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ecdsa: impl Keypair for SigningKey #535

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Merged
tarcieri merged 1 commit into from
Sep 12, 2022
Merged

ecdsa: impl Keypair for SigningKey #535

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100 changes: 70 additions & 30 deletions ecdsa/src/sign.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,20 +22,23 @@ use signature::{
DigestSigner, RandomizedDigestSigner, RandomizedSigner, Signer,
};

#[cfg(feature = "verify")]
use {crate::verify::VerifyingKey, elliptic_curve::PublicKey};
#[cfg(feature = "pem")]
use {
crate::elliptic_curve::pkcs8::{EncodePrivateKey, SecretDocument},
core::str::FromStr,
};

#[cfg(feature = "pkcs8")]
use crate::elliptic_curve::{
pkcs8::{self, AssociatedOid, DecodePrivateKey},
sec1::{self, FromEncodedPoint, ToEncodedPoint},
AffinePoint,
};

#[cfg(feature = "pem")]
#[cfg(feature = "verify")]
use {
crate::elliptic_curve::pkcs8::{EncodePrivateKey, SecretDocument},
core::str::FromStr,
crate::{hazmat::VerifyPrimitive, verify::VerifyingKey},
elliptic_curve::{AffinePoint, PublicKey},
signature::Keypair,
};

/// ECDSA signing key. Generic over elliptic curves.
Expand All @@ -50,7 +53,12 @@ where
Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + Reduce<C::UInt> + SignPrimitive<C>,
SignatureSize<C>: ArrayLength<u8>,
{
inner: NonZeroScalar<C>,
/// ECDSA signing keys are non-zero elements of a given curve's scalar field.
secret_scalar: NonZeroScalar<C>,

/// Verifying key which corresponds to this signing key.
#[cfg(feature = "verify")]
verifying_key: VerifyingKey<C>,
}

impl<C> SigningKey<C>
Expand All @@ -61,23 +69,19 @@ where
{
/// Generate a cryptographically random [`SigningKey`].
pub fn random(rng: impl CryptoRng + RngCore) -> Self {
Self {
inner: NonZeroScalar::random(rng),
}
NonZeroScalar::<C>::random(rng).into()
}

/// Initialize signing key from a raw scalar serialized as a byte slice.
pub fn from_bytes(bytes: &[u8]) -> Result<Self> {
let inner = SecretKey::from_be_bytes(bytes)
.map(|sk| sk.to_nonzero_scalar())
.map_err(|_| Error::new())?;

Ok(Self { inner })
SecretKey::<C>::from_be_bytes(bytes)
.map(|sk| sk.to_nonzero_scalar().into())
.map_err(|_| Error::new())
}

/// Serialize this [`SigningKey`] as bytes
pub fn to_bytes(&self) -> FieldBytes<C> {
self.inner.to_repr()
self.secret_scalar.to_repr()
}

/// Borrow the secret [`NonZeroScalar`] value for this key.
Expand All @@ -88,16 +92,28 @@ where
///
/// Please treat it with the care it deserves!
pub fn as_nonzero_scalar(&self) -> &NonZeroScalar<C> {
&self.inner
&self.secret_scalar
}

/// Get the [`VerifyingKey`] which corresponds to this [`SigningKey`]
// TODO(tarcieri): make this return `&VerifyingKey<C>` in the next breaking release
#[cfg(feature = "verify")]
#[cfg_attr(docsrs, doc(cfg(feature = "verify")))]
pub fn verifying_key(&self) -> VerifyingKey<C> {
VerifyingKey {
inner: PublicKey::from_secret_scalar(&self.inner),
}
self.verifying_key
}
}

#[cfg(feature = "verify")]
#[cfg_attr(docsrs, doc(cfg(feature = "verify")))]
impl<C> AsRef<VerifyingKey<C>> for SigningKey<C>
where
C: PrimeCurve + ProjectiveArithmetic,
Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + Reduce<C::UInt> + SignPrimitive<C>,
SignatureSize<C>: ArrayLength<u8>,
{
fn as_ref(&self) -> &VerifyingKey<C> {
&self.verifying_key
}
}

Expand All @@ -108,7 +124,7 @@ where
SignatureSize<C>: ArrayLength<u8>,
{
fn ct_eq(&self, other: &Self) -> Choice {
self.inner.ct_eq(&other.inner)
self.secret_scalar.ct_eq(&other.secret_scalar)
}
}

Expand All @@ -130,7 +146,7 @@ where
SignatureSize<C>: ArrayLength<u8>,
{
fn drop(&mut self) {
self.inner.zeroize();
self.secret_scalar.zeroize();
}
}

Expand Down Expand Up @@ -181,9 +197,7 @@ where
SignatureSize<C>: ArrayLength<u8>,
{
fn from(secret_key: &SecretKey<C>) -> Self {
Self {
inner: secret_key.to_nonzero_scalar(),
}
secret_key.to_nonzero_scalar().into()
}
}

Expand All @@ -201,10 +215,28 @@ where
///
/// [RFC6979 § 3.2]: https://tools.ietf.org/html/rfc6979#section-3
fn try_sign_digest(&self, msg_digest: D) -> Result<Signature<C>> {
Ok(self.inner.try_sign_digest_rfc6979::<D>(msg_digest, &[])?.0)
Ok(self
.secret_scalar
.try_sign_digest_rfc6979::<D>(msg_digest, &[])?
.0)
}
}

#[cfg(feature = "verify")]
#[cfg_attr(docsrs, doc(cfg(feature = "verify")))]
impl<C> Keypair<Signature<C>> for SigningKey<C>
where
C: PrimeCurve + ProjectiveArithmetic + DigestPrimitive,
C::Digest: BlockSizeUser + FixedOutput<OutputSize = FieldSize<C>> + FixedOutputReset,
C::UInt: for<'a> From<&'a Scalar<C>>,
Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + Reduce<C::UInt> + SignPrimitive<C>,
AffinePoint<C>: VerifyPrimitive<C>,
Scalar<C>: Reduce<C::UInt>,
SignatureSize<C>: ArrayLength<u8>,
{
type VerifyingKey = VerifyingKey<C>;
}

impl<C> PrehashSigner<Signature<C>> for SigningKey<C>
where
C: PrimeCurve + ProjectiveArithmetic + DigestPrimitive,
Expand All @@ -217,7 +249,7 @@ where
let prehash = C::prehash_to_field_bytes(prehash)?;

Ok(self
.inner
.secret_scalar
.try_sign_prehashed_rfc6979::<C::Digest>(prehash, &[])?
.0)
}
Expand Down Expand Up @@ -253,7 +285,10 @@ where
) -> Result<Signature<C>> {
let mut ad = FieldBytes::<C>::default();
rng.fill_bytes(&mut ad);
Ok(self.inner.try_sign_digest_rfc6979::<D>(msg_digest, &ad)?.0)
Ok(self
.secret_scalar
.try_sign_digest_rfc6979::<D>(msg_digest, &ad)?
.0)
}
}

Expand All @@ -276,8 +311,13 @@ where
SignatureSize<C>: ArrayLength<u8>,
{
fn from(secret_scalar: NonZeroScalar<C>) -> Self {
#[cfg(feature = "verify")]
let public_key = PublicKey::from_secret_scalar(&secret_scalar);

Self {
inner: secret_scalar,
secret_scalar,
#[cfg(feature = "verify")]
verifying_key: public_key.into(),
}
}
}
Expand Down Expand Up @@ -335,7 +375,7 @@ where
SignatureSize<C>: ArrayLength<u8>,
{
fn to_pkcs8_der(&self) -> pkcs8::Result<SecretDocument> {
SecretKey::from(self.inner).to_pkcs8_der()
SecretKey::from(self.secret_scalar).to_pkcs8_der()
}
}

Expand Down
2 changes: 1 addition & 1 deletion ecdsa/src/verify.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ where
impl<C> Verifier<Signature<C>> for VerifyingKey<C>
where
C: PrimeCurve + ProjectiveArithmetic + DigestPrimitive,
C::Digest: Digest + FixedOutput<OutputSize = FieldSize<C>>,
C::Digest: FixedOutput<OutputSize = FieldSize<C>>,
AffinePoint<C>: VerifyPrimitive<C>,
Scalar<C>: Reduce<C::UInt>,
SignatureSize<C>: ArrayLength<u8>,
Expand Down