4 ms·
Has there been any situation in which 10 rounds would be utterly broken but 14 would give you "enough" of a security margin? My impression is that once you've m
by kmeisthax 3y ago
Has there been any situation in which 10 rounds would be utterly broken but 14 would give you "enough" of a security margin? My impression is that once you've managed to break a cipher enough to get that many rounds, you've also discovered a linear-time attack on that cipher[0]. Adding a mere 28% slowdown on that attack won't help.
[0] "Linear time" means O(n), which is computer science speak for "f(n) = an, but we ignore the a because we're only interested in the fastest growing component of the function". In some cases the a is so large as to make the algorithm in question not feasible for ANY size. Let's just pretend the attacker doesn't have that problem.
- nemo1618 3y agoYou'd probably be interested in the "Too Much Crypto" paper linked in the post: https://eprint.iacr.org/2019/1492 https://eprint.iacr.org/2019/1492
- Joker_vD 3y ago> To support this claim, we review the cryptanalysis progress in the last 20 years, ...and rationally and scientifically assuming that the rate of the progress won't increase and that there will be no major breakthroughs in the future, we propose revised number of rounds for AES, BLAKE2, ChaCha, and SHA-3. The crypto is already fast enough, thank you very much; many attacks work only precisely it's quite fast to brute force huge subspaces of key material.
- tptacek 3y agoWhich attacks would those be? Are you thinking about password cracking? What are the other ones?
- tedunangst 3y agoSHA-1 collisions are (almost) as much brute force as anything.
- tptacek 3y agoBut that's not because SHA-1 doesn't have enough rounds; there's a more fundamental flaw in SHA-1.
- tedunangst 3y agoOkay, fair, I hallucinated bits into the statement.
- dragontamer 3y agoIsn't AES completely broken under 5 rounds and currently is considered completely safe at like 8 rounds?
- tedunangst 3y agoSkipjack is notable for having 32 rounds and being broken for 31 rounds.