plonky2/evm/src/extension_tower.rs
2024-01-09 09:33:17 +00:00

1322 lines
32 KiB
Rust

use std::fmt::Debug;
use std::ops::{Add, Div, Mul, Neg, Sub};
use ethereum_types::{U256, U512};
use rand::distributions::{Distribution, Standard};
use rand::Rng;
pub trait FieldExt:
Copy
+ std::fmt::Debug
+ std::cmp::PartialEq
+ std::ops::Add<Output = Self>
+ std::ops::Neg<Output = Self>
+ std::ops::Sub<Output = Self>
+ std::ops::Mul<Output = Self>
+ std::ops::Div<Output = Self>
{
const ZERO: Self;
const UNIT: Self;
fn new(val: usize) -> Self;
fn inv(self) -> Self;
}
pub(crate) const BN_BASE: U256 = U256([
0x3c208c16d87cfd47,
0x97816a916871ca8d,
0xb85045b68181585d,
0x30644e72e131a029,
]);
#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) struct BN254 {
pub val: U256,
}
impl Distribution<BN254> for Standard {
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> BN254 {
let xs = rng.gen::<[u64; 4]>();
BN254 {
val: U256(xs) % BN_BASE,
}
}
}
impl Add for BN254 {
type Output = Self;
fn add(self, other: Self) -> Self {
BN254 {
val: (self.val + other.val) % BN_BASE,
}
}
}
impl Neg for BN254 {
type Output = Self;
fn neg(self) -> Self::Output {
BN254 {
val: (BN_BASE - self.val) % BN_BASE,
}
}
}
impl Sub for BN254 {
type Output = Self;
fn sub(self, other: Self) -> Self {
BN254 {
val: (BN_BASE + self.val - other.val) % BN_BASE,
}
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl Mul for BN254 {
type Output = Self;
fn mul(self, other: Self) -> Self {
BN254 {
val: U256::try_from((self.val).full_mul(other.val) % BN_BASE).unwrap(),
}
}
}
impl FieldExt for BN254 {
const ZERO: Self = BN254 { val: U256::zero() };
const UNIT: Self = BN254 { val: U256::one() };
fn new(val: usize) -> BN254 {
BN254 {
val: U256::from(val),
}
}
fn inv(self) -> BN254 {
let exp = BN_BASE - 2;
let mut current = self;
let mut product = BN254 { val: U256::one() };
for j in 0..256 {
if exp.bit(j) {
product = product * current;
}
current = current * current;
}
product
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl Div for BN254 {
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inv()
}
}
pub(crate) const BLS_BASE: U512 = U512([
0xb9feffffffffaaab,
0x1eabfffeb153ffff,
0x6730d2a0f6b0f624,
0x64774b84f38512bf,
0x4b1ba7b6434bacd7,
0x1a0111ea397fe69a,
0x0,
0x0,
]);
#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) struct BLS381 {
pub val: U512,
}
impl BLS381 {
pub(crate) fn lo(self) -> U256 {
U256(self.val.0[..4].try_into().unwrap())
}
pub(crate) fn hi(self) -> U256 {
U256(self.val.0[4..].try_into().unwrap())
}
}
impl Distribution<BLS381> for Standard {
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> BLS381 {
let xs = rng.gen::<[u64; 8]>();
BLS381 {
val: U512(xs) % BLS_BASE,
}
}
}
impl Add for BLS381 {
type Output = Self;
fn add(self, other: Self) -> Self {
BLS381 {
val: (self.val + other.val) % BLS_BASE,
}
}
}
impl Neg for BLS381 {
type Output = Self;
fn neg(self) -> Self::Output {
BLS381 {
val: (BLS_BASE - self.val) % BLS_BASE,
}
}
}
impl Sub for BLS381 {
type Output = Self;
fn sub(self, other: Self) -> Self {
BLS381 {
val: (BLS_BASE + self.val - other.val) % BLS_BASE,
}
}
}
impl BLS381 {
fn lsh_128(self) -> BLS381 {
let b128: U512 = U512([0, 0, 1, 0, 0, 0, 0, 0]);
// since BLS_BASE < 2^384, multiplying by 2^128 doesn't overflow the U512
BLS381 {
val: self.val.saturating_mul(b128) % BLS_BASE,
}
}
fn lsh_256(self) -> BLS381 {
self.lsh_128().lsh_128()
}
fn lsh_512(self) -> BLS381 {
self.lsh_256().lsh_256()
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl Mul for BLS381 {
type Output = Self;
fn mul(self, other: Self) -> Self {
// x1, y1 are at most ((q-1) // 2^256) < 2^125
let x0 = U512::from(self.lo());
let x1 = U512::from(self.hi());
let y0 = U512::from(other.lo());
let y1 = U512::from(other.hi());
let z00 = BLS381 {
val: x0.saturating_mul(y0) % BLS_BASE,
};
let z01 = BLS381 {
val: x0.saturating_mul(y1),
};
let z10 = BLS381 {
val: x1.saturating_mul(y0),
};
let z11 = BLS381 {
val: x1.saturating_mul(y1),
};
z00 + (z01 + z10).lsh_256() + z11.lsh_512()
}
}
impl FieldExt for BLS381 {
const ZERO: Self = BLS381 { val: U512::zero() };
const UNIT: Self = BLS381 { val: U512::one() };
fn new(val: usize) -> BLS381 {
BLS381 {
val: U512::from(val),
}
}
fn inv(self) -> BLS381 {
let exp = BLS_BASE - 2;
let mut current = self;
let mut product = BLS381 { val: U512::one() };
for j in 0..512 {
if exp.bit(j) {
product = product * current;
}
current = current * current;
}
product
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl Div for BLS381 {
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inv()
}
}
/// The degree 2 field extension Fp2 is given by adjoining i, the square root of -1, to BN254
/// The arithmetic in this extension is standard complex arithmetic
#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) struct Fp2<T>
where
T: FieldExt,
{
pub re: T,
pub im: T,
}
impl<T> Distribution<Fp2<T>> for Standard
where
T: FieldExt,
Standard: Distribution<T>,
{
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Fp2<T> {
let (re, im) = rng.gen::<(T, T)>();
Fp2 { re, im }
}
}
impl<T: FieldExt> Add for Fp2<T> {
type Output = Self;
fn add(self, other: Self) -> Self {
Fp2 {
re: self.re + other.re,
im: self.im + other.im,
}
}
}
impl<T: FieldExt> Neg for Fp2<T> {
type Output = Self;
fn neg(self) -> Self::Output {
Fp2 {
re: -self.re,
im: -self.im,
}
}
}
impl<T: FieldExt> Sub for Fp2<T> {
type Output = Self;
fn sub(self, other: Self) -> Self {
Fp2 {
re: self.re - other.re,
im: self.im - other.im,
}
}
}
impl<T: FieldExt> Mul for Fp2<T> {
type Output = Self;
fn mul(self, other: Self) -> Self {
Fp2 {
re: self.re * other.re - self.im * other.im,
im: self.re * other.im + self.im * other.re,
}
}
}
/// This function scalar multiplies an Fp2 by an Fp
impl<T: FieldExt> Mul<T> for Fp2<T> {
type Output = Fp2<T>;
fn mul(self, other: T) -> Self {
Fp2 {
re: other * self.re,
im: other * self.im,
}
}
}
impl<T: FieldExt> Fp2<T> {
/// Return the complex conjugate z' of z: Fp2
/// This also happens to be the frobenius map
/// z -> z^p
/// since p == 3 mod 4 and hence
/// i^p = i^(4k) * i^3 = 1*(-i) = -i
fn conj(self) -> Self {
Fp2 {
re: self.re,
im: -self.im,
}
}
// Return the magnitude squared of a complex number
fn norm_sq(self) -> T {
self.re * self.re + self.im * self.im
}
}
impl<T: FieldExt> FieldExt for Fp2<T> {
const ZERO: Fp2<T> = Fp2 {
re: T::ZERO,
im: T::ZERO,
};
const UNIT: Fp2<T> = Fp2 {
re: T::UNIT,
im: T::ZERO,
};
fn new(val: usize) -> Fp2<T> {
Fp2 {
re: T::new(val),
im: T::ZERO,
}
}
/// The inverse of z is given by z'/||z||^2 since ||z||^2 = zz'
fn inv(self) -> Fp2<T> {
let norm_sq = self.norm_sq();
self.conj() * norm_sq.inv()
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl<T: FieldExt> Div for Fp2<T> {
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inv()
}
}
/// This trait defines the method which multiplies
/// by the Fp2 element t^3 whose cube root we will
/// adjoin in the subsequent cubic extension.
/// For BN254 this is 9+i, and for BLS381 it is 1+i.
/// It also defines the relevant FROB constants,
/// given by t^(p^n) and t^(p^2n) for various n,
/// used to compute the frobenius operations.
pub trait Adj: Sized {
fn mul_adj(self) -> Self;
const FROB_T: [[Self; 6]; 2];
const FROB_Z: [Self; 12];
}
impl Adj for Fp2<BN254> {
fn mul_adj(self) -> Self {
let nine = BN254::new(9);
Fp2 {
re: nine * self.re - self.im,
im: self.re + nine * self.im,
}
}
const FROB_T: [[Fp2<BN254>; 6]; 2] = [
[
Fp2 {
re: BN254 { val: U256::one() },
im: BN254 { val: U256::zero() },
},
Fp2 {
re: BN254 {
val: U256([
0x99e39557176f553d,
0xb78cc310c2c3330c,
0x4c0bec3cf559b143,
0x2fb347984f7911f7,
]),
},
im: BN254 {
val: U256([
0x1665d51c640fcba2,
0x32ae2a1d0b7c9dce,
0x4ba4cc8bd75a0794,
0x16c9e55061ebae20,
]),
},
},
Fp2 {
re: BN254 {
val: U256([
0xe4bd44e5607cfd48,
0xc28f069fbb966e3d,
0x5e6dd9e7e0acccb0,
0x30644e72e131a029,
]),
},
im: BN254 { val: U256::zero() },
},
Fp2 {
re: BN254 {
val: U256([
0x7b746ee87bdcfb6d,
0x805ffd3d5d6942d3,
0xbaff1c77959f25ac,
0x0856e078b755ef0a,
]),
},
im: BN254 {
val: U256([
0x380cab2baaa586de,
0x0fdf31bf98ff2631,
0xa9f30e6dec26094f,
0x04f1de41b3d1766f,
]),
},
},
Fp2 {
re: BN254 {
val: U256([
0x5763473177fffffe,
0xd4f263f1acdb5c4f,
0x59e26bcea0d48bac,
0x0,
]),
},
im: BN254 { val: U256::zero() },
},
Fp2 {
re: BN254 {
val: U256([
0x62e913ee1dada9e4,
0xf71614d4b0b71f3a,
0x699582b87809d9ca,
0x28be74d4bb943f51,
]),
},
im: BN254 {
val: U256([
0xedae0bcec9c7aac7,
0x54f40eb4c3f6068d,
0xc2b86abcbe01477a,
0x14a88ae0cb747b99,
]),
},
},
],
[
Fp2 {
re: BN254 { val: U256::one() },
im: BN254 { val: U256::zero() },
},
Fp2 {
re: {
BN254 {
val: U256([
0x848a1f55921ea762,
0xd33365f7be94ec72,
0x80f3c0b75a181e84,
0x05b54f5e64eea801,
]),
}
},
im: {
BN254 {
val: U256([
0xc13b4711cd2b8126,
0x3685d2ea1bdec763,
0x9f3a80b03b0b1c92,
0x2c145edbe7fd8aee,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0x5763473177fffffe,
0xd4f263f1acdb5c4f,
0x59e26bcea0d48bac,
0x0,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0x0e1a92bc3ccbf066,
0xe633094575b06bcb,
0x19bee0f7b5b2444e,
0xbc58c6611c08dab,
]),
}
},
im: {
BN254 {
val: U256([
0x5fe3ed9d730c239f,
0xa44a9e08737f96e5,
0xfeb0f6ef0cd21d04,
0x23d5e999e1910a12,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0xe4bd44e5607cfd48,
0xc28f069fbb966e3d,
0x5e6dd9e7e0acccb0,
0x30644e72e131a029,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0xa97bda050992657f,
0xde1afb54342c724f,
0x1d9da40771b6f589,
0x1ee972ae6a826a7d,
]),
}
},
im: {
BN254 {
val: U256([
0x5721e37e70c255c9,
0x54326430418536d1,
0xd2b513cdbb257724,
0x10de546ff8d4ab51,
]),
}
},
},
],
];
const FROB_Z: [Fp2<BN254>; 12] = [
Fp2 {
re: { BN254 { val: U256::one() } },
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0xd60b35dadcc9e470,
0x5c521e08292f2176,
0xe8b99fdd76e68b60,
0x1284b71c2865a7df,
]),
}
},
im: {
BN254 {
val: U256([
0xca5cf05f80f362ac,
0x747992778eeec7e5,
0xa6327cfe12150b8e,
0x246996f3b4fae7e6,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0xe4bd44e5607cfd49,
0xc28f069fbb966e3d,
0x5e6dd9e7e0acccb0,
0x30644e72e131a029,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0xe86f7d391ed4a67f,
0x894cb38dbe55d24a,
0xefe9608cd0acaa90,
0x19dc81cfcc82e4bb,
]),
}
},
im: {
BN254 {
val: U256([
0x7694aa2bf4c0c101,
0x7f03a5e397d439ec,
0x06cbeee33576139d,
0xabf8b60be77d73,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0xe4bd44e5607cfd48,
0xc28f069fbb966e3d,
0x5e6dd9e7e0acccb0,
0x30644e72e131a029,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0x1264475e420ac20f,
0x2cfa95859526b0d4,
0x072fc0af59c61f30,
0x757cab3a41d3cdc,
]),
}
},
im: {
BN254 {
val: U256([
0xe85845e34c4a5b9c,
0xa20b7dfd71573c93,
0x18e9b79ba4e2606c,
0xca6b035381e35b6,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0x3c208c16d87cfd46,
0x97816a916871ca8d,
0xb85045b68181585d,
0x30644e72e131a029,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0x6615563bfbb318d7,
0x3b2f4c893f42a916,
0xcf96a5d90a9accfd,
0x1ddf9756b8cbf849,
]),
}
},
im: {
BN254 {
val: U256([
0x71c39bb757899a9b,
0x2307d819d98302a7,
0x121dc8b86f6c4ccf,
0x0bfab77f2c36b843,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0x5763473177fffffe,
0xd4f263f1acdb5c4f,
0x59e26bcea0d48bac,
0x0,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0x53b10eddb9a856c8,
0x0e34b703aa1bf842,
0xc866e529b0d4adcd,
0x1687cca314aebb6d,
]),
}
},
im: {
BN254 {
val: U256([
0xc58be1eae3bc3c46,
0x187dc4add09d90a0,
0xb18456d34c0b44c0,
0x2fb855bcd54a22b6,
]),
}
},
},
Fp2 {
re: {
BN254 {
val: U256([
0x5763473177ffffff,
0xd4f263f1acdb5c4f,
0x59e26bcea0d48bac,
0x0,
]),
}
},
im: { BN254 { val: U256::zero() } },
},
Fp2 {
re: {
BN254 {
val: U256([
0x29bc44b896723b38,
0x6a86d50bd34b19b9,
0xb120850727bb392d,
0x290c83bf3d14634d,
]),
}
},
im: {
BN254 {
val: U256([
0x53c846338c32a1ab,
0xf575ec93f71a8df9,
0x9f668e1adc9ef7f0,
0x23bd9e3da9136a73,
]),
}
},
},
];
}
impl Adj for Fp2<BLS381> {
fn mul_adj(self) -> Self {
Fp2 {
re: self.re - self.im,
im: self.re + self.im,
}
}
const FROB_T: [[Fp2<BLS381>; 6]; 2] = [[Fp2::<BLS381>::ZERO; 6]; 2];
const FROB_Z: [Fp2<BLS381>; 12] = [Fp2::<BLS381>::ZERO; 12];
}
/// The degree 3 field extension Fp6 over Fp2 is given by adjoining t, where t^3 = 1 + i
/// Fp6 has basis 1, t, t^2 over Fp2
#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) struct Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
pub t0: Fp2<T>,
pub t1: Fp2<T>,
pub t2: Fp2<T>,
}
impl<T> Distribution<Fp6<T>> for Standard
where
T: FieldExt,
Fp2<T>: Adj,
Standard: Distribution<T>,
{
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Fp6<T> {
let (t0, t1, t2) = rng.gen::<(Fp2<T>, Fp2<T>, Fp2<T>)>();
Fp6 { t0, t1, t2 }
}
}
impl<T> Add for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn add(self, other: Self) -> Self {
Fp6 {
t0: self.t0 + other.t0,
t1: self.t1 + other.t1,
t2: self.t2 + other.t2,
}
}
}
impl<T> Neg for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn neg(self) -> Self::Output {
Fp6 {
t0: -self.t0,
t1: -self.t1,
t2: -self.t2,
}
}
}
impl<T> Sub for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn sub(self, other: Self) -> Self {
Fp6 {
t0: self.t0 - other.t0,
t1: self.t1 - other.t1,
t2: self.t2 - other.t2,
}
}
}
impl<T> Mul for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn mul(self, other: Self) -> Self {
Fp6 {
t0: self.t0 * other.t0 + (self.t1 * other.t2 + self.t2 * other.t1).mul_adj(),
t1: self.t0 * other.t1 + self.t1 * other.t0 + (self.t2 * other.t2).mul_adj(),
t2: self.t0 * other.t2 + self.t1 * other.t1 + self.t2 * other.t0,
}
}
}
/// This function scalar multiplies an Fp6 by an Fp2
impl<T> Mul<Fp2<T>> for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Fp6<T>;
fn mul(self, other: Fp2<T>) -> Self {
Fp6 {
t0: other * self.t0,
t1: other * self.t1,
t2: other * self.t2,
}
}
}
impl<T> Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
/// This function multiplies an Fp6 element by t, and hence shifts the bases,
/// where the t^2 coefficient picks up a factor of 1+i as the 1 coefficient of the output
fn sh(self) -> Fp6<T> {
Fp6 {
t0: self.t2.mul_adj(),
t1: self.t0,
t2: self.t1,
}
}
}
impl<T> Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
/// The nth frobenius endomorphism of a p^q field is given by mapping
/// x to x^(p^n)
/// which sends a + bt + ct^2: Fp6 to
/// a^(p^n) + b^(p^n) * t^(p^n) + c^(p^n) * t^(2p^n)
/// The Fp2 coefficients are determined by the comment in the conj method,
/// while the values of
/// t^(p^n) and t^(2p^n)
/// are precomputed in the constant arrays FROB_T1 and FROB_T2
pub(crate) fn frob(self, n: usize) -> Fp6<T> {
let n = n % 6;
let frob_t1 = Fp2::<T>::FROB_T[0][n];
let frob_t2 = Fp2::<T>::FROB_T[1][n];
if n % 2 != 0 {
Fp6 {
t0: self.t0.conj(),
t1: frob_t1 * self.t1.conj(),
t2: frob_t2 * self.t2.conj(),
}
} else {
Fp6 {
t0: self.t0,
t1: frob_t1 * self.t1,
t2: frob_t2 * self.t2,
}
}
}
}
impl<T> FieldExt for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
const ZERO: Fp6<T> = Fp6 {
t0: Fp2::<T>::ZERO,
t1: Fp2::<T>::ZERO,
t2: Fp2::<T>::ZERO,
};
const UNIT: Fp6<T> = Fp6 {
t0: Fp2::<T>::UNIT,
t1: Fp2::<T>::ZERO,
t2: Fp2::<T>::ZERO,
};
fn new(val: usize) -> Fp6<T> {
Fp6 {
t0: Fp2::<T>::new(val),
t1: Fp2::<T>::ZERO,
t2: Fp2::<T>::ZERO,
}
}
/// Let x_n = x^(p^n) and note that
/// x_0 = x^(p^0) = x^1 = x
/// (x_n)_m = (x^(p^n))^(p^m) = x^(p^n * p^m) = x^(p^(n+m)) = x_{n+m}
/// By Galois Theory, given x: Fp6, the product
/// phi = x_0 * x_1 * x_2 * x_3 * x_4 * x_5
/// lands in BN254, and hence the inverse of x is given by
/// (x_1 * x_2 * x_3 * x_4 * x_5) / phi
/// We can save compute by rearranging the numerator:
/// (x_1 * x_3) * x_5 * (x_1 * x_3)_1
/// By Galois theory, the following are in Fp2 and are complex conjugates
/// x_1 * x_3 * x_5, x_0 * x_2 * x_4
/// and therefore
/// phi = ||x_1 * x_3 * x_5||^2
/// and hence the inverse is given by
/// ([x_1 * x_3] * x_5) * [x_1 * x_3]_1 / ||[x_1 * x_3] * x_5||^2
fn inv(self) -> Fp6<T> {
let prod_13 = self.frob(1) * self.frob(3);
let prod_135 = (prod_13 * self.frob(5)).t0;
let phi = prod_135.norm_sq();
let prod_odds_over_phi = prod_135 * phi.inv();
let prod_24 = prod_13.frob(1);
prod_24 * prod_odds_over_phi
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl<T> Div for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inv()
}
}
/// The degree 2 field extension Fp12 over Fp6 is given by
/// adjoining z, where z^2 = t. It thus has basis 1, z over Fp6
#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) struct Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
pub z0: Fp6<T>,
pub z1: Fp6<T>,
}
impl<T> FieldExt for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
const ZERO: Fp12<T> = Fp12 {
z0: Fp6::<T>::ZERO,
z1: Fp6::<T>::ZERO,
};
const UNIT: Fp12<T> = Fp12 {
z0: Fp6::<T>::UNIT,
z1: Fp6::<T>::ZERO,
};
fn new(val: usize) -> Fp12<T> {
Fp12 {
z0: Fp6::<T>::new(val),
z1: Fp6::<T>::ZERO,
}
}
/// By Galois Theory, given x: Fp12, the product
/// phi = Prod_{i=0}^11 x_i
/// lands in BN254, and hence the inverse of x is given by
/// (Prod_{i=1}^11 x_i) / phi
/// The 6th Frob map is nontrivial but leaves Fp6 fixed and hence must be the conjugate:
/// x_6 = (a + bz)_6 = a - bz = x.conj()
/// Letting prod_17 = x_1 * x_7, the remaining factors in the numerator can be expressed as:
/// [(prod_17) * (prod_17)_2] * (prod_17)_4 * [(prod_17) * (prod_17)_2]_1
/// By Galois theory, both the following are in Fp2 and are complex conjugates
/// prod_odds, prod_evens
/// Thus phi = ||prod_odds||^2, and hence the inverse is given by
/// prod_odds * prod_evens_except_six * x.conj() / ||prod_odds||^2
fn inv(self) -> Fp12<T> {
let prod_17 = (self.frob(1) * self.frob(7)).z0;
let prod_1379 = prod_17 * prod_17.frob(2);
let prod_odds = (prod_1379 * prod_17.frob(4)).t0;
let phi = prod_odds.norm_sq();
let prod_odds_over_phi = prod_odds * phi.inv();
let prod_evens_except_six = prod_1379.frob(1);
let prod_except_six = prod_evens_except_six * prod_odds_over_phi;
self.conj() * prod_except_six
}
}
impl<T> Distribution<Fp12<T>> for Standard
where
T: FieldExt,
Fp2<T>: Adj,
Standard: Distribution<T>,
{
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Fp12<T> {
let (z0, z1) = rng.gen::<(Fp6<T>, Fp6<T>)>();
Fp12 { z0, z1 }
}
}
impl<T> Add for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn add(self, other: Self) -> Self {
Fp12 {
z0: self.z0 + other.z0,
z1: self.z1 + other.z1,
}
}
}
impl<T> Neg for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn neg(self) -> Self::Output {
Fp12 {
z0: -self.z0,
z1: -self.z1,
}
}
}
impl<T> Sub for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn sub(self, other: Self) -> Self {
Fp12 {
z0: self.z0 - other.z0,
z1: self.z1 - other.z1,
}
}
}
impl<T> Mul for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn mul(self, other: Self) -> Self {
let h0 = self.z0 * other.z0;
let h1 = self.z1 * other.z1;
let h01 = (self.z0 + self.z1) * (other.z0 + other.z1);
Fp12 {
z0: h0 + h1.sh(),
z1: h01 - (h0 + h1),
}
}
}
/// This function scalar multiplies an Fp12 by an Fp6
impl<T> Mul<Fp6<T>> for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Fp12<T>;
fn mul(self, other: Fp6<T>) -> Self {
Fp12 {
z0: other * self.z0,
z1: other * self.z1,
}
}
}
impl<T> Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
fn conj(self) -> Fp12<T> {
Fp12 {
z0: self.z0,
z1: -self.z1,
}
}
}
impl<T> Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
/// The nth frobenius endomorphism of a p^q field is given by mapping
/// x to x^(p^n)
/// which sends a + bz: Fp12 to
/// a^(p^n) + b^(p^n) * z^(p^n)
/// where the values of z^(p^n) are precomputed in the constant array FROB_Z
pub(crate) fn frob(self, n: usize) -> Fp12<T> {
let n = n % 12;
Fp12 {
z0: self.z0.frob(n),
z1: self.z1.frob(n) * (Fp2::<T>::FROB_Z[n]),
}
}
}
#[allow(clippy::suspicious_arithmetic_impl)]
impl<T> Div for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
{
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inv()
}
}
pub trait Stack {
const SIZE: usize;
fn to_stack(&self) -> Vec<U256>;
fn from_stack(stack: &[U256]) -> Self;
}
impl Stack for BN254 {
const SIZE: usize = 1;
fn to_stack(&self) -> Vec<U256> {
vec![self.val]
}
fn from_stack(stack: &[U256]) -> BN254 {
BN254 { val: stack[0] }
}
}
impl Stack for BLS381 {
const SIZE: usize = 2;
fn to_stack(&self) -> Vec<U256> {
vec![self.lo(), self.hi()]
}
fn from_stack(stack: &[U256]) -> BLS381 {
let mut val = [0u64; 8];
val[..4].copy_from_slice(&stack[0].0);
val[4..].copy_from_slice(&stack[1].0);
BLS381 { val: U512(val) }
}
}
impl<T: FieldExt + Stack> Stack for Fp2<T> {
const SIZE: usize = 2 * T::SIZE;
fn to_stack(&self) -> Vec<U256> {
let mut stack = self.re.to_stack();
stack.extend(self.im.to_stack());
stack
}
fn from_stack(stack: &[U256]) -> Fp2<T> {
let field_size = T::SIZE;
let re = T::from_stack(&stack[0..field_size]);
let im = T::from_stack(&stack[field_size..2 * field_size]);
Fp2 { re, im }
}
}
impl<T> Stack for Fp6<T>
where
T: FieldExt,
Fp2<T>: Adj,
Fp2<T>: Stack,
{
const SIZE: usize = 3 * Fp2::<T>::SIZE;
fn to_stack(&self) -> Vec<U256> {
let mut stack = self.t0.to_stack();
stack.extend(self.t1.to_stack());
stack.extend(self.t2.to_stack());
stack
}
fn from_stack(stack: &[U256]) -> Self {
let field_size = Fp2::<T>::SIZE;
let t0 = Fp2::<T>::from_stack(&stack[0..field_size]);
let t1 = Fp2::<T>::from_stack(&stack[field_size..2 * field_size]);
let t2 = Fp2::<T>::from_stack(&stack[2 * field_size..3 * field_size]);
Fp6 { t0, t1, t2 }
}
}
impl<T> Stack for Fp12<T>
where
T: FieldExt,
Fp2<T>: Adj,
Fp6<T>: Stack,
{
const SIZE: usize = 2 * Fp6::<T>::SIZE;
fn to_stack(&self) -> Vec<U256> {
let mut stack = self.z0.to_stack();
stack.extend(self.z1.to_stack());
stack
}
fn from_stack(stack: &[U256]) -> Self {
let field_size = Fp6::<T>::SIZE;
let z0 = Fp6::<T>::from_stack(&stack[0..field_size]);
let z1 = Fp6::<T>::from_stack(&stack[field_size..2 * field_size]);
Fp12 { z0, z1 }
}
}