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Add compute_g() method on Guard and test use_g()

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therealyingtong 2020-09-13 11:47:21 +08:00
parent 1a52d8f6b8
commit 229747e118
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GPG key ID: 179F32A1503D607E
1 changed files with 36 additions and 6 deletions
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42
src/poly/commitment.rs
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@ -269,8 +269,8 @@ impl<'a, C: CurveAffine> Guard<'a, C> {
/// Lets caller supply the challenges and obtain an MSM with updated /// Lets caller supply the challenges and obtain an MSM with updated
/// scalars and points. /// scalars and points.
pub fn use_challenges(mut self) -> MSM<'a, C> { pub fn use_challenges(mut self) -> MSM<'a, C> {
let s = compute_s(&self.challenges_sq, self.allinv * &self.neg_z1); let g = self.compute_g(self.neg_z1);
self.msm.add_to_g(&s); self.msm.add_term(C::Scalar::one(), g);
self.msm self.msm
} }
@ -278,8 +278,7 @@ impl<'a, C: CurveAffine> Guard<'a, C> {
/// Lets caller supply the purported G point and simply appends it to /// Lets caller supply the purported G point and simply appends it to
/// return an updated MSM. /// return an updated MSM.
pub fn use_g(mut self, g: C) -> (MSM<'a, C>, Accumulator<C>) { pub fn use_g(mut self, g: C) -> (MSM<'a, C>, Accumulator<C>) {
&self.msm.other_scalars.push(self.neg_z1); &self.msm.add_term(self.neg_z1, g);
&self.msm.other_bases.push(g);
let accumulator = Accumulator { let accumulator = Accumulator {
g, g,
@ -288,6 +287,30 @@ impl<'a, C: CurveAffine> Guard<'a, C> {
(self.msm, accumulator) (self.msm, accumulator)
} }
/// Computes the g value when given a potential scalar as input.
pub fn compute_g(&self, scalar: C::Scalar) -> C {
let s = compute_s(&self.challenges_sq, self.allinv * &scalar);
let mut g = C::Projective::zero();
if let Some(g_scalars) = &self.msm.g_scalars {
for ((g_scalar, g_base), s) in
g_scalars.iter().zip(self.msm.params.g.iter()).zip(s.iter())
{
// g_base * (g_scalar + s)
let tmp = g_base.mul(*g_scalar + &s);
g = g.add(&tmp);
}
} else {
for (g_base, s) in self.msm.params.g.iter().zip(s.iter()) {
// g_base * (g_scalar + s)
let tmp = g_base.mul(*s);
g = g.add(&tmp);
}
}
g.to_affine()
}
} }
/// Wrapper type around a blinding factor. /// Wrapper type around a blinding factor.
@ -415,9 +438,16 @@ fn test_opening_proof() {
.verify(&params, msm, &mut transcript_dup, x, &p, v) .verify(&params, msm, &mut transcript_dup, x, &p, v)
.unwrap(); .unwrap();
let msm = guard.use_challenges(); // Test use_challenges()
let msm_challenges = guard.clone().use_challenges();
assert!(msm_challenges.is_zero());
// Test use_g()
let g = guard.compute_g(Field::one());
let (msm_g, _accumulator) = guard.clone().use_g(g);
assert!(msm_g.is_zero());
assert!(msm.is_zero());
break; break;
} }
} }