# [RustCrypto]: Cryptographic Big Integers

[![crate][crate-image]][crate-link]
[![Docs][docs-image]][docs-link]
[![Build Status][build-image]][build-link]
[![codecov][coverage-image]][coverage-link]
![Apache2/MIT licensed][license-image]
![Rust Version][rustc-image]
[![Project Chat][chat-image]][chat-link]

Pure Rust implementation of a big integer library which has been designed from
the ground-up for use in cryptographic applications.

Provides constant-time, `no_std`-friendly implementations of modern formulas
using const generics.

[Documentation][docs-link]

## Goals

- Supports `no_std`-friendly const generic stack-allocated big integers.
- Constant-time by default. Variable-time functions are explicitly marked as such.
- Leverage what is possible today with const generics on `stable` rust.
- Support `const fn` as much as possible with the goal of being able to compute
  values at compile-time.
- Optional heap-allocated `Boxed*` types gated under an `alloc` feature.

## Security Notes

This crate has been [audited by NCC Group] with no significant
findings. We would like to thank [Entropy] for funding the audit.
Note that the implementation has diverged significantly since the last audit.

All functions contained in the crate are designed to execute in constant
time unless explicitly specified otherwise (via a `*_vartime` name suffix).

This library is NOT suitable for use on processors with a variable-time
multiplication operation (e.g. short circuit on multiply-by-zero /
multiply-by-one, such as certain 32-bit PowerPC CPUs and some non-ARM
microcontrollers).

## Minimum Supported Rust Version (MSRV) Policy

MSRV increases are not considered breaking changes and can happen in patch
releases.

The crate MSRV accounts for all supported targets and crate feature
combinations, excluding explicitly unstable features.

## License

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://img.shields.io/crates/v/crypto-bigint?logo=rust
[crate-link]: https://crates.io/crates/crypto-bigint
[docs-image]: https://docs.rs/crypto-bigint/badge.svg
[docs-link]: https://docs.rs/crypto-bigint/
[build-image]: https://github.com/RustCrypto/crypto-bigint/actions/workflows/crypto-bigint.yml/badge.svg?branch=master
[build-link]: https://github.com/RustCrypto/crypto-bigint/actions/workflows/crypto-bigint.yml?query=branch:master
[coverage-image]: https://codecov.io/gh/RustCrypto/crypto-bigint/graph/badge.svg?token=B4J72KDXXJ
[coverage-link]: https://codecov.io/gh/RustCrypto/crypto-bigint
[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
[rustc-image]: https://img.shields.io/badge/rustc-1.85+-blue.svg
[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/300602-crypto-bigint

[//]: # (links)

[RustCrypto]: https://github.com/rustcrypto
[audited by NCC Group]: https://www.nccgroup.com/us/research-blog/public-report-entropyrust-cryptography-review/
[Entropy]: https://entropy.xyz/
