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Fix 32-bit, no-std builds of crypto limbs

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This commit is contained in:
Luke Parker
2025-08-29 00:53:07 -04:00
parent ffe1b60a11
commit 0c71b6fc4d
5 changed files with 25 additions and 19 deletions
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13
crypto/prime-field/src/lib.rs
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@@ -11,6 +11,7 @@ pub use ff;
#[doc(hidden)]
pub mod __prime_field_private {
pub use paste;
#[cfg(feature = "std")]
pub use ff_group_tests;
use crypto_bigint::{Word, Uint, modular::ConstMontyParams};
@@ -38,15 +39,16 @@ pub mod __prime_field_private {
let mut i = 0;
while i < Uint::<LIMBS>::LIMBS {
let word: Word = value.as_limbs()[i].0;
let word = word as u64;
let bits = i * (Word::BITS as usize);
let j = bits / (u64::BITS as usize);
res[j] |= word << (bits % (u64::BITS as usize));
res[j] |= (word << (bits % (u64::BITS as usize))) as u64;
if (j + 1) < WORDS {
if let Some(remaining_bits) =
((bits % (u64::BITS as usize)) + (Word::BITS as usize)).checked_sub(u64::BITS as usize)
{
if remaining_bits != 0 {
res[j + 1] |= word >> ((Word::BITS as usize) - remaining_bits);
res[j + 1] |= (word >> ((Word::BITS as usize) - remaining_bits)) as u64;
}
}
}
@@ -126,7 +128,12 @@ macro_rules! odd_prime_field {
hex_str_without_prefix($multiplicative_generator_as_be_hex);
const MODULUS_BYTES: usize = MODULUS_WITHOUT_PREFIX.len() / 2;
type UnderlyingUint = Uint<{ MODULUS_BYTES.div_ceil(Limb::BYTES) }>;
/*
`crypto-bigint` only implements some methods for some limbs, due to the lack of const
generics. `next_power_of_two` pays a performance penalty yet effectively ensures this
`Uint` type is fully defined.
*/
type UnderlyingUint = Uint<{ MODULUS_BYTES.div_ceil(Limb::BYTES).next_power_of_two() }>;
const PADDED_MODULUS_WITHOUT_PREFIX_BYTES: [u8; 2 * UnderlyingUint::BYTES] = {
let mut res = [b'0'; 2 * UnderlyingUint::BYTES];