Score:2

Is it possible to adapt Keccak to use 60-bit native words, without having to emulate U64?

ca flag

Assume an architecture with fast 60-bit native words (a close example would be Ocaml, which has unboxed 63-bit numbers, and only boxed 64-bit numbers). We're looking for the fastest hash function in that architecture. Keccak is great, but our best bet, so far, is to port it from implementations that use 32-bit numbers, such as JavaScript. That would be sub-optimal. I wonder if it is possible to modify Keccak to use 60-bit words in its internal states. It would be a different function, but that is fine. Is there any guideline on how to do so safely?

poncho avatar
my flag
Actually, it is known that the Keccak operation modified to have $z=60$ (but otherwise unchanged) is not invertible, that is, not a permutation; I don't know what affect that would have on the security (or how much 'entropy' the nonpermutation would lose)...
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