446 lines
12 KiB
Rust
446 lines
12 KiB
Rust
//! Note and value commitments.
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// #[cfg(test)]
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// mod test_vectors;
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use std::{convert::TryFrom, fmt, io};
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use bitvec::prelude::*;
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use halo2::pasta::pallas;
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use rand_core::{CryptoRng, RngCore};
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use crate::{
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amount::{Amount, NonNegative},
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serialization::{
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serde_helpers, ReadZcashExt, SerializationError, ZcashDeserialize, ZcashSerialize,
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},
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};
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use super::{
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keys::{Diversifier, TransmissionKey},
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sinsemilla::*,
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};
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/// Generates a random scalar from the scalar field 𝔽_{q_P}.
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///
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/// https://zips.z.cash/protocol/nu5.pdf#pallasandvesta
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pub fn generate_trapdoor<T>(csprng: &mut T) -> pallas::Scalar
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where
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T: RngCore + CryptoRng,
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{
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let mut bytes = [0u8; 64];
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csprng.fill_bytes(&mut bytes);
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// Scalar::from_bytes_wide() reduces the input modulo q under the hood.
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pallas::Scalar::from_bytes_wide(&bytes)
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}
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/// The randomness used in the Simsemilla Hash for note commitment.
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#[derive(Copy, Clone, Debug, PartialEq)]
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pub struct CommitmentRandomness(pallas::Scalar);
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/// Note commitments for the output notes.
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#[derive(Clone, Copy, Deserialize, PartialEq, Serialize)]
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pub struct NoteCommitment(#[serde(with = "serde_helpers::Affine")] pub pallas::Affine);
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impl fmt::Debug for NoteCommitment {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_struct("NoteCommitment")
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.field("x", &hex::encode(self.0.get_x().to_bytes()))
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.field("y", &hex::encode(self.0.get_y().to_bytes()))
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.finish()
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}
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}
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impl Eq for NoteCommitment {}
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impl From<pallas::Point> for NoteCommitment {
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fn from(projective_point: pallas::Point) -> Self {
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Self(pallas::Affine::from(projective_point))
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}
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}
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impl From<NoteCommitment> for [u8; 32] {
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fn from(cm: NoteCommitment) -> [u8; 32] {
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cm.0.to_bytes()
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}
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}
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impl TryFrom<[u8; 32]> for NoteCommitment {
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type Error = &'static str;
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fn try_from(bytes: [u8; 32]) -> Result<Self, Self::Error> {
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let possible_point = pallas::Affine::from_bytes(bytes);
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if possible_point.is_some().into() {
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Ok(Self(possible_point.unwrap()))
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} else {
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Err("Invalid pallas::Affine value")
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}
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}
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}
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impl NoteCommitment {
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/// Generate a new _NoteCommitment_ and the randomness used to create it.
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///
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/// We return the randomness because it is needed to construct a _Note_,
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/// before it is encrypted as part of an output of an _Action_. This is a
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/// higher level function that calls `NoteCommit^Orchard_rcm` internally.
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///
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/// NoteCommit^Orchard_rcm(repr_P(gd),repr_P(pkd), v, ρ, ψ) :=
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///
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/// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
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#[allow(non_snake_case)]
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pub fn new<T>(
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csprng: &mut T,
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diversifier: Diversifier,
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transmission_key: TransmissionKey,
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value: Amount<NonNegative>,
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rho: pallas::Base,
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psi: pallas::Base,
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) -> Option<(CommitmentRandomness, Self)>
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where
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T: RngCore + CryptoRng,
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{
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unimplemented!();
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// // s as in the argument name for WindowedPedersenCommit_r(s)
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// let mut s: BitVec<Lsb0, u8> = BitVec::new();
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// // Prefix
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// s.append(&mut bitvec![1; 6]);
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// // The `TryFrom<Diversifier>` impls for the `jubjub::*Point`s handles
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// // calling `DiversifyHash` implicitly.
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// let g_d_bytes: [u8; 32];
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// if let Ok(g_d) = pallas::Affine::try_from(diversifier) {
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// g_d_bytes = g_d.to_bytes();
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// } else {
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// return None;
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// }
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// let pk_d_bytes = <[u8; 32]>::from(transmission_key);
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// let v_bytes = value.to_bytes();
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// s.append(&mut BitVec::<Lsb0, u8>::from_slice(&g_d_bytes[..]));
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// s.append(&mut BitVec::<Lsb0, u8>::from_slice(&pk_d_bytes[..]));
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// s.append(&mut BitVec::<Lsb0, u8>::from_slice(&v_bytes[..]));
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// let rcm = CommitmentRandomness(generate_trapdoor(csprng));
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// Some((
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// rcm,
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// NoteCommitment::from(windowed_pedersen_commitment(rcm.0, &s)),
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// ))
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}
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}
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/// A Homomorphic Pedersen commitment to the value of a note, used in Spend and
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/// Output Descriptions.
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///
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/// https://zips.z.cash/protocol/protocol.pdf#concretehomomorphiccommit
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#[derive(Clone, Copy, Deserialize, PartialEq, Serialize)]
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pub struct ValueCommitment(#[serde(with = "serde_helpers::AffinePoint")] pub pallas::Affine);
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impl<'a> std::ops::Add<&'a ValueCommitment> for ValueCommitment {
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type Output = Self;
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fn add(self, rhs: &'a ValueCommitment) -> Self::Output {
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self + *rhs
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}
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}
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impl std::ops::Add<ValueCommitment> for ValueCommitment {
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type Output = Self;
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fn add(self, rhs: ValueCommitment) -> Self::Output {
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let value = self.0.to_extended() + rhs.0.to_extended();
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ValueCommitment(value.into())
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}
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}
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impl std::ops::AddAssign<ValueCommitment> for ValueCommitment {
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fn add_assign(&mut self, rhs: ValueCommitment) {
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*self = *self + rhs
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}
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}
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impl fmt::Debug for ValueCommitment {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_struct("ValueCommitment")
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.field("x", &hex::encode(self.0.get_x().to_bytes()))
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.field("y", &hex::encode(self.0.get_y().to_bytes()))
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.finish()
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}
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}
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impl From<pallas::Point> for ValueCommitment {
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fn from(projective_point: pallas::Point) -> Self {
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Self(pallas::Affine::from(projective_point))
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}
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}
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impl Eq for ValueCommitment {}
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/// LEBS2OSP256(repr_P(cv))
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///
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/// https://zips.z.cash/protocol/protocol.pdf#pallasandvesta
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impl From<ValueCommitment> for [u8; 32] {
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fn from(cm: ValueCommitment) -> [u8; 32] {
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cm.0.to_bytes()
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}
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}
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impl<'a> std::ops::Sub<&'a ValueCommitment> for ValueCommitment {
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type Output = Self;
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fn sub(self, rhs: &'a ValueCommitment) -> Self::Output {
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self - *rhs
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}
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}
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impl std::ops::Sub<ValueCommitment> for ValueCommitment {
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type Output = Self;
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fn sub(self, rhs: ValueCommitment) -> Self::Output {
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ValueCommitment((self.0.to_extended() - rhs.0.to_extended()).into())
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}
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}
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impl std::ops::SubAssign<ValueCommitment> for ValueCommitment {
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fn sub_assign(&mut self, rhs: ValueCommitment) {
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*self = *self - rhs;
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}
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}
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impl std::iter::Sum for ValueCommitment {
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fn sum<I>(iter: I) -> Self
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where
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I: Iterator<Item = Self>,
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{
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iter.fold(
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ValueCommitment(pallas::Affine::identity()),
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std::ops::Add::add,
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)
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}
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}
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/// LEBS2OSP256(repr_P(cv))
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///
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/// https://zips.z.cash/protocol/protocol.pdf#pallasandvesta
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impl TryFrom<[u8; 32]> for ValueCommitment {
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type Error = &'static str;
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fn try_from(bytes: [u8; 32]) -> Result<Self, Self::Error> {
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let possible_point = pallas::Affine::from_bytes(bytes);
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if possible_point.is_some().into() {
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Ok(Self(possible_point.unwrap()))
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} else {
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Err("Invalid pallas::Affine value")
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}
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}
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}
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impl ZcashSerialize for ValueCommitment {
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fn zcash_serialize<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
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writer.write_all(&<[u8; 32]>::from(*self)[..])?;
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Ok(())
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}
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}
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impl ZcashDeserialize for ValueCommitment {
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fn zcash_deserialize<R: io::Read>(mut reader: R) -> Result<Self, SerializationError> {
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Self::try_from(reader.read_32_bytes()?).map_err(|e| SerializationError::Parse(e))
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}
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}
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impl ValueCommitment {
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/// Generate a new _ValueCommitment_.
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///
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/// https://zips.z.cash/protocol/protocol.pdf#concretehomomorphiccommit
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pub fn randomized<T>(csprng: &mut T, value: Amount) -> Self
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where
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T: RngCore + CryptoRng,
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{
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let rcv = generate_trapdoor(csprng);
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Self::new(rcv, value)
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}
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/// Generate a new _ValueCommitment_ from an existing _rcv_ on a _value_.
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///
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/// ValueCommit^Orchard(v) :=
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///
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/// https://zips.z.cash/protocol/protocol.pdf#concretehomomorphiccommit
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#[allow(non_snake_case)]
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pub fn new(rcv: pallas::Scalar, value: Amount) -> Self {
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let v = pallas::Scalar::from(value);
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// TODO: These generator points can be generated once somewhere else to
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// avoid having to recompute them on every new commitment.
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let V = pallas_group_hash(*b"z.cash:Orchard-cv", b"v");
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let R = pallas_group_hash(*b"z.cash:Orchard-cv", b"r");
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Self::from(V * v + R * rcv)
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}
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}
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#[cfg(test)]
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mod tests {
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use std::ops::Neg;
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use super::*;
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#[test]
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fn sinsemilla_hash_to_point_test_vectors() {
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zebra_test::init();
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const D: [u8; 8] = *b"Zcash_PH";
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for test_vector in test_vectors::TEST_VECTORS.iter() {
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let result =
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pallas::Affine::from(sinsemilla_hash_to_point(D, &test_vector.input_bits.clone()));
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assert_eq!(result, test_vector.output_point);
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}
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}
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// TODO: these test vectors for ops are from Jubjub, replace with Pallas ones
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#[test]
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fn add() {
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zebra_test::init();
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let identity = ValueCommitment(pallas::Affine::identity());
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let g = ValueCommitment(pallas::Affine::from_raw_unchecked(
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pallas::Base::from_raw([
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0xe4b3_d35d_f1a7_adfe,
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0xcaf5_5d1b_29bf_81af,
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0x8b0f_03dd_d60a_8187,
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0x62ed_cbb8_bf37_87c8,
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]),
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pallas::Base::from_raw([
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0x0000_0000_0000_000b,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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]),
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));
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assert_eq!(identity + g, g);
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}
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#[test]
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fn add_assign() {
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zebra_test::init();
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let mut identity = ValueCommitment(pallas::Affine::identity());
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let g = ValueCommitment(pallas::Affine::from_raw_unchecked(
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pallas::Base::from_raw([
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0xe4b3_d35d_f1a7_adfe,
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0xcaf5_5d1b_29bf_81af,
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0x8b0f_03dd_d60a_8187,
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0x62ed_cbb8_bf37_87c8,
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]),
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pallas::Base::from_raw([
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0x0000_0000_0000_000b,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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]),
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));
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identity += g;
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let new_g = identity;
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assert_eq!(new_g, g);
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}
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#[test]
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fn sub() {
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zebra_test::init();
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let g_point = pallas::Affine::from_raw_unchecked(
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pallas::Base::from_raw([
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0xe4b3_d35d_f1a7_adfe,
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0xcaf5_5d1b_29bf_81af,
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0x8b0f_03dd_d60a_8187,
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0x62ed_cbb8_bf37_87c8,
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]),
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pallas::Base::from_raw([
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0x0000_0000_0000_000b,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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]),
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);
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let identity = ValueCommitment(pallas::Affine::identity());
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let g = ValueCommitment(g_point);
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assert_eq!(identity - g, ValueCommitment(g_point.neg()));
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}
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#[test]
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fn sub_assign() {
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zebra_test::init();
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let g_point = pallas::Affine::from_raw_unchecked(
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pallas::Base::from_raw([
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0xe4b3_d35d_f1a7_adfe,
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0xcaf5_5d1b_29bf_81af,
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0x8b0f_03dd_d60a_8187,
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0x62ed_cbb8_bf37_87c8,
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]),
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pallas::Base::from_raw([
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0x0000_0000_0000_000b,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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]),
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);
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let mut identity = ValueCommitment(pallas::Affine::identity());
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let g = ValueCommitment(g_point);
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identity -= g;
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let new_g = identity;
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assert_eq!(new_g, ValueCommitment(g_point.neg()));
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}
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#[test]
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fn sum() {
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zebra_test::init();
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let g_point = pallas::Affine::from_raw_unchecked(
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pallas::Base::from_raw([
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0xe4b3_d35d_f1a7_adfe,
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0xcaf5_5d1b_29bf_81af,
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0x8b0f_03dd_d60a_8187,
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0x62ed_cbb8_bf37_87c8,
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]),
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pallas::Base::from_raw([
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0x0000_0000_0000_000b,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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0x0000_0000_0000_0000,
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]),
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);
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let g = ValueCommitment(g_point);
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let other_g = ValueCommitment(g_point);
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let sum: ValueCommitment = vec![g, other_g].into_iter().sum();
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let doubled_g = ValueCommitment(g_point.to_extended().double().into());
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assert_eq!(sum, doubled_g);
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}
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}
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