We need to think more about PQ proofing.

AES-256 is already post-quantum secure; what exactly are you suggesting?

He could get lucky though. :-P

Care to enlighten us? What did you realize?

It's too CPU heavy and your webservers crash under load would be my guess, for no added benefit [1] of course.

[1] https://security.stackexchange.com/questions/14068/why-most-...

Correct. Anything higher is an order of magnitude more computationally expensive to do for no real reasonable gain. Multiple layers of encryption get you there far enough. Better to dig deeper into other cryptography methods than try increase AES beyond 256. Its already rather insane how quickly decryption happens.

You can trivially modify the AES key schedule to have a key size of any length (ex. replace it with a hash function or a sponge construct) and have any number of increased rounds in the AES permutation. Performance impact will linearly scale with the number of rounds.

You can even have no key schedule at all and just make your AES key size in bits = 128 * num_of_rounds. This doesn't mean that the bruteforce complexity is going to be that high but that would hardly matter...

Hmm, not sure how this was supposed to change my world. I thought you had some secret cabal conspiracy or something to share.

Sorry... I'm boring and easily excited :p

Reply on news.ycombinator.com