Implement `BatchNormalize` for `NonIdentity` by daxpedda · Pull Request #1896 · RustCrypto/traits

daxpedda · 2025-06-08T07:39:14Z

As discussed in #1889. I will add some tests in elliptic-curves as well.

Resolves #1889.
Companion PR: RustCrypto/elliptic-curves#1248.

daxpedda · 2025-06-12T09:20:19Z

I completely removed any usage of mem::transmute() and mem::transmute_copy() and opted for safer alternatives.

One notably change: instead of mem::transmute_copy() for fixed arrays, I used array::map(). This seems to be optimized to a memcpy by compilers (Godbolt). Additionally this gets rid of one unsafe call.

tarcieri · 2025-06-13T16:26:50Z

@daxpedda can you also add cargo careful and cargo miri to CI, similar to these?

https://github.com/RustCrypto/crypto-bigint/blob/dff9eb8/.github/workflows/crypto-bigint.yml#L98-L105

https://github.com/RustCrypto/crypto-bigint/blob/dff9eb8/.github/workflows/crypto-bigint.yml#L133-L147

It would also be good to find a way to exercise this code with tests somewhere in this repo, possibly leveraging MockCurve.

tarcieri

Looks good now. I can handle the CI changes as a followup.

daxpedda · 2025-06-13T18:30:54Z

Looks good now. I can handle the CI changes as a followup.

Already on it. Trying to add a test right now.

tarcieri · 2025-06-13T18:43:57Z

+
+        #[allow(unsafe_code)]
+        // SAFETY: `NonIdentity` is `repr(transparent)`.
+        let points: &[P; N] = unsafe { &*points.as_ptr().cast() };


Curious if you could extract an AsRef impl here, but perhaps I can experiment with that myself

Apparently not, because array is a foreign type. Same applies to slices.

I guess we could add it as a method?

* Update to changes in `BatchNormalize` (RustCrypto/traits#1896) * Update to hash2curve changes (RustCrypto/traits#1901)

## Added - Implement `PartialEq + Eq` for `NonIdentity` and `NonZeroScalar` (#1834) - Implement `Zeroize` for `NonIdentity` (#1832) - `NonIdentity::mul_by_generator()` (#1833) - Implement `Mul<&NonZeroScalar>` for `NonIdentity` (#1852) - Implement `Mul<NonIdentity>` for `NonZeroScalar` (#1855) - Expose `AffineCoordinates::y` (#1891) - Scalar macros originall from `primeorder` (#1894) - Implement `BatchNormalize` for `NonIdentity` (#1896) - Re-export `group::Curve` as `CurveGroup` (#1902) - `NonIdentity`/`NonZeroScalar` casting methods (#1903) - `AffineCoordinates::from_coordinates` (#1996) - `getrandom` feature (#2085) - `ctutils` traits to `arithmetic` bounds (#2166) - `Retrieve` bound for `C::Scalar` (#2169) - `crypto_common::Generate` support (#2173, #2208) - Implement `crypto_common::TryKeyInit` for `SecretKey<C>` (#2174) - `dev::bench_projective!` macro (#2177) - Provide `Sec1Point::from/to_sec1_bytes` (#2221) - Implement `From<SecretKey<C>>` for `PublicKey<C>` (#2247) - `SecretKey::diffie_hellman` (#2248) - `LinearCombination::lincomb_vartime` method (#2286) - `ops::MulVartime` trait and bound `Scalar` (#2379) - `ops::MulByGeneratorVartime` trait ([#2381]) - `SecretKey::from_pem` (#2387) - `SecretKey::from_der` (#2408) - `hazmat` module with `FieldArithmetic` trait (#2458) - `Double::double_in_place` (#2464) ## Changed - Migrate from `generic-array` to `hybrid-array` (#1462) - Rename `LinearCombinationExt` => `LinearCombination`; replacing old trait (#1501) - Edition changed to 2024 and MSRV bumped to 1.85 (#1759) - Make `SecretKey::new` fallible (#1804) - Replace `ops::Invert` trait with `crypto_bigint::Invert` (#1839) - Rename `SecretKey::new` => `::from_scalar` (#1893) - Replace `Reduce` trait with `crypto_bigint::Reduce` (#1949) - Bump `serdect` dependency to v0.4 (#1978) - Use `crypto_bigint::Odd` to represent `Curve::ORDER` (#2006) - Bound `Curve::Uint` on `Unsigned` (#2007) - Rename `ScalarPrimitive` => `ScalarValue` (#2008) - Accept mixed-case hex-encoded strings in `FromStr` impl for `ScalarValue` (#2037) - Deprecate `SecretKey::random` (#2086) - Move `MockCurve` to `dev::mock_curve` (#2176) - Bump `rand_core` to v0.10 (#2250) - Rename `EncodedPoint` => `Sec1Point` (#2264) - Bump `crypto-bigint` to v0.7 (#2330) - Bump `digest` to v0.11 (#2331) - Bump `sec1` to v0.8 (#2339) - Bump `hkdf` dependency to v0.13 (#2349) - Use `*Vartime` as a suffix in names (#2378) - Bump `pkcs8` to v0.11 (#2397) - Bump `ff` and `group` to v0.14 (#2430, #2431) - Simplify `BatchInvert` trait (#2455) - Replace `FieldBytesEncoding` trait with `C::FIELD_ENDIANNESS` (#2457) - Move `Double` to `ops` module (#2465) ## Removed - `hazmat` feature (#1599) - `hash2curve` and `oprf` modules: moved to same-name crates (#1929) - PKCS#8 blanket impls for SEC1 private key traits (#1930) - `ShrAssign` bound on `Scalar`s (#1938) - JWK support: migrated to `jose-jwk` crate (#1963) - `weierstrass` module (#2005) - `bits` feature (#2417) ## Fixed - Include curve OID in SEC1 private keys (#1707, #1933)

Implement BatchNormalize for NonIdentity

4c0b1ad

daxpedda mentioned this pull request Jun 8, 2025

Update to changes in BatchNormalize RustCrypto/elliptic-curves#1248

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tarcieri reviewed Jun 11, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs Outdated

tarcieri reviewed Jun 11, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs Outdated

daxpedda added 2 commits June 12, 2025 10:48

Add safety docs

9e1b79e

Remove transmute() calls entirely

e2c3a8f

daxpedda force-pushed the non-identity-batch-normalize branch from 1c8e9df to e2c3a8f Compare June 12, 2025 09:08

daxpedda mentioned this pull request Jun 12, 2025

ACP: add array::from_raw_parts() rust-lang/libs-team#602

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daxpedda commented Jun 12, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs Outdated

daxpedda requested a review from tarcieri June 12, 2025 09:21

tarcieri reviewed Jun 12, 2025

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Comment thread elliptic-curve/src/lib.rs

daxpedda commented Jun 12, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs

Leave comment about why unsafe_code is not forbid

6cda165

daxpedda requested a review from tarcieri June 12, 2025 16:39

daxpedda force-pushed the non-identity-batch-normalize branch 2 times, most recently from 225884b to e3e5f8f Compare June 12, 2025 16:41

Use pointer casting instead of fallible conversion

0a351c7

daxpedda force-pushed the non-identity-batch-normalize branch from e3e5f8f to 0a351c7 Compare June 12, 2025 21:29

tarcieri reviewed Jun 12, 2025

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Comment thread elliptic-curve/src/point.rs

tarcieri reviewed Jun 12, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs Outdated

daxpedda requested a review from tarcieri June 13, 2025 00:12

daxpedda force-pushed the non-identity-batch-normalize branch from 21d93b8 to ced7993 Compare June 13, 2025 00:14

Use pointer casting instead of *::from_raw_parts()

6edc705

daxpedda force-pushed the non-identity-batch-normalize branch from ced7993 to 6edc705 Compare June 13, 2025 00:14

tarcieri reviewed Jun 13, 2025

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Comment thread elliptic-curve/src/point/non_identity.rs Outdated

Compiler is able to optimize away into_iter() + collect()

d9dd703

tarcieri approved these changes Jun 13, 2025

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tarcieri reviewed Jun 13, 2025

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Add BatchNormalize for NonIdentity test

1fd380a

daxpedda requested a review from tarcieri June 13, 2025 18:46

tarcieri merged commit f24c2ae into RustCrypto:master Jun 13, 2025
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tarcieri pushed a commit to RustCrypto/elliptic-curves that referenced this pull request Jun 13, 2025

Update elliptic-curve (#1257)

b9103a6

* Update to changes in `BatchNormalize` (RustCrypto/traits#1896) * Update to hash2curve changes (RustCrypto/traits#1901)

tarcieri mentioned this pull request Jun 23, 2026

elliptic-curve v0.14.0 #2466

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Implement `BatchNormalize` for `NonIdentity`#1896

Implement `BatchNormalize` for `NonIdentity`#1896
tarcieri merged 8 commits into
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daxpedda commented Jun 8, 2025 •

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daxpedda commented Jun 8, 2025 •

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