Skip to content

Fix QM31 to not use raw internal value #163

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Sep 26, 2025
Merged

Fix QM31 to not use raw internal value #163

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
3066f02
Fix typo in MAX constant
JulianGCalderon Sep 23, 2025
7d0082b
Use representative instead of to_raw when obtaining QM31 coefficients
JulianGCalderon Sep 23, 2025
df8bfc3
Merge branch 'main' into fix-qm31-packing
JulianGCalderon Sep 24, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
38 changes: 36 additions & 2 deletions crates/starknet-types-core/src/qm31/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,12 @@ impl QM31 {
let [c1, c2] = a.value();
let [c3, c4] = b.value();

(c1.to_raw(), c2.to_raw(), c3.to_raw(), c4.to_raw())
(
c1.representative(),
c2.representative(),
c3.representative(),
c4.representative(),
)
}

/// Packs the [QM31] into a [Felt].
Expand Down Expand Up @@ -208,7 +213,7 @@ mod test {

#[test]
fn qm31_packing() {
const MAX: u32 = MERSENNE_31_PRIME_FIELD_ORDER - 2;
const MAX: u32 = MERSENNE_31_PRIME_FIELD_ORDER - 1;

let cases = [
[1, 2, 3, 4],
Expand Down Expand Up @@ -262,4 +267,33 @@ mod test {

QM31::unpack_from_felt(&invalid_packing).unwrap_err();
}

/// Tests the QM31 packing when some coefficients have a value of PRIME.
///
/// If we try to create an M31 with a value of PRIME, it won't be reduced
/// to 0 internally. This tests verifies that a PRIME coefficient is being
/// packed as its representative value, instead of the raw value.
#[test]
fn qm31_packing_with_prime_coefficients() {
const PRIME: u32 = MERSENNE_31_PRIME_FIELD_ORDER;

let cases = [
[PRIME, 0, 0, 0],
[0, PRIME, 0, 0],
[0, 0, PRIME, 0],
[0, 0, 0, PRIME],
];

for [c1, c2, c3, c4] in cases {
let qm31 = QM31::from_coefficients(c1, c2, c3, c4);
let packed_qm31 = qm31.pack_into_felt();

let expected_packing = BigInt::from(c1 % PRIME)
+ (BigInt::from(c2 % PRIME) << 36)
+ (BigInt::from(c3 % PRIME) << 72)
+ (BigInt::from(c4 % PRIME) << 108);

assert_eq!(packed_qm31, Felt::from(expected_packing))
}
}
}