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perf(crypto): Allow passing points as references to BLS12-381 multi-scalar mul #8818

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perf(crypto): Allow passing points as references to BLS12-381 multi-scalar mul #8818

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78 changes: 70 additions & 8 deletions rs/crypto/internal/crypto_lib/bls12_381/type/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1905,17 +1905,43 @@ macro_rules! declare_muln_vartime_dispatch_for {
}
}

fn muln_vartime_naive(points: &[Self], scalars: &[Scalar]) -> Self {
/// Multiscalar multiplication from references
///
/// Same as `muln_vartime` but accepts points as a slice of references,
/// avoiding the need for callers to clone points into a contiguous `Vec`.
pub fn muln_vartime_ref(points: &[&Self], scalars: &[Scalar]) -> Self {
if points.len() == 1 {
return points[0] * &scalars[0];
} else if points.len() == 2 {
return Self::mul2_vartime(points[0], &scalars[0], points[1], &scalars[1]);
} else if points.len() < $naive_cutoff {
Self::muln_vartime_naive(points, scalars)
} else if points.len() < $w3_cutoff {
Self::muln_vartime_window_3(points, scalars)
} else {
Self::muln_vartime_window_4(points, scalars)
}
}

fn muln_vartime_naive<P: std::borrow::Borrow<Self>>(
points: &[P],
scalars: &[Scalar],
) -> Self {
let (accum, points, scalars) = if points.len() % 2 == 0 {
(Self::identity(), points, scalars)
} else {
(&points[0] * &scalars[0], &points[1..], &scalars[1..])
(
points[0].borrow() * &scalars[0],
&points[1..],
&scalars[1..],
)
};
points
.chunks(2)
.zip(scalars.chunks(2))
.fold(accum, |accum, (c_p, c_s)| {
accum + Self::mul2_vartime(&c_p[0], &c_s[0], &c_p[1], &c_s[1])
accum
+ Self::mul2_vartime(c_p[0].borrow(), &c_s[0], c_p[1].borrow(), &c_s[1])
})
}
}
Expand Down Expand Up @@ -1958,17 +1984,53 @@ macro_rules! declare_muln_affine_vartime_dispatch_for {
}
}

fn muln_affine_vartime_naive(points: &[$affine], scalars: &[Scalar]) -> Self {
/// Multiscalar multiplication from references
///
/// Same as `muln_affine_vartime` but accepts points as a slice of references,
/// avoiding the need for callers to clone points into a contiguous `Vec`.
pub fn muln_affine_vartime_ref(points: &[&$affine], scalars: &[Scalar]) -> Self {
if points.len() == 1 {
return points[0] * &scalars[0];
} else if points.len() == 2 {
return Self::mul2_affine_vartime(
points[0],
&scalars[0],
points[1],
&scalars[1],
);
} else if points.len() < $naive_cutoff {
Self::muln_affine_vartime_naive(points, scalars)
} else if points.len() < $w3_cutoff {
Self::muln_affine_vartime_window_3(points, scalars)
} else {
Self::muln_affine_vartime_window_4(points, scalars)
}
}

fn muln_affine_vartime_naive<P: std::borrow::Borrow<$affine>>(
points: &[P],
scalars: &[Scalar],
) -> Self {
let (accum, points, scalars) = if points.len() % 2 == 0 {
(Self::identity(), points, scalars)
} else {
(&points[0] * &scalars[0], &points[1..], &scalars[1..])
(
points[0].borrow() * &scalars[0],
&points[1..],
&scalars[1..],
)
};
points
.chunks(2)
.zip(scalars.chunks(2))
.fold(accum, |accum, (c_p, c_s)| {
accum + Self::mul2_affine_vartime(&c_p[0], &c_s[0], &c_p[1], &c_s[1])
accum
+ Self::mul2_affine_vartime(
c_p[0].borrow(),
&c_s[0],
c_p[1].borrow(),
&c_s[1],
)
})
}
}
Expand All @@ -1978,7 +2040,7 @@ macro_rules! declare_muln_affine_vartime_dispatch_for {
macro_rules! declare_pippengers_for {
( $typ:ty, $fn_name:ident, $input:ty, $window:expr_2021 ) => {
impl $typ {
fn $fn_name(points: &[$input], scalars: &[Scalar]) -> Self {
fn $fn_name<P: std::borrow::Borrow<$input>>(points: &[P], scalars: &[Scalar]) -> Self {
// Configurable window size: can be in 1..=8
type Window = WindowInfo<$window>;

Expand All @@ -2004,7 +2066,7 @@ macro_rules! declare_pippengers_for {
for j in 0..count {
let bucket_index = windows[j][i] as usize;
if bucket_index > 0 {
buckets[bucket_index] += &points[j];
buckets[bucket_index] += points[j].borrow();
max_bucket = std::cmp::max(max_bucket, bucket_index);
}
}
Expand Down
20 changes: 7 additions & 13 deletions rs/crypto/internal/crypto_lib/threshold_sig/bls12_381/src/ni_dkg/fs_ni_dkg/nizk_chunking.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -279,12 +279,11 @@ pub fn prove_chunking<R: RngCore + CryptoRng>(
let dd = g1.batch_mul(&delta);

let yy = {
let y0_and_pk = [y0.clone()]
.iter()
.chain(&instance.public_keys)
.cloned()
.collect::<Vec<_>>();
G1Projective::muln_affine_vartime(&y0_and_pk, &delta).to_affine()
let y0_and_pk: Vec<_> = [&y0]
.into_iter()
.chain(instance.public_keys.iter())
.collect();
G1Projective::muln_affine_vartime_ref(&y0_and_pk, &delta).to_affine()
};

let second_move = SecondMoveChunking::from(&z_s, &dd, &yy);
Expand Down Expand Up @@ -414,12 +413,7 @@ pub fn verify_chunking(

let cij_to_eijks: Vec<G1Projective> = (0..NUM_ZK_REPETITIONS)
.map(|k| {
let c_ij_s: Vec<_> = instance
.ciphertext_chunks
.iter()
.flatten()
.cloned()
.collect();
let c_ij_s: Vec<_> = instance.ciphertext_chunks.iter().flatten().collect();
let e_ijk_s: Vec<_> = e
.iter()
.flatten()
Expand All @@ -429,7 +423,7 @@ pub fn verify_chunking(
return Err(ZkProofChunkingError::InvalidProof);
}

Ok(G1Projective::muln_affine_vartime(&c_ij_s, &e_ijk_s) + &nizk.cc[k])
Ok(G1Projective::muln_affine_vartime_ref(&c_ij_s, &e_ijk_s) + &nizk.cc[k])
})
.collect::<Result<Vec<_>, _>>()?;

Expand Down
7 changes: 3 additions & 4 deletions rs/crypto/internal/crypto_lib/threshold_sig/bls12_381/src/ni_dkg/fs_ni_dkg/nizk_sharing.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -321,12 +321,11 @@ pub fn verify_sharing(
// The two expressions are re-arranged so that it becomes possible to compute
// everything with a single multi scalar multiplication.

let instance_inputs = instance
let instance_inputs: Vec<_> = instance
.combined_ciphertexts
.iter()
.chain(&instance.public_keys)
.cloned()
.collect::<Vec<G1Affine>>();
.collect();
let challenges = {
let mut c = Vec::with_capacity(xpow.len() * 2);
for xp in &xpow {
Expand All @@ -339,7 +338,7 @@ pub fn verify_sharing(
c
};

let lhs = G1Projective::muln_affine_vartime(&instance_inputs, &challenges);
let lhs = G1Projective::muln_affine_vartime_ref(&instance_inputs, &challenges);
let rhs = &instance.g1_gen.mul_vartime(&nizk.z_alpha) + &nizk.yy.neg();

if lhs != rhs {
Expand Down
12 changes: 6 additions & 6 deletions ...to/internal/crypto_lib/threshold_sig/bls12_381/src/ni_dkg/groth20_bls12_381/transcript.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -211,15 +211,15 @@ fn compute_transcript(
.to_vec()
};

let mut combined = vec![];
let mut combined = Vec::with_capacity(threshold.get() as usize);

for i in 0..threshold.get() as usize {
let points = individual_public_coefficients
.iter()
.map(|pts| pts.1.coefficients[i].0.clone())
.collect::<Vec<_>>();
let points: Vec<_> = individual_public_coefficients
.values()
.map(|pc| &pc.coefficients[i].0)
.collect();
combined.push(crate::types::PublicKey(
G2Projective::muln_affine_vartime(&points, &coefficients).to_affine(),
G2Projective::muln_affine_vartime_ref(&points, &coefficients).to_affine(),
));
}

Expand Down
8 changes: 4 additions & 4 deletions rs/crypto/internal/crypto_lib/threshold_sig/bls12_381/src/types/public_coefficients.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,8 +82,8 @@ impl PublicCoefficients {
) -> Result<G1Projective, ThresholdError> {
let all_x: Vec<NodeIndex> = samples.iter().map(|(x, _)| *x).collect();
let coefficients = Self::lagrange_coefficients_at_zero(&all_x)?;
let pts: Vec<_> = samples.iter().map(|(_, pt)| pt.clone()).collect();
Ok(G1Projective::muln_affine_vartime(&pts, &coefficients))
let pts: Vec<_> = samples.iter().map(|(_, pt)| pt).collect();
Ok(G1Projective::muln_affine_vartime_ref(&pts, &coefficients))
}

/// Given a list of samples `(x, f(x) * g)` for a polynomial `f` in the scalar field, and a generator g of G2 returns
Expand All @@ -98,8 +98,8 @@ impl PublicCoefficients {
) -> Result<G2Projective, ThresholdError> {
let all_x: Vec<NodeIndex> = samples.iter().map(|(x, _)| *x).collect();
let coefficients = Self::lagrange_coefficients_at_zero(&all_x)?;
let pts: Vec<_> = samples.iter().map(|(_, pt)| pt.clone()).collect();
Ok(G2Projective::muln_affine_vartime(&pts, &coefficients))
let pts: Vec<_> = samples.iter().map(|(_, pt)| pt).collect();
Ok(G2Projective::muln_affine_vartime_ref(&pts, &coefficients))
}

/// Compute the Lagrange coefficients at x=0.
Expand Down
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