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target/
**/*.rs.bk
Cargo.lock

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[package]
name = "ff"
version = "0.1.0"
authors = ["Sean Bowe <ewillbefull@gmail.com>"]
[dependencies]
rand = "0.3"
ff_derive = { version = "0.1.0", path = "ff_derive" }

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The MIT License (MIT)
Copyright (c) 2017 Sean Bowe
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

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# ff
`ff` is a finite field library written in pure Rust, with no `unsafe{}` code. This library relies on Rust's `i128_type` feature, which is currently only available in the nightly compiler.
## Disclaimers
* This library does not provide constant-time guarantees.
* This library relies on Rust's `i128_type` feature, which is currently only available in the nightly compiler.
## Usage
Add the `ff` crate to your `Cargo.toml`:
```toml
[dependencies]
ff = "0.1"
```
The `ff` crate contains `Field`, `PrimeField`, `PrimeFieldRepr` and `SqrtField` traits. See the **[documentation](http)** 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. It's very easy to use, after you've added it to your `Cargo.toml`.
```rust
extern crate rand;
#[macro_use]
extern crate ff;
#[derive(PrimeField)]
#[PrimeFieldModulus = "57896044618658097711785492504343953926634992332820282019728792003956564819949"]
struct Fp(FpRepr);
```
And that's it! `Fp` now implements `Field` and `PrimeField`. `Fp` will also implement `SqrtField` if supported. The library implements `FpRepr` itself and derives `PrimeFieldRepr` for it.
## 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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[package]
name = "ff_derive"
version = "0.1.0"
authors = ["Sean Bowe <ewillbefull@gmail.com>"]
[lib]
proc-macro = true
[dependencies]
syn = "0.11"
quote = "0.3"
num-bigint = "0.1"
num-traits = "0.1"

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extern crate proc_macro;
//extern crate syn;
//#[macro_use]
extern crate quote;
//extern crate num_bigint;
//extern crate num_traits;
//use num_traits::{Zero, One, ToPrimitive};
//use num_bigint::BigUint;
#[proc_macro_derive(PrimeField, attributes(PrimeFieldModulus))]
pub fn prime_field(
_: proc_macro::TokenStream
) -> proc_macro::TokenStream
{
/*
// Construct a string representation of the type definition
let s = input.to_string();
// Parse the string representation
let ast = syn::parse_derive_input(&s).unwrap();
// The struct we're deriving for is a wrapper around a "Repr" type we must construct.
let repr_ident = fetch_wrapped_ident(&ast.body)
.expect("PrimeField derive only operates over tuple structs of a single item");
// We're given the modulus p of the prime field
let modulus: BigUint = fetch_attr("PrimeFieldModulus", &ast.attrs)
.expect("Please supply a PrimeFieldModulus attribute")
.parse().expect("PrimeFieldModulus should be a number");
// The arithmetic in this library only works if the modulus*2 is smaller than the backing
// representation. Compute the number of limbs we need.
let mut limbs = 1;
{
let mod2 = (&modulus) << 1; // modulus * 2
let mut cur = BigUint::one() << 64;
while cur < mod2 {
limbs += 1;
cur = cur << 64;
}
}
*/
let gen = quote::Tokens::new();
//gen.append(prime_field_repr_impl(&repr_ident, limbs));
//gen.append(prime_field_constants(&repr_ident, modulus, limbs));
//gen.append(prime_field_impl(&ast.ident, &repr_ident));
//gen.append(prime_field_arith_impl(&ast.ident, &repr_ident, limbs));
// Return the generated impl
gen.parse().unwrap()
}
/*
fn fetch_wrapped_ident(
body: &syn::Body
) -> Option<syn::Ident>
{
match body {
&syn::Body::Struct(ref variant_data) => {
let fields = variant_data.fields();
if fields.len() == 1 {
match fields[0].ty {
syn::Ty::Path(_, ref path) => {
if path.segments.len() == 1 {
return Some(path.segments[0].ident.clone());
}
},
_ => {}
}
}
},
_ => {}
};
None
}
/// Fetch an attribute string from the derived struct.
fn fetch_attr(
name: &str,
attrs: &[syn::Attribute]
) -> Option<String>
{
for attr in attrs {
if attr.name() == name {
match attr.value {
syn::MetaItem::NameValue(_, ref val) => {
match val {
&syn::Lit::Str(ref s, _) => {
return Some(s.clone())
},
_ => {
panic!("attribute {} should be a string", name);
}
}
},
_ => {
panic!("attribute {} should be a string", name);
}
}
}
}
None
}
*/

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#![feature(i128_type)]
extern crate rand;
//#[macro_use]
//extern crate ff_derive;
//pub use ff_derive::*;
use std::fmt;
/// This trait represents an element of a field.
pub trait Field: Sized +
Eq +
Copy +
Clone +
Send +
Sync +
fmt::Debug +
'static +
rand::Rand
{
/// Returns the zero element of the field, the additive identity.
fn zero() -> Self;
/// Returns the one element of the field, the multiplicative identity.
fn one() -> Self;
/// Returns true iff this element is zero.
fn is_zero(&self) -> bool;
/// Squares this element.
fn square(&mut self);
/// Doubles this element.
fn double(&mut self);
/// Negates this element.
fn negate(&mut self);
/// Adds another element to this element.
fn add_assign(&mut self, other: &Self);
/// Subtracts another element from this element.
fn sub_assign(&mut self, other: &Self);
/// Multiplies another element by this element.
fn mul_assign(&mut self, other: &Self);
/// Computes the multiplicative inverse of this element, if nonzero.
fn inverse(&self) -> Option<Self>;
/// Exponentiates this element by a power of the modulus.
fn frobenius_map(&mut self, power: usize);
/// Exponentiates this element by a number represented with `u64` limbs,
/// least significant digit first.
fn pow<S: AsRef<[u64]>>(&self, exp: S) -> Self
{
let mut res = Self::one();
for i in BitIterator::new(exp) {
res.square();
if i {
res.mul_assign(self);
}
}
res
}
}
/// This trait represents an element of a field that has a square root operation described for it.
pub trait SqrtField: Field
{
/// Returns the square root of the field element, if it is
/// quadratic residue.
fn sqrt(&self) -> Option<Self>;
}
/// This trait represents a wrapper around a biginteger which can encode any element of a particular
/// prime field. It is a smart wrapper around a sequence of `u64` limbs, least-significant digit
/// first.
pub trait PrimeFieldRepr: Sized +
Copy +
Clone +
Eq +
Ord +
Send +
Sync +
fmt::Debug +
'static +
rand::Rand +
AsRef<[u64]> +
From<u64>
{
/// Subtract another reprensetation from this one. Underflow is ignored.
fn sub_noborrow(&mut self, other: &Self);
/// Add another representation to this one. Overflow is ignored.
fn add_nocarry(&mut self, other: &Self);
/// Compute the number of bits needed to encode this number.
fn num_bits(&self) -> usize;
/// Returns true iff this number is zero.
fn is_zero(&self) -> bool;
/// Returns true iff this number is odd.
fn is_odd(&self) -> bool;
/// Returns true iff this number is even.
fn is_even(&self) -> bool;
/// Performs a rightwise bitshift of this number, effectively dividing
/// it by 2.
fn div2(&mut self);
/// Performs a leftwise bitshift of this number, effectively multiplying
/// it by 2. Overflow is ignored.
fn mul2(&mut self);
}
/// This represents an element of a prime field.
pub trait PrimeField: SqrtField
{
/// The prime field can be converted back and forth into this biginteger
/// representation.
type Repr: PrimeFieldRepr;
/// Convert this prime field element into a biginteger representation.
fn from_repr(Self::Repr) -> Result<Self, ()>;
/// Convert a biginteger reprensentation into a prime field element, if
/// the number is an element of the field.
fn into_repr(&self) -> Self::Repr;
/// Returns the field characteristic; the modulus.
fn char() -> Self::Repr;
/// Returns how many bits are needed to represent an element of this
/// field.
fn num_bits() -> usize;
/// Returns how many bits of information can be reliably stored in the
/// field element.
fn capacity() -> usize;
}
pub struct BitIterator<E> {
t: E,
n: usize
}
impl<E: AsRef<[u64]>> BitIterator<E> {
fn new(t: E) -> Self {
let n = t.as_ref().len() * 64;
BitIterator {
t: t,
n: n
}
}
}
impl<E: AsRef<[u64]>> Iterator for BitIterator<E> {
type Item = bool;
fn next(&mut self) -> Option<bool> {
if self.n == 0 {
None
} else {
self.n -= 1;
let part = self.n / 64;
let bit = self.n - (64 * part);
Some(self.t.as_ref()[part] & (1 << bit) > 0)
}
}
}
#[test]
fn test_bit_iterator() {
let mut a = BitIterator::new([0xa953d79b83f6ab59, 0x6dea2059e200bd39]);
let expected = "01101101111010100010000001011001111000100000000010111101001110011010100101010011110101111001101110000011111101101010101101011001";
for e in expected.chars() {
assert!(a.next().unwrap() == (e == '1'));
}
assert!(a.next().is_none());
let expected = "1010010101111110101010000101101011101000011101110101001000011001100100100011011010001011011011010001011011101100110100111011010010110001000011110100110001100110011101101000101100011100100100100100001010011101010111110011101011000011101000111011011101011001";
let mut a = BitIterator::new([0x429d5f3ac3a3b759, 0xb10f4c66768b1c92, 0x92368b6d16ecd3b4, 0xa57ea85ae8775219]);
for e in expected.chars() {
assert!(a.next().unwrap() == (e == '1'));
}
assert!(a.next().is_none());
}
/// Calculate a - b - borrow, returning the result and modifying
/// the borrow value.
#[inline(always)]
pub fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
let tmp = (1u128 << 64) + (a as u128) - (b as u128) - (*borrow as u128);
*borrow = if tmp >> 64 == 0 { 1 } else { 0 };
tmp as u64
}
/// Calculate a + b + carry, returning the sum and modifying the
/// carry value.
#[inline(always)]
pub fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
let tmp = (a as u128) + (b as u128) + (*carry as u128);
*carry = (tmp >> 64) as u64;
tmp as u64
}
/// Calculate a + (b * c) + carry, returning the least significant digit
/// and setting carry to the most significant digit.
#[inline(always)]
pub fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
let tmp = (a as u128) + (b as u128) * (c as u128) + (*carry as u128);
*carry = (tmp >> 64) as u64;
tmp as u64
}