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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”) /// PedersenHashToPoint(“Zcash_PH”, s) + [r]FindGroupHash^J^(r)(“Zcash_PH”, “r”)
/// ///
/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit /// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
pub fn windowed_pedersen_commitment_r<T>( pub fn windowed_pedersen_commitment_r(
csprng: &mut T, rcm: CommitmentRandomness,
s: &BitVec<Lsb0, u8>, s: &BitVec<Lsb0, u8>,
) -> jubjub::ExtendedPoint ) -> jubjub::ExtendedPoint {
where
T: RngCore + CryptoRng,
{
const D: [u8; 8] = *b"Zcash_PH"; const D: [u8; 8] = *b"Zcash_PH";
let mut r_bytes = [0u8; 32]; pedersen_hash_to_point(D, &s) + find_group_hash(D, b"r") * rcm.0
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
} }
/// The randomness used in the Pedersen Hash for note commitment. /// 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 /// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
fn from(note: Note) -> NoteCommitment { fn from(note: Note) -> NoteCommitment {
use rand_core::OsRng;
NoteCommitment::new( NoteCommitment::new(
&mut OsRng, note.rcm,
note.diversifier, note.diversifier,
note.transmission_key, note.transmission_key,
note.value, note.value,
@ -186,15 +177,12 @@ impl NoteCommitment {
/// ///
/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit /// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
#[allow(non_snake_case)] #[allow(non_snake_case)]
pub fn new<T>( pub fn new(
csprng: &mut T, rcm: CommitmentRandomness,
diversifier: Diversifier, diversifier: Diversifier,
transmission_key: TransmissionKey, transmission_key: TransmissionKey,
value: Amount<NonNegative>, value: Amount<NonNegative>,
) -> Self ) -> Self {
where
T: RngCore + CryptoRng,
{
// s as in the argument name for WindowedPedersenCommit_r(s) // s as in the argument name for WindowedPedersenCommit_r(s)
let mut s: BitVec<Lsb0, u8> = BitVec::new(); 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(&pk_d_bytes[..]));
s.append(&mut BitVec::<Lsb0, u8>::from_slice(&v_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 (?) /// Hash Extractor for Jubjub (?)