74 lines
2.0 KiB
Rust
74 lines
2.0 KiB
Rust
//! Schnorr signature signing keys
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use rand_core::{CryptoRng, RngCore};
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use crate::{Ciphersuite, Error, Field, Group, Signature, VerifyingKey};
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/// A signing key for a Schnorr signature on a FROST [`Ciphersuite::Group`].
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#[derive(Copy, Clone)]
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pub struct SigningKey<C>
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where
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C: Ciphersuite,
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{
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scalar: <<C::Group as Group>::Field as Field>::Scalar,
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}
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impl<C> SigningKey<C>
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where
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C: Ciphersuite,
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{
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/// Generate a new signing key.
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pub fn new<R: RngCore + CryptoRng>(mut rng: R) -> SigningKey<C> {
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let scalar = <<C::Group as Group>::Field as Field>::random_nonzero(&mut rng);
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SigningKey { scalar }
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}
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/// Deserialize from bytes
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pub fn from_bytes(
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bytes: <<C::Group as Group>::Field as Field>::Serialization,
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) -> Result<SigningKey<C>, Error> {
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<<C::Group as Group>::Field as Field>::deserialize(&bytes)
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.map(|scalar| SigningKey { scalar })
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}
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/// Serialize `SigningKey` to bytes
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pub fn to_bytes(&self) -> <<C::Group as Group>::Field as Field>::Serialization {
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<<C::Group as Group>::Field as Field>::serialize(&self.scalar)
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}
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/// Create a signature `msg` using this `SigningKey`.
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pub fn sign<R: RngCore + CryptoRng>(&self, mut rng: R, msg: &[u8]) -> Signature<C> {
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let k = <<C::Group as Group>::Field as Field>::random_nonzero(&mut rng);
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let R = <C::Group as Group>::generator() * k;
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// Generate Schnorr challenge
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let c = crate::challenge::<C>(&R, &VerifyingKey::<C>::from(*self).element, msg);
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let z = k + (c.0 * self.scalar);
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Signature { R, z }
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}
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}
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impl<C> From<&SigningKey<C>> for VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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fn from(signing_key: &SigningKey<C>) -> Self {
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VerifyingKey {
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element: C::Group::generator() * signing_key.scalar,
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}
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}
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}
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impl<C> From<SigningKey<C>> for VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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fn from(signing_key: SigningKey<C>) -> Self {
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VerifyingKey::<C>::from(&signing_key)
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}
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}
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