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Fix mutual_scalar_from_bytes

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It didn't properly grab bits, nor did it double as needed.
This commit is contained in:
Luke Parker
2022-07-05 08:10:16 -04:00
parent bfe34ea6f8
commit d17c9587b5
2 changed files with 22 additions and 18 deletions
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17
crypto/dleq/src/cross_group/mod.rs
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@@ -12,7 +12,7 @@ use group::{ff::{Field, PrimeField, PrimeFieldBits}, prime::PrimeGroup};
use crate::Generators;
pub mod scalar;
use scalar::scalar_convert;
use scalar::{scalar_convert, mutual_scalar_from_bytes};
pub(crate) mod schnorr;
use schnorr::SchnorrPoK;
@@ -121,22 +121,11 @@ impl<G0: PrimeGroup, G1: PrimeGroup> DLEqProof<G0, G1>
blinding_key
}
fn mutual_scalar_from_bytes(bytes: &[u8]) -> (G0::Scalar, G1::Scalar) {
let capacity = usize::try_from(G0::Scalar::CAPACITY.min(G1::Scalar::CAPACITY)).unwrap();
debug_assert!((bytes.len() * 8) >= capacity);
let mut accum = G0::Scalar::zero();
for b in 0 .. capacity {
accum += G0::Scalar::from((bytes[b / 8] & (1 << (b % 8))).into());
}
(accum, scalar_convert(accum).unwrap())
}
#[allow(non_snake_case)]
fn nonces<T: Transcript>(mut transcript: T, nonces: (G0, G1)) -> (G0::Scalar, G1::Scalar) {
transcript.append_message(b"nonce_0", nonces.0.to_bytes().as_ref());
transcript.append_message(b"nonce_1", nonces.1.to_bytes().as_ref());
Self::mutual_scalar_from_bytes(transcript.challenge(b"challenge").as_ref())
mutual_scalar_from_bytes(transcript.challenge(b"challenge").as_ref())
}
#[allow(non_snake_case)]
@@ -268,7 +257,7 @@ impl<G0: PrimeGroup, G1: PrimeGroup> DLEqProof<G0, G1>
rng,
transcript,
generators,
Self::mutual_scalar_from_bytes(digest.finalize().as_ref())
mutual_scalar_from_bytes(digest.finalize().as_ref())
)
}