Keccak-p[1600, 24] permutation's θ step mapping function, which is implemented<br />in terms of 32 -bit word size ( bit interleaved representation )<br /><br />See https://github.com/itzmeanjan/merklize-sha/blob/1d35aae9da7fed20127489f362b4bc93242a516c/include/sha3.hpp#L55-L98 for original implementation<br /><br />Expected stack state :<br /><br />[state_addr, ...]<br /><br />Final stack state :<br /><br />[ ... ]<br /><br />Whole keccak-p[1600, 24] state can be represented using fifty u32 elements i.e. 13 absolute memory addresses<br />s.t. last two elements of 12 -th ( when indexed from zero ) memory address are zeroed.<br /><br />Consecutive memory addresses can be computed by repeated application of `add.1`.<br />
## std::crypto::hashes::keccak256
| Procedure | Description |
| ----------- | ------------- |
| to_bit_interleaved | Given two 32 -bit unsigned integers ( standard form ), representing upper and lower<br />bits of a 64 -bit unsigned integer ( actually a keccak-[1600, 24] lane ),<br />this function converts them into bit interleaved representation, where two 32 -bit<br />unsigned integers ( even portion & then odd portion ) hold bits in even and odd<br />indices of 64 -bit unsigned integer ( remember it's represented in terms of<br />two 32 -bit elements )<br /><br />Input stack state :<br /><br />[hi, lo, ...]<br /><br />After application of bit interleaving, stack looks like<br /><br />[even, odd, ...]<br /><br />Read more about bit interleaved representation in section 2.1 of https://keccak.team/files/Keccak-implementation-3.2.pdf<br /><br />See https://github.com/itzmeanjan/merklize-sha/blob/1d35aae9da7fed20127489f362b4bc93242a516c/include/utils.hpp#L123-L149<br />for reference implementation in higher level language.<br /> |
| from_bit_interleaved | Given two 32 -bit unsigned integers ( in bit interleaved form ), representing even and odd<br />positioned bits of a 64 -bit unsigned integer ( actually a keccak-[1600, 24] lane ),<br />this function converts them into standard representation, where two 32 -bit<br />unsigned integers hold higher ( 32 -bit ) and lower ( 32 -bit ) bits of standard<br />representation of 64 -bit unsigned integer<br /><br />Input stack state :<br /><br />[even, odd, ...]<br /><br />After application of logic, stack looks like<br /><br />[hi, lo, ...]<br /><br />This function reverts the action done by `to_bit_interleaved` function implemented above.<br /><br />Read more about bit interleaved representation in section 2.1 of https://keccak.team/files/Keccak-implementation-3.2.pdf<br /><br />See https://github.com/itzmeanjan/merklize-sha/blob/1d35aae9da7fed20127489f362b4bc93242a516c/include/utils.hpp#L151-L175<br />for reference implementation in higher level language.<br /> |
| hash | Given 64 -bytes input, in terms of sixteen 32 -bit unsigned integers, where each pair<br />of them holding higher & lower 32 -bits of 64 -bit unsigned integer ( reinterpreted on<br />host CPU from little endian byte array ) respectively, this function computes 32 -bytes<br />keccak256 digest, held on stack top, represented in terms of eight 32 -bit unsigned integers,<br />where each pair of them keeps higher and lower 32 -bits of 64 -bit unsigned integer respectively<br /><br />Expected stack state :<br /><br />[iword0, iword1, iword2, iword3, iword4, iword5, iword6, iword7,<br />iword8, iword9, iword10, iword11, iword12, iword13, iword14, iword15, ... ]<br /><br />Final stack state :<br /><br />[oword0, oword1, oword2, oword3, oword4, oword5, oword6, oword7, ... ]<br /><br />See https://github.com/itzmeanjan/merklize-sha/blob/1d35aae9da7fed20127489f362b4bc93242a516c/include/keccak_256.hpp#L232-L257<br /> |