73 lines
2.2 KiB
Rust
73 lines
2.2 KiB
Rust
use crate::private_key::PrivateKeyBytes;
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use digest::Digest;
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use ripemd::Ripemd160;
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use sha2::Sha256;
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use thiserror::Error;
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pub type PublicKeyBytes = [u8; 33];
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pub trait PublicKey: Sized {
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type Err: std::error::Error;
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fn from_bytes(b: &PublicKeyBytes) -> Self;
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fn to_bytes(&self) -> PublicKeyBytes;
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/// Derive a child [`PublicKey`] with given `PrivateKeyBytes`.
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///
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/// # Errors
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///
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/// An error may be returned if:
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/// * A nonzero `other` is provided.
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/// * An error specific to the given algorithm was encountered.
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fn derive_child(&self, other: PrivateKeyBytes) -> Result<Self, Self::Err>;
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fn fingerprint(&self) -> [u8; 4] {
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let hash = Sha256::new().chain_update(self.to_bytes()).finalize();
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let hash = Ripemd160::new().chain_update(hash).finalize();
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// Note: Safety assured by type returned from Ripemd160
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hash[..4].try_into().unwrap()
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}
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}
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#[derive(Clone, Debug, Error)]
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pub enum PublicKeyError {
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#[error("The provided public key must be nonzero, but is not")]
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NonZero,
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#[error("Unable to convert point to key")]
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PointToKey(#[from] k256::elliptic_curve::Error),
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}
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#[cfg(feature = "secp256k1")]
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use k256::{
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elliptic_curve::{group::prime::PrimeCurveAffine, sec1::ToEncodedPoint},
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AffinePoint, NonZeroScalar,
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};
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#[cfg(feature = "secp256k1")]
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impl PublicKey for k256::PublicKey {
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type Err = PublicKeyError;
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fn from_bytes(b: &PublicKeyBytes) -> Self {
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Self::from_sec1_bytes(b).expect("Invalid public key bytes")
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}
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fn to_bytes(&self) -> PublicKeyBytes {
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// Note: Safety assured by type returned from EncodedPoint
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self.to_encoded_point(true).as_bytes().try_into().unwrap()
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}
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fn derive_child(&self, other: PrivateKeyBytes) -> Result<Self, Self::Err> {
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if other.iter().all(|n| n == &0) {
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return Err(PublicKeyError::NonZero);
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}
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// Checked: See above
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let scalar = Option::<NonZeroScalar>::from(NonZeroScalar::from_repr(other.into()))
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.expect("Should have been able to get a NonZeroScalar");
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let point = self.to_projective() + (AffinePoint::generator() * *scalar);
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Self::from_affine(point.into()).map_err(From::from)
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}
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}
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