# [RustCrypto]: NIST P-521 (secp521r1) elliptic curve
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[![Docs][docs-image]][docs-link]
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Pure Rust implementation of the NIST P-521 (a.k.a. secp521r1) elliptic curve.
[Documentation][docs-link]
## ⚠️ 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)][ECDH]: gated under the `ecdh` feature.
- [Elliptic Curve Digital Signature Algorithm (ECDSA)][ECDSA]: gated under the
`ecdsa` feature.
## About P-521
NIST P-521 is a Weierstrass curve specified in [SP 800-186]:
Recommendations for Discrete Logarithm-based Cryptography:
Elliptic Curve Domain Parameters.
Also known as secp521r1 (SECG).
## 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
* [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)
* [MIT license](http://opensource.org/licenses/MIT)
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.
[//]: # (badges)
[crate-image]: https://buildstats.info/crate/p521
[crate-link]: https://crates.io/crates/p521
[docs-image]: https://docs.rs/p521/badge.svg
[docs-link]: https://docs.rs/p521/
[build-image]: https://github.com/RustCrypto/elliptic-curves/actions/workflows/p521.yml/badge.svg
[build-link]: https://github.com/RustCrypto/elliptic-curves/actions/workflows/p521.yml
[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
[rustc-image]: https://img.shields.io/badge/rustc-1.65+-blue.svg
[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260040-elliptic-curves
[//]: # (links)
[RustCrypto]: https://github.com/rustcrypto/
[`elliptic-curve`]: https://github.com/RustCrypto/traits/tree/master/elliptic-curve
[ECDH]: https://en.wikipedia.org/wiki/Elliptic-curve_Diffie-Hellman
[ECDSA]: https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm
[SP 800-186]: https://csrc.nist.gov/publications/detail/sp/800-186/final