158 lines
4.8 KiB
Rust
158 lines
4.8 KiB
Rust
//! Signature types for the Orchard protocol.
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#[cfg(feature = "alloc")]
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use alloc::vec::Vec;
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#[cfg(feature = "alloc")]
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use core::borrow::Borrow;
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use group::GroupEncoding;
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#[cfg(feature = "alloc")]
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use group::{ff::PrimeField, Group};
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use pasta_curves::pallas;
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use crate::{private, SigType};
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#[cfg(feature = "alloc")]
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use crate::scalar_mul::{LookupTable5, NonAdjacentForm, VartimeMultiscalarMul};
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#[cfg(test)]
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mod tests;
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/// The byte-encoding of the basepoint for the Orchard `SpendAuthSig` on the [Pallas curve][pallasandvesta].
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///
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/// [pallasandvesta]: https://zips.z.cash/protocol/nu5.pdf#pallasandvesta
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// Reproducible by pallas::Point::hash_to_curve("z.cash:Orchard")(b"G").to_bytes()
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const ORCHARD_SPENDAUTHSIG_BASEPOINT_BYTES: [u8; 32] = [
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99, 201, 117, 184, 132, 114, 26, 141, 12, 161, 112, 123, 227, 12, 127, 12, 95, 68, 95, 62, 124,
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24, 141, 59, 6, 214, 241, 40, 179, 35, 85, 183,
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];
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/// The byte-encoding of the basepoint for the Orchard `BindingSig` on the Pallas curve.
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// Reproducible by pallas::Point::hash_to_curve("z.cash:Orchard-cv")(b"r").to_bytes()
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const ORCHARD_BINDINGSIG_BASEPOINT_BYTES: [u8; 32] = [
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145, 90, 60, 136, 104, 198, 195, 14, 47, 128, 144, 238, 69, 215, 110, 64, 72, 32, 141, 234, 91,
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35, 102, 79, 187, 9, 164, 15, 85, 68, 244, 7,
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];
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/// A type variable corresponding to Zcash's `OrchardSpendAuthSig`.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum SpendAuth {}
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// This should not exist, but is necessary to use zeroize::DefaultIsZeroes.
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impl Default for SpendAuth {
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fn default() -> Self {
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unimplemented!()
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}
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}
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impl SigType for SpendAuth {}
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impl super::SpendAuth for SpendAuth {}
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/// A type variable corresponding to Zcash's `OrchardBindingSig`.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum Binding {}
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// This should not exist, but is necessary to use zeroize::DefaultIsZeroes.
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impl Default for Binding {
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fn default() -> Self {
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unimplemented!()
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}
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}
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impl SigType for Binding {}
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impl super::Binding for Binding {}
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impl private::SealedScalar for pallas::Scalar {
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fn from_bytes_wide(bytes: &[u8; 64]) -> Self {
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<pallas::Scalar as group::ff::FromUniformBytes<64>>::from_uniform_bytes(bytes)
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}
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fn from_raw(val: [u64; 4]) -> Self {
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pallas::Scalar::from_raw(val)
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}
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}
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impl private::Sealed<SpendAuth> for SpendAuth {
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const H_STAR_PERSONALIZATION: &'static [u8; 16] = b"Zcash_RedPallasH";
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type Point = pallas::Point;
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type Scalar = pallas::Scalar;
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fn basepoint() -> pallas::Point {
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pallas::Point::from_bytes(&ORCHARD_SPENDAUTHSIG_BASEPOINT_BYTES).unwrap()
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}
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}
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impl private::Sealed<Binding> for Binding {
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const H_STAR_PERSONALIZATION: &'static [u8; 16] = b"Zcash_RedPallasH";
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type Point = pallas::Point;
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type Scalar = pallas::Scalar;
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fn basepoint() -> pallas::Point {
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pallas::Point::from_bytes(&ORCHARD_BINDINGSIG_BASEPOINT_BYTES).unwrap()
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}
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}
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#[cfg(feature = "alloc")]
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impl NonAdjacentForm for pallas::Scalar {
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fn inner_to_bytes(&self) -> [u8; 32] {
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self.to_repr()
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}
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/// The NAF length for Pallas is 255 since Pallas' order is about 2<sup>254</sup> +
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/// 2<sup>125.1</sup>.
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fn naf_length() -> usize {
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255
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}
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}
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#[cfg(feature = "alloc")]
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impl<'a> From<&'a pallas::Point> for LookupTable5<pallas::Point> {
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#[allow(non_snake_case)]
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fn from(A: &'a pallas::Point) -> Self {
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let mut Ai = [*A; 8];
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let A2 = A.double();
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for i in 0..7 {
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Ai[i + 1] = A2 + Ai[i];
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}
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// Now Ai = [A, 3A, 5A, 7A, 9A, 11A, 13A, 15A]
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LookupTable5(Ai)
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}
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}
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#[cfg(feature = "alloc")]
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impl VartimeMultiscalarMul for pallas::Point {
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type Scalar = pallas::Scalar;
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type Point = pallas::Point;
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#[allow(non_snake_case)]
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fn optional_multiscalar_mul<I, J>(scalars: I, points: J) -> Option<pallas::Point>
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where
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I: IntoIterator,
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I::Item: Borrow<Self::Scalar>,
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J: IntoIterator<Item = Option<pallas::Point>>,
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{
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let nafs: Vec<_> = scalars
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.into_iter()
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.map(|c| c.borrow().non_adjacent_form(5))
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.collect();
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let lookup_tables = points
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.into_iter()
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.map(|P_opt| P_opt.map(|P| LookupTable5::<pallas::Point>::from(&P)))
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.collect::<Option<Vec<_>>>()?;
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let mut r = pallas::Point::identity();
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let naf_size = Self::Scalar::naf_length();
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for i in (0..naf_size).rev() {
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let mut t = r.double();
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for (naf, lookup_table) in nafs.iter().zip(lookup_tables.iter()) {
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#[allow(clippy::comparison_chain)]
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if naf[i] > 0 {
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t += lookup_table.select(naf[i] as usize);
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} else if naf[i] < 0 {
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t -= lookup_table.select(-naf[i] as usize);
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}
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}
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r = t;
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}
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Some(r)
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}
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}
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