use ark_serialize::{
CanonicalDeserialize, CanonicalDeserializeWithFlags, CanonicalSerialize,
CanonicalSerializeWithFlags, EmptyFlags, Flags, SerializationError,
};
use ark_std::{
cmp::{Ord, Ordering, PartialOrd},
fmt,
io::{Read, Result as IoResult, Write},
marker::PhantomData,
ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign},
vec::Vec,
};
use num_traits::{One, Zero};
use zeroize::Zeroize;
use ark_std::rand::{
distributions::{Distribution, Standard},
Rng,
};
use crate::{
bytes::{FromBytes, ToBytes},
fields::{Field, LegendreSymbol, PrimeField, SquareRootField},
ToConstraintField, UniformRand,
};
pub trait QuadExtParameters: 'static + Send + Sync + Sized {
type BasePrimeField: PrimeField;
type BaseField: Field<BasePrimeField = Self::BasePrimeField>;
type FrobCoeff: Field;
const DEGREE_OVER_BASE_PRIME_FIELD: usize;
const NONRESIDUE: Self::BaseField;
const FROBENIUS_COEFF_C1: &'static [Self::FrobCoeff];
#[inline(always)]
fn mul_base_field_by_nonresidue(fe: &Self::BaseField) -> Self::BaseField {
Self::NONRESIDUE * fe
}
#[inline(always)]
fn add_and_mul_base_field_by_nonresidue(
x: &Self::BaseField,
y: &Self::BaseField,
) -> Self::BaseField {
*x + Self::mul_base_field_by_nonresidue(y)
}
#[inline(always)]
fn add_and_mul_base_field_by_nonresidue_plus_one(
x: &Self::BaseField,
y: &Self::BaseField,
) -> Self::BaseField {
let mut tmp = *x;
tmp += y;
Self::add_and_mul_base_field_by_nonresidue(&tmp, &y)
}
#[inline(always)]
fn sub_and_mul_base_field_by_nonresidue(
x: &Self::BaseField,
y: &Self::BaseField,
) -> Self::BaseField {
*x - Self::mul_base_field_by_nonresidue(y)
}
fn mul_base_field_by_frob_coeff(fe: &mut Self::BaseField, power: usize);
fn cyclotomic_exp(fe: &QuadExtField<Self>, exponent: impl AsRef<[u64]>) -> QuadExtField<Self> {
let mut res = QuadExtField::one();
let mut self_inverse = fe.clone();
self_inverse.conjugate();
let mut found_nonzero = false;
let naf = crate::biginteger::arithmetic::find_wnaf(exponent.as_ref());
for &value in naf.iter().rev() {
if found_nonzero {
res.square_in_place();
}
if value != 0 {
found_nonzero = true;
if value > 0 {
res *= fe;
} else {
res *= &self_inverse;
}
}
}
res
}
}
#[derive(Derivative)]
#[derivative(
Default(bound = "P: QuadExtParameters"),
Hash(bound = "P: QuadExtParameters"),
Clone(bound = "P: QuadExtParameters"),
Copy(bound = "P: QuadExtParameters"),
Debug(bound = "P: QuadExtParameters"),
PartialEq(bound = "P: QuadExtParameters"),
Eq(bound = "P: QuadExtParameters")
)]
pub struct QuadExtField<P: QuadExtParameters> {
pub c0: P::BaseField,
pub c1: P::BaseField,
#[derivative(Debug = "ignore")]
#[doc(hidden)]
pub _parameters: PhantomData<P>,
}
impl<P: QuadExtParameters> QuadExtField<P> {
pub fn new(c0: P::BaseField, c1: P::BaseField) -> Self {
QuadExtField {
c0,
c1,
_parameters: PhantomData,
}
}
pub fn conjugate(&mut self) {
self.c1 = -self.c1;
}
pub fn cyclotomic_exp(&self, exponent: impl AsRef<[u64]>) -> Self {
P::cyclotomic_exp(self, exponent)
}
pub fn norm(&self) -> P::BaseField {
let t0 = self.c0.square();
let mut t1 = self.c1.square();
t1 = P::sub_and_mul_base_field_by_nonresidue(&t0, &t1);
t1
}
pub fn mul_assign_by_basefield(&mut self, element: &P::BaseField) {
self.c0.mul_assign(element);
self.c1.mul_assign(element);
}
}
impl<P: QuadExtParameters> Zero for QuadExtField<P> {
fn zero() -> Self {
QuadExtField::new(P::BaseField::zero(), P::BaseField::zero())
}
fn is_zero(&self) -> bool {
self.c0.is_zero() && self.c1.is_zero()
}
}
impl<P: QuadExtParameters> One for QuadExtField<P> {
fn one() -> Self {
QuadExtField::new(P::BaseField::one(), P::BaseField::zero())
}
fn is_one(&self) -> bool {
self.c0.is_one() && self.c1.is_zero()
}
}
impl<P: QuadExtParameters> Field for QuadExtField<P> {
type BasePrimeField = P::BasePrimeField;
fn extension_degree() -> u64 {
2 * P::BaseField::extension_degree()
}
fn from_base_prime_field_elems(elems: &[Self::BasePrimeField]) -> Option<Self> {
if elems.len() != (Self::extension_degree() as usize) {
return None;
}
let base_ext_deg = P::BaseField::extension_degree() as usize;
Some(Self::new(
P::BaseField::from_base_prime_field_elems(&elems[0..base_ext_deg]).unwrap(),
P::BaseField::from_base_prime_field_elems(&elems[base_ext_deg..]).unwrap(),
))
}
fn double(&self) -> Self {
let mut result = *self;
result.double_in_place();
result
}
fn double_in_place(&mut self) -> &mut Self {
self.c0.double_in_place();
self.c1.double_in_place();
self
}
fn square(&self) -> Self {
let mut result = *self;
result.square_in_place();
result
}
#[inline]
fn from_random_bytes_with_flags<F: Flags>(bytes: &[u8]) -> Option<(Self, F)> {
let split_at = bytes.len() / 2;
if let Some(c0) = P::BaseField::from_random_bytes(&bytes[..split_at]) {
if let Some((c1, flags)) =
P::BaseField::from_random_bytes_with_flags(&bytes[split_at..])
{
return Some((QuadExtField::new(c0, c1), flags));
}
}
None
}
#[inline]
fn from_random_bytes(bytes: &[u8]) -> Option<Self> {
Self::from_random_bytes_with_flags::<EmptyFlags>(bytes).map(|f| f.0)
}
fn square_in_place(&mut self) -> &mut Self {
if P::NONRESIDUE == -P::BaseField::one() {
let c0_copy = self.c0;
let v0 = self.c0 - &self.c1;
self.c1.double_in_place();
self.c0 = v0 + &self.c1;
self.c0 *= &v0;
self.c1 *= &c0_copy;
self
} else {
let mut v0 = self.c0 - &self.c1;
let v3 = P::sub_and_mul_base_field_by_nonresidue(&self.c0, &self.c1);
let v2 = self.c0 * &self.c1;
v0 *= &v3;
self.c1 = v2.double();
self.c0 = P::add_and_mul_base_field_by_nonresidue_plus_one(&v0, &v2);
self
}
}
fn inverse(&self) -> Option<Self> {
if self.is_zero() {
None
} else {
let v1 = self.c1.square();
let v0 = P::sub_and_mul_base_field_by_nonresidue(&self.c0.square(), &v1);
v0.inverse().map(|v1| {
let c0 = self.c0 * &v1;
let c1 = -(self.c1 * &v1);
Self::new(c0, c1)
})
}
}
fn inverse_in_place(&mut self) -> Option<&mut Self> {
if let Some(inverse) = self.inverse() {
*self = inverse;
Some(self)
} else {
None
}
}
fn frobenius_map(&mut self, power: usize) {
self.c0.frobenius_map(power);
self.c1.frobenius_map(power);
P::mul_base_field_by_frob_coeff(&mut self.c1, power);
}
}
impl<'a, P: QuadExtParameters> SquareRootField for QuadExtField<P>
where
P::BaseField: SquareRootField,
{
fn legendre(&self) -> LegendreSymbol {
self.norm().legendre()
}
fn sqrt(&self) -> Option<Self> {
if self.c1.is_zero() {
return self.c0.sqrt().map(|c0| Self::new(c0, P::BaseField::zero()));
}
let alpha = self.norm();
let two_inv = P::BaseField::one()
.double()
.inverse()
.expect("Two should always have an inverse");
alpha.sqrt().and_then(|alpha| {
let mut delta = (alpha + &self.c0) * &two_inv;
if delta.legendre().is_qnr() {
delta -= α
}
let c0 = delta.sqrt().expect("Delta must have a square root");
let c0_inv = c0.inverse().expect("c0 must have an inverse");
let sqrt_cand = Self::new(c0, self.c1 * &two_inv * &c0_inv);
if sqrt_cand.square() == *self {
Some(sqrt_cand)
} else {
#[cfg(debug_assertions)]
{
use crate::fields::LegendreSymbol::*;
if self.legendre() != QuadraticNonResidue {
panic!(
"Input has a square root per its legendre symbol, but it was not found"
)
}
}
None
}
})
}
fn sqrt_in_place(&mut self) -> Option<&mut Self> {
(*self).sqrt().map(|sqrt| {
*self = sqrt;
self
})
}
}
impl<P: QuadExtParameters> Ord for QuadExtField<P> {
#[inline(always)]
fn cmp(&self, other: &Self) -> Ordering {
match self.c1.cmp(&other.c1) {
Ordering::Greater => Ordering::Greater,
Ordering::Less => Ordering::Less,
Ordering::Equal => self.c0.cmp(&other.c0),
}
}
}
impl<P: QuadExtParameters> PartialOrd for QuadExtField<P> {
#[inline(always)]
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<P: QuadExtParameters> Zeroize for QuadExtField<P> {
fn zeroize(&mut self) {
self.c0.zeroize();
self.c1.zeroize();
}
}
impl<P: QuadExtParameters> From<u128> for QuadExtField<P> {
fn from(other: u128) -> Self {
Self::new(other.into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> From<u64> for QuadExtField<P> {
fn from(other: u64) -> Self {
Self::new(other.into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> From<u32> for QuadExtField<P> {
fn from(other: u32) -> Self {
Self::new(other.into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> From<u16> for QuadExtField<P> {
fn from(other: u16) -> Self {
Self::new(other.into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> From<u8> for QuadExtField<P> {
fn from(other: u8) -> Self {
Self::new(other.into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> From<bool> for QuadExtField<P> {
fn from(other: bool) -> Self {
Self::new(u8::from(other).into(), P::BaseField::zero())
}
}
impl<P: QuadExtParameters> ToBytes for QuadExtField<P> {
#[inline]
fn write<W: Write>(&self, mut writer: W) -> IoResult<()> {
self.c0.write(&mut writer)?;
self.c1.write(writer)
}
}
impl<P: QuadExtParameters> FromBytes for QuadExtField<P> {
#[inline]
fn read<R: Read>(mut reader: R) -> IoResult<Self> {
let c0 = P::BaseField::read(&mut reader)?;
let c1 = P::BaseField::read(reader)?;
Ok(QuadExtField::new(c0, c1))
}
}
impl<P: QuadExtParameters> Neg for QuadExtField<P> {
type Output = Self;
#[inline]
#[must_use]
fn neg(mut self) -> Self {
self.c0 = -self.c0;
self.c1 = -self.c1;
self
}
}
impl<P: QuadExtParameters> Distribution<QuadExtField<P>> for Standard {
#[inline]
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> QuadExtField<P> {
QuadExtField::new(UniformRand::rand(rng), UniformRand::rand(rng))
}
}
impl<'a, P: QuadExtParameters> Add<&'a QuadExtField<P>> for QuadExtField<P> {
type Output = Self;
#[inline]
fn add(mut self, other: &Self) -> Self {
self.add_assign(other);
self
}
}
impl<'a, P: QuadExtParameters> Sub<&'a QuadExtField<P>> for QuadExtField<P> {
type Output = Self;
#[inline]
fn sub(mut self, other: &Self) -> Self {
self.sub_assign(other);
self
}
}
impl<'a, P: QuadExtParameters> Mul<&'a QuadExtField<P>> for QuadExtField<P> {
type Output = Self;
#[inline]
fn mul(mut self, other: &Self) -> Self {
self.mul_assign(other);
self
}
}
impl<'a, P: QuadExtParameters> Div<&'a QuadExtField<P>> for QuadExtField<P> {
type Output = Self;
#[inline]
fn div(mut self, other: &Self) -> Self {
self.mul_assign(&other.inverse().unwrap());
self
}
}
impl<'a, P: QuadExtParameters> AddAssign<&'a Self> for QuadExtField<P> {
#[inline]
fn add_assign(&mut self, other: &Self) {
self.c0 += &other.c0;
self.c1 += &other.c1;
}
}
impl<'a, P: QuadExtParameters> SubAssign<&'a Self> for QuadExtField<P> {
#[inline]
fn sub_assign(&mut self, other: &Self) {
self.c0 -= &other.c0;
self.c1 -= &other.c1;
}
}
impl_additive_ops_from_ref!(QuadExtField, QuadExtParameters);
impl_multiplicative_ops_from_ref!(QuadExtField, QuadExtParameters);
impl<'a, P: QuadExtParameters> MulAssign<&'a Self> for QuadExtField<P> {
#[inline]
fn mul_assign(&mut self, other: &Self) {
let v0 = self.c0 * &other.c0;
let v1 = self.c1 * &other.c1;
self.c1 += &self.c0;
self.c1 *= &(other.c0 + &other.c1);
self.c1 -= &v0;
self.c1 -= &v1;
self.c0 = P::add_and_mul_base_field_by_nonresidue(&v0, &v1);
}
}
impl<'a, P: QuadExtParameters> DivAssign<&'a Self> for QuadExtField<P> {
#[inline]
fn div_assign(&mut self, other: &Self) {
self.mul_assign(&other.inverse().unwrap());
}
}
impl<P: QuadExtParameters> fmt::Display for QuadExtField<P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "QuadExtField({} + {} * u)", self.c0, self.c1)
}
}
impl<P: QuadExtParameters> CanonicalSerializeWithFlags for QuadExtField<P> {
#[inline]
fn serialize_with_flags<W: Write, F: Flags>(
&self,
mut writer: W,
flags: F,
) -> Result<(), SerializationError> {
self.c0.serialize(&mut writer)?;
self.c1.serialize_with_flags(&mut writer, flags)?;
Ok(())
}
#[inline]
fn serialized_size_with_flags<F: Flags>(&self) -> usize {
self.c0.serialized_size() + self.c1.serialized_size_with_flags::<F>()
}
}
impl<P: QuadExtParameters> CanonicalSerialize for QuadExtField<P> {
#[inline]
fn serialize<W: Write>(&self, writer: W) -> Result<(), SerializationError> {
self.serialize_with_flags(writer, EmptyFlags)
}
#[inline]
fn serialized_size(&self) -> usize {
self.serialized_size_with_flags::<EmptyFlags>()
}
}
impl<P: QuadExtParameters> CanonicalDeserializeWithFlags for QuadExtField<P> {
#[inline]
fn deserialize_with_flags<R: Read, F: Flags>(
mut reader: R,
) -> Result<(Self, F), SerializationError> {
let c0: P::BaseField = CanonicalDeserialize::deserialize(&mut reader)?;
let (c1, flags): (P::BaseField, _) =
CanonicalDeserializeWithFlags::deserialize_with_flags(&mut reader)?;
Ok((QuadExtField::new(c0, c1), flags))
}
}
impl<P: QuadExtParameters> CanonicalDeserialize for QuadExtField<P> {
#[inline]
fn deserialize<R: Read>(mut reader: R) -> Result<Self, SerializationError> {
let c0: P::BaseField = CanonicalDeserialize::deserialize(&mut reader)?;
let c1: P::BaseField = CanonicalDeserialize::deserialize(&mut reader)?;
Ok(QuadExtField::new(c0, c1))
}
}
impl<P: QuadExtParameters> ToConstraintField<P::BasePrimeField> for QuadExtField<P>
where
P::BaseField: ToConstraintField<P::BasePrimeField>,
{
fn to_field_elements(&self) -> Option<Vec<P::BasePrimeField>> {
let mut res = Vec::new();
let mut c0_elems = self.c0.to_field_elements()?;
let mut c1_elems = self.c1.to_field_elements()?;
res.append(&mut c0_elems);
res.append(&mut c1_elems);
Some(res)
}
}
#[cfg(test)]
mod quad_ext_tests {
use super::*;
use crate::test_field::{Fq, Fq2};
use ark_std::test_rng;
#[test]
fn test_from_base_prime_field_elements() {
let ext_degree = Fq2::extension_degree() as usize;
let max_num_elems_to_test = 4;
for d in 0..max_num_elems_to_test {
if d == ext_degree {
continue;
}
let mut random_coeffs = Vec::<Fq>::new();
for _ in 0..d {
random_coeffs.push(Fq::rand(&mut test_rng()));
}
let res = Fq2::from_base_prime_field_elems(&random_coeffs);
assert_eq!(res, None);
}
let number_of_tests = 10;
for _ in 0..number_of_tests {
let mut random_coeffs = Vec::<Fq>::new();
for _ in 0..ext_degree {
random_coeffs.push(Fq::rand(&mut test_rng()));
}
let actual = Fq2::from_base_prime_field_elems(&random_coeffs).unwrap();
let expected = Fq2::new(random_coeffs[0], random_coeffs[1]);
assert_eq!(actual, expected);
}
}
}