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Convert more tests to Proptest #809

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3 changes: 2 additions & 1 deletion curve25519-dalek/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,8 @@ sha2 = { version = "0.11.0-rc.2", default-features = false }
bincode = "1"
criterion = { version = "0.5", features = ["html_reports"] }
hex = "0.4.2"
proptest = "1"
proptest = { version = "1", features = ["attr-macro"] }
proptest-derive = "0.6"
rand = "0.9"
rand_core = { version = "0.9", default-features = false, features = ["os_rng"] }

Expand Down
150 changes: 48 additions & 102 deletions curve25519-dalek/src/edwards.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,9 @@ use subtle::ConstantTimeEq;
#[cfg(feature = "zeroize")]
use zeroize::Zeroize;

#[cfg(test)]
use proptest::{arbitrary::Arbitrary, strategy::BoxedStrategy};

use crate::constants;

use crate::field::FieldElement;
Expand Down Expand Up @@ -1771,6 +1774,18 @@ impl CofactorGroup for EdwardsPoint {
}
}

#[cfg(test)]
impl Arbitrary for EdwardsPoint {
type Parameters = ();
type Strategy = BoxedStrategy<Self>;

fn arbitrary_with(_: Self::Parameters) -> Self::Strategy {
use proptest::prelude::*;

Strategy::prop_map(any::<Scalar>(), |scalar| EdwardsPoint::mul_base(&scalar)).boxed()
}
}

// ------------------------------------------------------------------------
// Tests
// ------------------------------------------------------------------------
Expand All @@ -1779,7 +1794,7 @@ impl CofactorGroup for EdwardsPoint {
mod test {
use super::*;

use rand_core::TryRngCore;
use proptest::{prelude::*, property_test};

#[cfg(feature = "alloc")]
use alloc::vec::Vec;
Expand Down Expand Up @@ -2066,17 +2081,14 @@ mod test {
}

/// Check that mul_base_clamped and mul_clamped agree
#[test]
fn mul_base_clamped() {
let mut csprng = rand_core::OsRng;
#[property_test(config = ProptestConfig { cases: 50, .. ProptestConfig::default() })]
fn mul_base_clamped(b: EdwardsPoint, a: [[u8; 32]; 100]) {
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I think this would be better split up into multiple tests, but I didn't know exactly how.

So here is a suggestion, let me know what you think:

    /// Check that mul_base_clamped and mul_clamped agree

    #[test]
    fn mul_base_clamped_max() {
        // Test that mul_base_clamped and mul_clamped agree on a large integer. Even after
        // clamping, this integer is not reduced mod l.
        let a_bytes = [0xff; 32];
        assert_eq!(
            EdwardsPoint::mul_base_clamped(a_bytes),
            constants::ED25519_BASEPOINT_POINT.mul_clamped(a_bytes)
        );
    }

    #[property_test]
    fn mul_base_clamped(a_bytes: [u8; 32]) {
        prop_assert_eq!(
            EdwardsPoint::mul_base_clamped(a_bytes),
            constants::ED25519_BASEPOINT_POINT.mul_clamped(a_bytes)
        );
    }

    #[property_test(config = ProptestConfig { cases: 50, .. ProptestConfig::default() })]
    #[cfg(feature = "precomputed-tables")]
    fn mul_base_clamped_precomputed(b: EdwardsPoint, a_bytes: [u8; 32]) {
        // Make a random curve point in the curve. Give it torsion to make things interesting.
        let random_point = b + constants::EIGHT_TORSION[1];
        // Make a basepoint table from the random point. We'll use this with mul_base_clamped
        let random_table = EdwardsBasepointTableRadix256::create(&random_point);

        prop_assert_eq!(
            random_table.mul_base_clamped(a_bytes),
            random_point.mul_clamped(a_bytes)
        );
    }

#[cfg(not(feature = "precomputed-tables"))]
let _ = b;

// Make a random curve point in the curve. Give it torsion to make things interesting.
#[cfg(feature = "precomputed-tables")]
let random_point = {
let mut b = [0u8; 32];
csprng.try_fill_bytes(&mut b).unwrap();
EdwardsPoint::mul_base_clamped(b) + constants::EIGHT_TORSION[1]
};
let random_point = b + constants::EIGHT_TORSION[1];
// Make a basepoint table from the random point. We'll use this with mul_base_clamped
#[cfg(feature = "precomputed-tables")]
let random_table = EdwardsBasepointTableRadix256::create(&random_point);
Expand All @@ -2086,28 +2098,25 @@ mod test {
// Test that mul_base_clamped and mul_clamped agree on a large integer. Even after
// clamping, this integer is not reduced mod l.
let a_bytes = [0xff; 32];
assert_eq!(
prop_assert_eq!(
EdwardsPoint::mul_base_clamped(a_bytes),
constants::ED25519_BASEPOINT_POINT.mul_clamped(a_bytes)
);
#[cfg(feature = "precomputed-tables")]
assert_eq!(
prop_assert_eq!(
random_table.mul_base_clamped(a_bytes),
random_point.mul_clamped(a_bytes)
);

// Test agreement on random integers
for _ in 0..100 {
for a_bytes in a {
// This will be reduced mod l with probability l / 2^256 ≈ 6.25%
let mut a_bytes = [0u8; 32];
csprng.try_fill_bytes(&mut a_bytes).unwrap();

assert_eq!(
prop_assert_eq!(
EdwardsPoint::mul_base_clamped(a_bytes),
constants::ED25519_BASEPOINT_POINT.mul_clamped(a_bytes)
);
#[cfg(feature = "precomputed-tables")]
assert_eq!(
prop_assert_eq!(
random_table.mul_base_clamped(a_bytes),
random_point.mul_clamped(a_bytes)
);
Expand Down Expand Up @@ -2182,22 +2191,14 @@ mod test {
}
}

#[property_test]
#[cfg(feature = "alloc")]
#[test]
fn compress_batch() {
let mut rng = rand::rng();

// TODO(tarcieri): proptests?
// Make some points deterministically then randomly
let mut points = (1u64..16)
.map(|n| constants::ED25519_BASEPOINT_POINT * Scalar::from(n))
.collect::<Vec<_>>();
points.extend(core::iter::repeat_with(|| EdwardsPoint::random(&mut rng)).take(100));
fn compress_batch(points: Vec<EdwardsPoint>) {
let compressed = EdwardsPoint::compress_batch(&points);

// Check that the batch-compressed points match the individually compressed ones
for (point, compressed) in points.iter().zip(&compressed) {
assert_eq!(&point.compress(), compressed);
prop_assert_eq!(&point.compress(), compressed);
}
}

Expand Down Expand Up @@ -2238,14 +2239,11 @@ mod test {
assert!(P1.compress().to_bytes() == P2.compress().to_bytes());
}

// A single iteration of a consistency check for MSM.
#[property_test]
#[cfg(feature = "alloc")]
fn multiscalar_consistency_iter(n: usize) {
let mut rng = rand::rng();

fn multiscalar_consistency(xs: Vec<Scalar>) {
// Construct random coefficients x0, ..., x_{n-1},
// followed by some extra hardcoded ones.
let xs = (0..n).map(|_| Scalar::random(&mut rng)).collect::<Vec<_>>();
let check = xs.iter().map(|xi| xi * xi).sum::<Scalar>();

// Construct points G_i = x_i * B
Expand All @@ -2258,58 +2256,13 @@ mod test {
// Compute H3 = <xs, Gs> = sum(xi^2) * B
let H3 = EdwardsPoint::mul_base(&check);

assert_eq!(H1, H3);
assert_eq!(H2, H3);
}

// Use different multiscalar sizes to hit different internal
// parameters.

#[test]
#[cfg(feature = "alloc")]
fn multiscalar_consistency_n_100() {
let iters = 50;
for _ in 0..iters {
multiscalar_consistency_iter(100);
}
}

#[test]
#[cfg(feature = "alloc")]
fn multiscalar_consistency_n_250() {
let iters = 50;
for _ in 0..iters {
multiscalar_consistency_iter(250);
}
prop_assert_eq!(H1, H3);
prop_assert_eq!(H2, H3);
}

#[test]
#[property_test]
#[cfg(feature = "alloc")]
fn multiscalar_consistency_n_500() {
let iters = 50;
for _ in 0..iters {
multiscalar_consistency_iter(500);
}
}

#[test]
#[cfg(feature = "alloc")]
fn multiscalar_consistency_n_1000() {
let iters = 50;
for _ in 0..iters {
multiscalar_consistency_iter(1000);
}
}

#[test]
#[cfg(feature = "alloc")]
fn batch_to_montgomery() {
let mut rng = rand::rng();

let scalars = (0..128)
.map(|_| Scalar::random(&mut rng))
.collect::<Vec<_>>();

fn batch_to_montgomery(scalars: Vec<Scalar>) {
let points = scalars
.iter()
.map(EdwardsPoint::mul_base)
Expand All @@ -2320,25 +2273,19 @@ mod test {
.map(EdwardsPoint::to_montgomery)
.collect::<Vec<_>>();

for i in [0, 1, 2, 3, 10, 50, 128] {
let invs = EdwardsPoint::to_montgomery_batch(&points[..i]);
assert_eq!(&invs, &single_monts[..i]);
}
let invs = EdwardsPoint::to_montgomery_batch(&points);
prop_assert_eq!(&invs, &single_monts);
}

#[test]
#[property_test]
#[cfg(feature = "alloc")]
fn vartime_precomputed_vs_nonprecomputed_multiscalar() {
let mut rng = rand::rng();

let static_scalars = (0..128)
.map(|_| Scalar::random(&mut rng))
.collect::<Vec<_>>();

let dynamic_scalars = (0..128)
.map(|_| Scalar::random(&mut rng))
.collect::<Vec<_>>();

fn vartime_precomputed_vs_nonprecomputed_multiscalar(
#[strategy = any::<Vec<Scalar>>().prop_flat_map(|v1| {
let len = v1.len();
(Just(v1), prop::collection::vec(any::<Scalar>(), len))
})]
(static_scalars, dynamic_scalars): (Vec<Scalar>, Vec<Scalar>),
) {
let check_scalar: Scalar = static_scalars
.iter()
.chain(dynamic_scalars.iter())
Expand All @@ -2356,8 +2303,7 @@ mod test {

let precomputation = VartimeEdwardsPrecomputation::new(static_points.iter());

assert_eq!(precomputation.len(), 128);
assert!(!precomputation.is_empty());
prop_assert_eq!(precomputation.len(), static_scalars.len());

let P = precomputation.vartime_mixed_multiscalar_mul(
&static_scalars,
Expand All @@ -2373,8 +2319,8 @@ mod test {

let R = EdwardsPoint::mul_base(&check_scalar);

assert_eq!(P.compress(), R.compress());
assert_eq!(Q.compress(), R.compress());
prop_assert_eq!(P.compress(), R.compress());
prop_assert_eq!(Q.compress(), R.compress());
}

mod vartime {
Expand Down
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