## Expand description

## RustCrypto: NIST P-256 (secp256r1) elliptic curve

Pure Rust implementation of the NIST P-256 (a.k.a. secp256r1, prime256v1)
elliptic curve with support for ECDH, ECDSA signing/verification, and general
purpose curve arithmetic support implemented in terms of traits from the
`elliptic-curve`

crate.

### ⚠️ Security Warning

The elliptic curve arithmetic contained in this crate has never been independently audited!

This crate has been designed with the goal of ensuring that secret-dependent
operations are performed in constant time (using the `subtle`

crate and
constant-time formulas). However, it has not been thoroughly assessed to ensure
that generated assembly is constant time on common CPU architectures.

USE AT YOUR OWN RISK!

### Supported Algorithms

- Elliptic Curve Diffie-Hellman (ECDH): gated under the
`ecdh`

feature. - Elliptic Curve Digital Signature Algorithm (ECDSA): gated under the
`ecdsa`

feature.

### About NIST P-256

NIST P-256 is a Weierstrass curve specified in SP 800-186: Recommendations for Discrete Logarithm-based Cryptography: Elliptic Curve Domain Parameters.

Also known as prime256v1 (ANSI X9.62) and secp256r1 (SECG), it’s included in the US National Security Agency’s “Suite B” and is widely used in protocols like TLS and the associated X.509 PKI.

### Minimum Supported Rust Version

Rust **1.65** or higher.

Minimum supported Rust version can be changed in the future, but it will be done with a minor version bump.

### SemVer Policy

- All on-by-default features of this library are covered by SemVer
- MSRV is considered exempt from SemVer as noted above

### License

All crates licensed under either of

at your option.

#### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

`serde`

support

When the `serde`

feature of this crate is enabled, `Serialize`

and
`Deserialize`

are impl’d for the following types:

Please see type-specific documentation for more information.

## Re-exports

`pub use elliptic_curve;`

`pub use elliptic_curve::pkcs8;`

## Modules

- ecdh
`ecdh`

Elliptic Curve Diffie-Hellman (Ephemeral) Support. - ecdsa
`ecdsa-core`

Elliptic Curve Digital Signature Algorithm (ECDSA) - test_vectors
`test-vectors`

secp256r1 test vectors.

## Structs

- FieldElement
`arithmetic`

and`expose-field`

An element in the finite field modulo p = 2^{224}(2^{32} − 1) + 2^{192} + 2^{96} − 1. - NIST P-256 elliptic curve.
- Scalar
`arithmetic`

Scalars are elements in the finite field modulo n.

## Type Definitions

- AffinePoint
`arithmetic`

Elliptic curve point in affine coordinates. - BlindedScalar
`arithmetic`

Blinded scalar. - Compressed SEC1-encoded NIST P-256 curve point.
- NIST P-256 SEC1 encoded point.
- NIST P-256 field element serialized as bytes.
- NonZeroScalar
`arithmetic`

Non-zero NIST P-256 scalar field element. - ProjectivePoint
`arithmetic`

Elliptic curve point in projective coordinates. - PublicKey
`arithmetic`

NIST P-256 public key. - ScalarBits
`bits`

Bit representation of a NIST P-256 scalar field element. - NIST P-256 secret key.
- 256-bit unsigned big integer.