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# ff
`ff` is a finite field library written in pure Rust, with no `unsafe{}` code.
## Disclaimers
* This library does not provide constant-time guarantees. The traits enable downstream
users to expose constant-time logic, but `#[derive(PrimeField)]` in particular does not
generate constant-time code (even for trait methods that return constant-time-compatible
values).
## Usage
Add the `ff` crate to your `Cargo.toml`:
```toml
[dependencies]
ff = "0.13"
```
The `ff` crate contains the `Field` and `PrimeField` traits.
See the **[documentation](https://docs.rs/ff/)** for more.
### #![derive(PrimeField)]
If you need an implementation of a prime field, this library also provides a procedural
macro that will expand into an efficient implementation of a prime field when supplied
with the modulus. `PrimeFieldGenerator` must be an element of Fp of p-1 order, that is
also quadratic nonresidue.
First, enable the `derive` crate feature:
```toml
[dependencies]
ff = { version = "0.13", features = ["derive"] }
```
And then use the macro like so:
```rust
#[macro_use]
extern crate ff;
#[derive(PrimeField)]
#[PrimeFieldModulus = "52435875175126190479447740508185965837690552500527637822603658699938581184513"]
#[PrimeFieldGenerator = "7"]
#[PrimeFieldReprEndianness = "little"]
struct Fp([u64; 4]);
```
And that's it! `Fp` now implements `Field` and `PrimeField`.
## Minimum Supported Rust Version
Requires Rust **1.56** or higher.
Minimum supported Rust version can be changed in the future, but it will be done with a
minor version bump.
## License
Licensed under either of
* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or 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.
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