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I don't know a lot about cryptography, but I have read a little about it and I've used it in projects. Could someone explain why a 256 bit key seems to crack mo
by jncraton 17y ago
I don't know a lot about cryptography, but I have read a little about it and I've used it in projects. Could someone explain why a 256 bit key seems to crack more easily than a 128 bit key according to this paper? It seems to me that the opposite should be true.
- dfranke 17y agoBecause they're keys to different algorithms. The bit-length in AES is not an arbitrarily tunable parameter. AES-256, AES-192, and AES-128 are related but nonetheless different algorithms. The recent attacks on AES-256 and AES-192 have exploited the key schedules, which is one component that's different between the three algorithms. AES-128's key schedule is better-designed.
- miked 17y agoSchneier responds to that in the comments. It comes down to "key diffusion". Not a crypto guy, but I assume this is basically a matter of statistically distributing the key's properties as evenly and as quickly as possible. In other words, you want the key to die of "heat death" in the cipher text as soon as possible. Because the 256 bit key is longer, it's harder for it to do so. Hence more rounds are needed to further randomize the result.