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refactor(fiat-crypto): Inversion #66

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refactor(fiat-crypto): Inversion #66

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f4ce1f4
implement inversion arithmetic for base field (fp, u64)
TalDerei Dec 28, 2023
10f1d56
implement inversion arithmetic for scalar field (fq, u64)
TalDerei Dec 28, 2023
3ac35a1
implement inversion arithmetic for decaf377 scalar field (fr, u64)
TalDerei Dec 28, 2023
1815570
implement inversion arithmetic for base field (fp, u32)
TalDerei Dec 28, 2023
6ceb70e
implement inversion arithmetic for scalar field (fq, u32)
TalDerei Dec 28, 2023
cccb3ca
implement inversion arithmetic for decaf377 scalar field (fr, u32)
TalDerei Dec 28, 2023
b134d92
fmt
TalDerei Dec 28, 2023
12d8532
added zero checks
TalDerei Dec 28, 2023
bddf3c9
revert changes to generated fiat-crypto + fix tests
TalDerei Jan 1, 2024
85e5b46
added global constants
Jan 11, 2024
8b7b117
proptest for inversion
Jan 11, 2024
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126 changes: 116 additions & 10 deletions src/fields/u32/fp/wrapper.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
use super::fiat;
use core::ops::{Add, Mul, Neg, Sub};

use super::fiat;
const NUM_LIMBS: usize = 12;
const PRIME_ORDER: usize = 377;

#[derive(Copy, Clone)]
pub struct Fp(fiat::FpMontgomeryDomainFieldElement);
Expand All @@ -24,8 +26,8 @@ impl Eq for Fp {}

impl Fp {
pub fn from_bytes(bytes: &[u8; 48]) -> Self {
let mut x_non_montgomery = fiat::FpNonMontgomeryDomainFieldElement([0; 12]);
let mut x = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut x_non_montgomery = fiat::FpNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
let mut x = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);

fiat::fp_from_bytes(&mut x_non_montgomery.0, &bytes);
fiat::fp_to_montgomery(&mut x, &x_non_montgomery);
Expand All @@ -34,7 +36,7 @@ impl Fp {
}

pub fn to_bytes(&self) -> [u8; 48] {
let mut x_non_montgomery = fiat::FpNonMontgomeryDomainFieldElement([0; 12]);
let mut x_non_montgomery = fiat::FpNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
let mut bytes = [0u8; 48];

fiat::fp_from_montgomery(&mut x_non_montgomery, &self.0);
Expand All @@ -44,7 +46,7 @@ impl Fp {
}

pub fn zero() -> Self {
Self(fiat::FpMontgomeryDomainFieldElement([0; 12]))
Self(fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]))
}

pub fn one() -> Self {
Expand All @@ -54,17 +56,96 @@ impl Fp {
}

pub fn square(&self) -> Self {
let mut result = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_square(&mut result, &self.0);
Self(result)
}

fn inverse(&self) -> Option<Fp> {
if self == &Fp::zero() {
return None;
}

const LEN_PRIME: usize = PRIME_ORDER;
const ITERATIONS: usize = (49 * LEN_PRIME + 57) / 17;

let mut a = fiat::FpNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_from_montgomery(&mut a, &self.0);
let mut d = 1;
let mut f: [u32; NUM_LIMBS + 1] = [0u32; NUM_LIMBS + 1];
fiat::fp_msat(&mut f);
let mut g: [u32; NUM_LIMBS + 1] = [0u32; NUM_LIMBS + 1];
let mut v: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
let mut r: [u32; NUM_LIMBS] = Fp::one().0 .0;
let mut i = 0;
let mut j = 0;

while j < NUM_LIMBS {
g[j] = a[j];
j += 1;
}

let mut out1: u32 = 0;
let mut out2: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out3: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out4: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out5: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out6: u32 = 0;
let mut out7: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out8: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out9: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out10: [u32; NUM_LIMBS] = [0; NUM_LIMBS];

while i < ITERATIONS - ITERATIONS % 2 {
fiat::fp_divstep(
&mut out1, &mut out2, &mut out3, &mut out4, &mut out5, d, &f, &g, &v, &r,
);
fiat::fp_divstep(
&mut out6, &mut out7, &mut out8, &mut out9, &mut out10, out1, &out2, &out3, &out4,
&out5,
);
d = out6;
f = out7;
g = out8;
v = out9;
r = out10;
i += 2;
}

if ITERATIONS % 2 != 0 {
fiat::fp_divstep(
&mut out1, &mut out2, &mut out3, &mut out4, &mut out5, d, &f, &g, &v, &r,
);
v = out4;
f = out2;
}

let s = ((f[f.len() - 1] >> 32 - 1) & 1) as u8;
let mut neg = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_opp(&mut neg, &fiat::FpMontgomeryDomainFieldElement(v));

let mut v_prime: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
fiat::fp_selectznz(&mut v_prime, s, &v, &neg.0);

let mut pre_comp: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
fiat::fp_divstep_precomp(&mut pre_comp);

let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_mul(
&mut result,
&fiat::FpMontgomeryDomainFieldElement(v_prime),
&fiat::FpMontgomeryDomainFieldElement(pre_comp),
);

Some(Fp(result))
}
}

impl Add<Fp> for Fp {
type Output = Fp;

fn add(self, other: Fp) -> Fp {
let mut result = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_add(&mut result, &self.0, &other.0);
Fp(result)
}
Expand All @@ -74,7 +155,7 @@ impl Sub<Fp> for Fp {
type Output = Fp;

fn sub(self, other: Fp) -> Fp {
let mut result = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_sub(&mut result, &self.0, &other.0);
Fp(result)
}
Expand All @@ -84,7 +165,7 @@ impl Mul<Fp> for Fp {
type Output = Fp;

fn mul(self, other: Fp) -> Fp {
let mut result = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_mul(&mut result, &self.0, &other.0);
Fp(result)
}
Expand All @@ -94,8 +175,33 @@ impl Neg for Fp {
type Output = Fp;

fn neg(self) -> Fp {
let mut result = fiat::FpMontgomeryDomainFieldElement([0; 12]);
let mut result = fiat::FpMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fp_opp(&mut result, &self.0);
Fp(result)
}
}

#[cfg(test)]
mod tests {
use proptest::prelude::*;
use proptest::{
arbitrary::any,
strategy::{BoxedStrategy, Strategy},
};

use super::*;

fn fp_strategy() -> BoxedStrategy<Fp> {
any::<[u8; 48]>()
.prop_map(|bytes| Fp::from_bytes(&bytes))
.boxed()
}

proptest! {
#[test]
fn inversion_proptest(element in fp_strategy().prop_filter("Non-zero element", |e| e != &Fp::zero())) {
let inverse = element.inverse().unwrap();
assert_eq!(element.mul(inverse), Fp::one());
}
}
}
124 changes: 115 additions & 9 deletions src/fields/u32/fq/wrapper.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
use super::fiat;
use core::ops::{Add, Mul, Neg, Sub};

use super::fiat;
const NUM_LIMBS: usize = 8;
const PRIME_ORDER: usize = 253;

#[derive(Copy, Clone)]
pub struct Fq(fiat::FqMontgomeryDomainFieldElement);
Expand All @@ -24,8 +26,8 @@ impl Eq for Fq {}

impl Fq {
pub fn from_bytes(bytes: &[u8; 32]) -> Self {
let mut x_non_montgomery = fiat::FqNonMontgomeryDomainFieldElement([0; 8]);
let mut x = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut x_non_montgomery = fiat::FqNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
let mut x = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);

fiat::fq_from_bytes(&mut x_non_montgomery.0, &bytes);
fiat::fq_to_montgomery(&mut x, &x_non_montgomery);
Expand All @@ -34,7 +36,7 @@ impl Fq {
}

pub fn to_bytes(&self) -> [u8; 32] {
let mut x_non_montgomery = fiat::FqNonMontgomeryDomainFieldElement([0; 8]);
let mut x_non_montgomery = fiat::FqNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
let mut bytes = [0u8; 32];

fiat::fq_from_montgomery(&mut x_non_montgomery, &self.0);
Expand All @@ -54,17 +56,96 @@ impl Fq {
}

pub fn square(&self) -> Self {
let mut result = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_square(&mut result, &self.0);
Self(result)
}

fn inverse(&self) -> Option<Fq> {
if self == &Fq::zero() {
return None;
}

const LEN_PRIME: usize = PRIME_ORDER;
const ITERATIONS: usize = (49 * LEN_PRIME + 57) / 17;

let mut a = fiat::FqNonMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_from_montgomery(&mut a, &self.0);
let mut d = 1;
let mut f: [u32; 9] = [0u32; NUM_LIMBS + 1];
fiat::fq_msat(&mut f);
let mut g: [u32; NUM_LIMBS + 1] = [0u32; NUM_LIMBS + 1];
let mut v: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
let mut r: [u32; NUM_LIMBS] = Fq::one().0 .0;
let mut i = 0;
let mut j = 0;

while j < NUM_LIMBS {
g[j] = a[j];
j += 1;
}

let mut out1: u32 = 0;
let mut out2: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out3: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out4: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out5: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out6: u32 = 0;
let mut out7: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out8: [u32; NUM_LIMBS + 1] = [0; NUM_LIMBS + 1];
let mut out9: [u32; NUM_LIMBS] = [0; NUM_LIMBS];
let mut out10: [u32; NUM_LIMBS] = [0; NUM_LIMBS];

while i < ITERATIONS - ITERATIONS % 2 {
fiat::fq_divstep(
&mut out1, &mut out2, &mut out3, &mut out4, &mut out5, d, &f, &g, &v, &r,
);
fiat::fq_divstep(
&mut out6, &mut out7, &mut out8, &mut out9, &mut out10, out1, &out2, &out3, &out4,
&out5,
);
d = out6;
f = out7;
g = out8;
v = out9;
r = out10;
i += 2;
}

if ITERATIONS % 2 != 0 {
fiat::fq_divstep(
&mut out1, &mut out2, &mut out3, &mut out4, &mut out5, d, &f, &g, &v, &r,
);
v = out4;
f = out2;
}

let s = ((f[f.len() - 1] >> 32 - 1) & 1) as u8;
let mut neg = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_opp(&mut neg, &fiat::FqMontgomeryDomainFieldElement(v));

let mut v_prime: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
fiat::fq_selectznz(&mut v_prime, s, &v, &neg.0);

let mut pre_comp: [u32; NUM_LIMBS] = [0u32; NUM_LIMBS];
fiat::fq_divstep_precomp(&mut pre_comp);

let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_mul(
&mut result,
&fiat::FqMontgomeryDomainFieldElement(v_prime),
&fiat::FqMontgomeryDomainFieldElement(pre_comp),
);

Some(Fq(result))
}
}

impl Add<Fq> for Fq {
type Output = Fq;

fn add(self, other: Fq) -> Fq {
let mut result = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_add(&mut result, &self.0, &other.0);
Fq(result)
}
Expand All @@ -74,7 +155,7 @@ impl Sub<Fq> for Fq {
type Output = Fq;

fn sub(self, other: Fq) -> Fq {
let mut result = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_sub(&mut result, &self.0, &other.0);
Fq(result)
}
Expand All @@ -84,7 +165,7 @@ impl Mul<Fq> for Fq {
type Output = Fq;

fn mul(self, other: Fq) -> Fq {
let mut result = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_mul(&mut result, &self.0, &other.0);
Fq(result)
}
Expand All @@ -94,8 +175,33 @@ impl Neg for Fq {
type Output = Fq;

fn neg(self) -> Fq {
let mut result = fiat::FqMontgomeryDomainFieldElement([0; 8]);
let mut result = fiat::FqMontgomeryDomainFieldElement([0; NUM_LIMBS]);
fiat::fq_opp(&mut result, &self.0);
Fq(result)
}
}

#[cfg(test)]
mod tests {
use proptest::prelude::*;
use proptest::{
arbitrary::any,
strategy::{BoxedStrategy, Strategy},
};

use super::*;

fn fp_strategy() -> BoxedStrategy<Fq> {
any::<[u8; 32]>()
.prop_map(|bytes| Fq::from_bytes(&bytes))
.boxed()
}

proptest! {
#[test]
fn inversion_proptest(element in fp_strategy().prop_filter("Non-zero element", |e| e != &Fq::zero())) {
let inverse = element.inverse().unwrap();
assert_eq!(element.mul(inverse), Fq::one());
}
}
}
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