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Pass modulus to prime_field_constants_and_sqrt by reference

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This commit is contained in:
Jack Grigg 2019-12-18 17:53:39 -06:00
parent f5914fe804
commit 26ef9c9842
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GPG Key ID: 9E8255172BBF9898
1 changed files with 12 additions and 14 deletions
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26
ff/ff_derive/src/lib.rs
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@ -47,7 +47,7 @@ pub fn prime_field(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let mut gen = proc_macro2::TokenStream::new(); let mut gen = proc_macro2::TokenStream::new();
let (constants_impl, sqrt_impl) = let (constants_impl, sqrt_impl) =
prime_field_constants_and_sqrt(&ast.ident, &repr_ident, modulus, limbs, generator); prime_field_constants_and_sqrt(&ast.ident, &repr_ident, &modulus, limbs, generator);
gen.extend(constants_impl); gen.extend(constants_impl);
gen.extend(prime_field_repr_impl(&repr_ident, limbs)); gen.extend(prime_field_repr_impl(&repr_ident, limbs));
@ -383,7 +383,7 @@ fn test_exp() {
fn prime_field_constants_and_sqrt( fn prime_field_constants_and_sqrt(
name: &syn::Ident, name: &syn::Ident,
repr: &syn::Ident, repr: &syn::Ident,
modulus: BigUint, modulus: &BigUint,
limbs: usize, limbs: usize,
generator: BigUint, generator: BigUint,
) -> (proc_macro2::TokenStream, proc_macro2::TokenStream) { ) -> (proc_macro2::TokenStream, proc_macro2::TokenStream) {
@ -396,28 +396,26 @@ fn prime_field_constants_and_sqrt(
let repr_shave_bits = (64 * limbs as u32) - biguint_num_bits(modulus.clone()); let repr_shave_bits = (64 * limbs as u32) - biguint_num_bits(modulus.clone());
// Compute R = 2**(64 * limbs) mod m // Compute R = 2**(64 * limbs) mod m
let r = (BigUint::one() << (limbs * 64)) % &modulus; let r = (BigUint::one() << (limbs * 64)) % modulus;
// modulus - 1 = 2^s * t // modulus - 1 = 2^s * t
let mut s: u32 = 0; let mut s: u32 = 0;
let mut t = &modulus - BigUint::from_str("1").unwrap(); let mut t = modulus - BigUint::from_str("1").unwrap();
while t.is_even() { while t.is_even() {
t = t >> 1; t = t >> 1;
s += 1; s += 1;
} }
// Compute 2^s root of unity given the generator // Compute 2^s root of unity given the generator
let root_of_unity = biguint_to_u64_vec( let root_of_unity =
(exp(generator.clone(), &t, &modulus) * &r) % &modulus, biguint_to_u64_vec((exp(generator.clone(), &t, &modulus) * &r) % modulus, limbs);
limbs, let generator = biguint_to_u64_vec((generator.clone() * &r) % modulus, limbs);
);
let generator = biguint_to_u64_vec((generator.clone() * &r) % &modulus, limbs);
let sqrt_impl = if (&modulus % BigUint::from_str("4").unwrap()) let sqrt_impl = if (modulus % BigUint::from_str("4").unwrap())
== BigUint::from_str("3").unwrap() == BigUint::from_str("3").unwrap()
{ {
let mod_plus_1_over_4 = let mod_plus_1_over_4 =
biguint_to_u64_vec((&modulus + BigUint::from_str("1").unwrap()) >> 2, limbs); biguint_to_u64_vec((modulus + BigUint::from_str("1").unwrap()) >> 2, limbs);
quote! { quote! {
impl ::ff::SqrtField for #name { impl ::ff::SqrtField for #name {
@ -436,7 +434,7 @@ fn prime_field_constants_and_sqrt(
} }
} }
} }
} else if (&modulus % BigUint::from_str("16").unwrap()) == BigUint::from_str("1").unwrap() { } else if (modulus % BigUint::from_str("16").unwrap()) == BigUint::from_str("1").unwrap() {
let t_minus_1_over_2 = biguint_to_u64_vec((&t - BigUint::one()) >> 1, limbs); let t_minus_1_over_2 = biguint_to_u64_vec((&t - BigUint::one()) >> 1, limbs);
quote! { quote! {
@ -490,10 +488,10 @@ fn prime_field_constants_and_sqrt(
}; };
// Compute R^2 mod m // Compute R^2 mod m
let r2 = biguint_to_u64_vec((&r * &r) % &modulus, limbs); let r2 = biguint_to_u64_vec((&r * &r) % modulus, limbs);
let r = biguint_to_u64_vec(r, limbs); let r = biguint_to_u64_vec(r, limbs);
let modulus = biguint_to_real_u64_vec(modulus, limbs); let modulus = biguint_to_real_u64_vec(modulus.clone(), limbs);
// Compute -m^-1 mod 2**64 by exponentiating by totient(2**64) - 1 // Compute -m^-1 mod 2**64 by exponentiating by totient(2**64) - 1
let mut inv = 1u64; let mut inv = 1u64;