94 lines
2.7 KiB
Rust
94 lines
2.7 KiB
Rust
use std::fmt::{self, Debug};
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use hex::FromHex;
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use crate::{Ciphersuite, Error, Group, Signature};
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/// A valid verifying key for Schnorr signatures over a FROST [`Ciphersuite::Group`].
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#[derive(Copy, Clone, PartialEq)]
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pub struct VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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pub(crate) element: <C::Group as Group>::Element,
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}
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impl<C> VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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// pub(crate) fn from(scalar: &<<C::Group as Group>::Field as Field>::Scalar) -> Self {
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// let element = <C::Group as Group>::generator() * *scalar;
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// VerifyingKey { element }
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// }
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/// Deserialize from bytes
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pub fn from_bytes(bytes: <C::Group as Group>::Serialization) -> Result<VerifyingKey<C>, Error> {
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<C::Group as Group>::deserialize(&bytes).map(|element| VerifyingKey { element })
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}
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/// Serialize `VerifyingKey` to bytes
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pub fn to_bytes(&self) -> <C::Group as Group>::Serialization {
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<C::Group as Group>::serialize(&self.element)
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}
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/// Verify a purported `signature` over `msg` made by this verification key.
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pub fn verify(&self, msg: &[u8], signature: &Signature<C>) -> Result<(), Error> {
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let c = crate::challenge::<C>(&signature.R, &self.element, msg);
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// Verify check is h * ( - z * B + R + c * A) == 0
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// h * ( z * B - c * A - R) == 0
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//
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// where h is the cofactor
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let zB = C::Group::generator() * signature.z;
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let cA = self.element * c.0;
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let check = (zB - cA - signature.R) * C::Group::cofactor();
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if check == C::Group::identity() {
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Ok(())
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} else {
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Err(Error::InvalidSignature)
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}
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}
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}
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impl<C> Debug for VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_tuple("VerifyingKey")
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.field(&hex::encode(self.to_bytes()))
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.finish()
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}
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}
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impl<C> FromHex for VerifyingKey<C>
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where
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C: Ciphersuite,
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{
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type Error = &'static str;
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fn from_hex<T: AsRef<[u8]>>(hex: T) -> Result<Self, Self::Error> {
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match FromHex::from_hex(hex) {
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Ok(bytes) => Self::from_bytes(bytes).map_err(|_| "malformed verifying key encoding"),
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Err(_) => Err("invalid hex"),
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}
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}
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}
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// impl<C: Ciphersuite> From<VerifyingKey<C>> for <C::Group as Group>::ElementSerialization {
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// fn from(pk: VerifyingKey<C>) -> <C::Group as Group>::ElementSerialization {
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// pk.bytes.bytes
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// }
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// }
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// impl<C: Ciphersuite> TryFrom<<C::Group as Group>::ElementSerialization> for VerifyingKey<C> {
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// type Error = Error;
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// fn try_from(bytes: [u8; 32]) -> Result<Self, Self::Error> {
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// VerifyingKeyBytes::from(bytes).try_into()
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// }
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// }
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