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Fix bug in compute_g()

This commit is contained in:
therealyingtong 2020-09-13 23:10:37 +08:00
parent 1eb2a36086
commit 19ee27e51a
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GPG Key ID: 179F32A1503D607E
1 changed files with 25 additions and 26 deletions
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51
src/poly/commitment.rs
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@ -51,8 +51,11 @@ impl<'a, C: CurveAffine> MSM<'a, C> {
&self.other_bases.push(point);
}
/// Add a vector of scalars to `g_scalars`
/// Add a vector of scalars to `g_scalars`. This function will panic if the
/// caller provides a slice of scalars that is not of length `params.n`.
// TODO: parallelize
pub fn add_to_g(&mut self, scalars: &[C::Scalar]) {
assert_eq!(scalars.len(), self.params.n as usize);
if let Some(g_scalars) = &mut self.g_scalars {
for (g_scalar, scalar) in g_scalars.iter_mut().zip(scalars.iter()) {
*g_scalar += &scalar;
@ -68,6 +71,7 @@ impl<'a, C: CurveAffine> MSM<'a, C> {
}
/// Scale all scalars in the MSM by a random blinding factor
// TODO: parallelize
pub fn scale(&mut self, factor: C::Scalar) {
if let Some(g_scalars) = &mut self.g_scalars {
for g_scalar in g_scalars.iter_mut() {
@ -75,6 +79,7 @@ impl<'a, C: CurveAffine> MSM<'a, C> {
}
}
// TODO: parallelize
for other_scalar in self.other_scalars.iter_mut() {
*other_scalar *= &factor;
}
@ -292,25 +297,7 @@ impl<'a, C: CurveAffine> Guard<'a, C> {
/// 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()
best_multiexp(&s, &self.msm.params.g).to_affine()
}
}
@ -425,7 +412,7 @@ fn test_opening_proof() {
transcript.absorb(Fp::from_bytes(&v.to_bytes()).unwrap()); // unlikely to fail since p ~ q
loop {
let mut transcript_dup = transcript.clone();
let transcript_dup = transcript.clone();
let opening_proof = OpeningProof::create(&params, &mut transcript, &px, blind, x);
if opening_proof.is_err() {
@ -434,18 +421,30 @@ fn test_opening_proof() {
} else {
let opening_proof = opening_proof.unwrap();
// Verify the opening proof
let msm = params.empty_msm();
let guard = opening_proof
.verify(&params, msm, &mut transcript_dup, x, &p, v)
.verify(
&params,
params.empty_msm(),
&mut transcript_dup.clone(),
x,
&p,
v,
)
.unwrap();
// Generate a `new_guard` to populate `msm.g_scalars`
let msm = guard.use_challenges();
let new_guard = opening_proof
.verify(&params, msm, &mut transcript_dup.clone(), x, &p, v)
.unwrap();
// Test use_challenges()
let msm_challenges = guard.clone().use_challenges();
let msm_challenges = new_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);
let g = new_guard.compute_g(Field::one());
let (msm_g, _accumulator) = new_guard.clone().use_g(g);
assert!(msm_g.is_zero());