mirror of
https://github.com/saymrwulf/anza-cryptography-source.git
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dd4164eefe
* impl secp256r1 * CI * refactor: remove sigantures; add msm * clean up scalar_mul APIs * ci * address comments * CI * fix Eq/PartialEq bug for projective point
125 lines
3.4 KiB
Markdown
125 lines
3.4 KiB
Markdown
# secp256r1
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Pure-Rust secp256r1/P-256 field, scalar, and group operations.
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This crate is scoped to low-level public curve arithmetic for benchmarking,
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experimentation, and syscall plumbing. It does not expose ECDSA signing or
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verification APIs.
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## Status
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This crate is performance-oriented and experimental. It has not been audited.
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Group scalar multiplication APIs are variable time and intended for public
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inputs. Do not use them with secret scalars in environments where local
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timing/cache side channels are in scope.
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Current scope:
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- Base-field arithmetic modulo the P-256 field modulus
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- Scalar-field arithmetic modulo the P-256 group order
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- Affine and Jacobian projective point operations
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- Compressed and uncompressed fixed-length point input
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- Uncompressed fixed-length point output
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- Single-scalar, fixed-base scalar, double-scalar, and multiscalar multiplication
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OpenSSL and `p256` are used only as dev/benchmark comparison dependencies.
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## Installation
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```toml
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[dependencies]
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secp256r1 = { path = "." }
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```
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## API
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```rust
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use secp256r1::{
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group::{AffinePoint, ProjectivePoint},
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scalar::Scalar,
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};
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```
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### Scalar Multiplication
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```rust
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use secp256r1::group::{AffinePoint, ProjectivePoint};
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let scalar = [7u8; 32];
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let fixed_base = ProjectivePoint::fixed_base_scalar_mul_vartime(scalar);
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let variable_base = ProjectivePoint::from_affine(AffinePoint::generator())
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.mul_scalar_vartime(scalar);
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assert_eq!(fixed_base.to_affine(), variable_base.to_affine());
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```
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### Multiscalar Multiplication
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```rust
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use secp256r1::group::{AffinePoint, ProjectivePoint};
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let points = [AffinePoint::generator(), ProjectivePoint::generator().double().to_affine()];
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let scalars = [[7u8; 32], [11u8; 32]];
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let msm = ProjectivePoint::multi_scalar_mul_vartime(&points, &scalars).unwrap();
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let separate = ProjectivePoint::from_affine(points[0]).mul_scalar_vartime(scalars[0])
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+ ProjectivePoint::from_affine(points[1]).mul_scalar_vartime(scalars[1]);
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assert_eq!(msm.to_affine(), separate.to_affine());
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```
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### Encoded Points
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```rust
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use secp256r1::group::{AffinePoint, ProjectivePoint};
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let uncompressed = ProjectivePoint::generator().to_uncompressed().unwrap();
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let parsed = AffinePoint::from_uncompressed(uncompressed).unwrap();
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assert_eq!(parsed, AffinePoint::generator());
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```
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## Benchmarks
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Run all secp256r1 benchmarks:
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```sh
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cargo bench -p secp256r1
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```
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Focused benchmark groups:
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```sh
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cargo bench -p secp256r1 --bench field
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cargo bench -p secp256r1 --bench scalar
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cargo bench -p secp256r1 --bench group
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```
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Representative local results from this workspace:
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### Group Ops
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| Benchmark | rust | p256 | OpenSSL |
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|---|---:|---:|---:|
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| point double | 81.184 ns | 198.83 ns | 222.82 ns public EC |
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| point add | 131.49 ns | 222.38 ns | 216.44 ns public EC |
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| mixed add | 95.753 ns | 195.68 ns | n/a |
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| variable-base scalar mul | 30.579 us | 75.541 us | n/a |
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| fixed-base scalar mul | 3.087 us | n/a | 3.539 us |
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| double scalar mul | 36.716 us | 150.58 us separate | 25.352 us |
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### Multiscalar Multiplication
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| Benchmark | rust MSM | rust separate | p256 separate |
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|---|---:|---:|---:|
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| 8-point MSM | 96.571 us | 244.41 us | 601.21 us |
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| 32-point MSM | 322.63 us | 1.300 ms | 2.410 ms |
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Benchmark numbers are machine- and compiler-dependent. Re-run locally before
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making performance decisions.
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## Safety
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The crate forbids `unsafe` in library code. Benchmark code uses OpenSSL public
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APIs for comparison and is not part of the library.
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