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Correctly generate a sapling NoteCommitment from the NoteCommitmentRandomness

This commit is contained in:
Deirdre Connolly 2020-07-27 19:11:38 -04:00 committed by Deirdre Connolly
parent b6385ca36f
commit ed888b38ef
1 changed files with 9 additions and 21 deletions
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30
zebra-chain/src/commitments/sapling.rs
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@ -85,20 +85,13 @@ pub fn pedersen_hash(domain: [u8; 8], M: &BitVec<Lsb0, u8>) -> jubjub::Fq {
/// PedersenHashToPoint(“Zcash_PH”, s) + [r]FindGroupHash^J^(r)(“Zcash_PH”, “r”)
///
/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
pub fn windowed_pedersen_commitment_r<T>(
csprng: &mut T,
pub fn windowed_pedersen_commitment_r(
rcm: CommitmentRandomness,
s: &BitVec<Lsb0, u8>,
) -> jubjub::ExtendedPoint
where
T: RngCore + CryptoRng,
{
) -> jubjub::ExtendedPoint {
const D: [u8; 8] = *b"Zcash_PH";
let mut r_bytes = [0u8; 32];
csprng.fill_bytes(&mut r_bytes);
let r = Scalar::from_bytes(&r_bytes).unwrap();
pedersen_hash_to_point(D, &s) + find_group_hash(D, b"r") * r
pedersen_hash_to_point(D, &s) + find_group_hash(D, b"r") * rcm.0
}
/// The randomness used in the Pedersen Hash for note commitment.
@ -150,10 +143,8 @@ impl From<Note> for NoteCommitment {
///
/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
fn from(note: Note) -> NoteCommitment {
use rand_core::OsRng;
NoteCommitment::new(
&mut OsRng,
note.rcm,
note.diversifier,
note.transmission_key,
note.value,
@ -186,15 +177,12 @@ impl NoteCommitment {
///
/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
#[allow(non_snake_case)]
pub fn new<T>(
csprng: &mut T,
pub fn new(
rcm: CommitmentRandomness,
diversifier: Diversifier,
transmission_key: TransmissionKey,
value: Amount<NonNegative>,
) -> Self
where
T: RngCore + CryptoRng,
{
) -> Self {
// s as in the argument name for WindowedPedersenCommit_r(s)
let mut s: BitVec<Lsb0, u8> = BitVec::new();
@ -211,7 +199,7 @@ impl NoteCommitment {
s.append(&mut BitVec::<Lsb0, u8>::from_slice(&pk_d_bytes[..]));
s.append(&mut BitVec::<Lsb0, u8>::from_slice(&v_bytes[..]));
Self::from(windowed_pedersen_commitment_r(csprng, &s))
Self::from(windowed_pedersen_commitment_r(rcm, &s))
}
/// Hash Extractor for Jubjub (?)