From d0180423c171c0db4902747735e479a2a05414ba Mon Sep 17 00:00:00 2001 From: Deirdre Connolly Date: Thu, 29 Apr 2021 23:37:46 -0400 Subject: [PATCH] Tidy up sinsemilla_hash_to_point() with bitvec --- zebra-chain/src/orchard/sinsemilla.rs | 22 ++++++---------------- 1 file changed, 6 insertions(+), 16 deletions(-) diff --git a/zebra-chain/src/orchard/sinsemilla.rs b/zebra-chain/src/orchard/sinsemilla.rs index 2abefd5f9..4f45e0043 100644 --- a/zebra-chain/src/orchard/sinsemilla.rs +++ b/zebra-chain/src/orchard/sinsemilla.rs @@ -51,12 +51,12 @@ fn Q(D: &[u8]) -> pallas::Point { /// /// https://zips.z.cash/protocol/nu5.pdf#concretesinsemillahash #[allow(non_snake_case)] -fn S(j: &u16) -> pallas::Point { +fn S(j: &BitSlice) -> pallas::Point { // The value of j is a 10-bit value, therefore must never exceed 2^10 in // value. - assert!(j < &1024u16); + assert_eq!(j.len(), 10); - pallas_group_hash(b"z.cash:SinsemillaS", &j.to_le_bytes()) + pallas_group_hash(b"z.cash:SinsemillaS", j.as_slice()) } /// "...an algebraic hash function with collision resistance (for fixed input @@ -87,21 +87,11 @@ pub fn sinsemilla_hash_to_point(D: &[u8], M: &BitVec) -> pallas::Point // https://zips.z.cash/protocol/nu5.pdf#concretesinsemillahash for chunk in M.chunks(k) { // Pad each chunk with zeros. - let mut store = 0u16; + let mut store = [0u8; 2]; let bits = store.bits_mut::(); - chunk - .iter() - .enumerate() - .for_each(|(i, bit)| bits.set(i, *bit)); + bits[..chunk.len()].copy_from_slice(&chunk); - // An instance of LEBS2IP_k - // XXX: does Rust or bitvec have a better implementation? - let j = &bits - .iter() - .enumerate() - .fold(0u16, |j, (i, &bit)| j + if bit { 1 << i } else { 0 }); - - acc = acc + acc + S(j); + acc = acc + acc + S(&bits[..k]); } acc