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monero: match monero's stricter check when decompressing points (#515)

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* monero: match monero's stricter check when decompressing points

* Reverted type change for output key
This commit is contained in:
Justin Berman
2024-02-17 20:16:16 -08:00
committed by GitHub
parent 62a619a312
commit df85c09435
17 changed files with 727 additions and 58 deletions
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13
coins/monero/generators/src/hash_to_point.rs
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@@ -7,7 +7,16 @@ use dalek_ff_group::FieldElement;
use crate::hash;
/// Monero's hash to point function, as named `ge_fromfe_frombytes_vartime`.
/// Decompress canonically encoded ed25519 point
/// It does not check if the point is in the prime order subgroup
pub fn decompress_point(bytes: [u8; 32]) -> Option<EdwardsPoint> {
CompressedEdwardsY(bytes)
.decompress()
// Ban points which are either unreduced or -0
.filter(|point| point.compress().to_bytes() == bytes)
}
/// Monero's hash to point function, as named `hash_to_ec`.
pub fn hash_to_point(bytes: [u8; 32]) -> EdwardsPoint {
#[allow(non_snake_case)]
let A = FieldElement::from(486662u64);
@@ -47,5 +56,5 @@ pub fn hash_to_point(bytes: [u8; 32]) -> EdwardsPoint {
let mut bytes = Y.to_repr();
bytes[31] |= sign.unwrap_u8() << 7;
CompressedEdwardsY(bytes).decompress().unwrap().mul_by_cofactor()
decompress_point(bytes).unwrap().mul_by_cofactor()
}