[WIP] elliptic-curve: simplify EncodedPoint

Changes `EncodedPoint<C>` to be backed by a byte slice which is always
the size of a SEC-1 encoded uncompressed point, eliminating the previous
`CompressedPoint` and `UncompressedPoint` types.

This allows for simplified trait bounds as we no longer need to care
about `CompressedPointSize` in the bounds.

elliptic-curve/Cargo.toml

@@ -21,6 +21,9 @@ rand_core = { version = "0.5", optional = true, default-features = false }
 subtle = { version = "2.2", default-features = false }
 zeroize = { version = "1", optional = true, default-features = false }
 
+[dev-dependencies]
+hex-literal = "0.2"
+
 [features]
 default = ["rand"]
 ecdh = ["rand", "weierstrass", "zeroize"]

elliptic-curve/src/ecdh.rs

@@ -22,17 +22,14 @@
 
 use crate::{
  consts::U1,
+ generic_array::ArrayLength,
  point::Generator,
  scalar::NonZeroScalar,
- sec1::{
- self, CompressedPoint, CompressedPointSize, FromEncodedPoint, UncompressedPoint,
- UncompressedPointSize,
- },
+ sec1::{self, FromEncodedPoint, UncompressedPointSize, UntaggedPointSize},
  weierstrass::Curve,
  Arithmetic, ElementBytes, Error, Generate,
 };
 use core::ops::{Add, Mul};
-use generic_array::{typenum::Unsigned, ArrayLength, GenericArray};
 use rand_core::{CryptoRng, RngCore};
 use zeroize::Zeroize;
 
@@ -58,11 +55,8 @@ where
  C: Curve + Arithmetic,
  C::Scalar: Clone + Generate + Zeroize,
  C::AffinePoint: FromEncodedPoint<C> + Mul<NonZeroScalar<C>, Output = C::AffinePoint> + Zeroize,
- C::ElementSize: Add<U1>,
- <C::ElementSize as Add>::Output: Add<U1>,
- CompressedPoint<C>: From<C::AffinePoint>,
- UncompressedPoint<C>: From<C::AffinePoint>,
- CompressedPointSize<C>: ArrayLength<u8>,
+ PublicKey<C>: From<C::AffinePoint>,
+ UntaggedPointSize<C>: Add<U1> + ArrayLength<u8>,
  UncompressedPointSize<C>: ArrayLength<u8>,
 {
  /// Generate a new [`EphemeralSecret`].
@@ -75,14 +69,8 @@ where
  /// Get the public key associated with this ephemeral secret.
  ///
  /// The `compress` flag enables point compression.
- pub fn public_key(&self, compress: bool) -> PublicKey<C> {
- let affine_point = C::AffinePoint::generator() * self.scalar.clone();
-
- if compress {
- PublicKey::Compressed(affine_point.into())
- } else {
- PublicKey::Uncompressed(affine_point.into())
- }
+ pub fn public_key(&self) -> PublicKey<C> {
+ PublicKey::from(C::AffinePoint::generator() * self.scalar.clone())
  }
 
  /// Compute a Diffie-Hellman shared secret from an ephemeral secret and the
@@ -104,15 +92,12 @@ where
  C: Curve + Arithmetic,
  C::Scalar: Clone + Generate + Zeroize,
  C::AffinePoint: FromEncodedPoint<C> + Mul<NonZeroScalar<C>, Output = C::AffinePoint> + Zeroize,
- C::ElementSize: Add<U1>,
- <C::ElementSize as Add>::Output: Add<U1>,
- CompressedPoint<C>: From<C::AffinePoint>,
- UncompressedPoint<C>: From<C::AffinePoint>,
- CompressedPointSize<C>: ArrayLength<u8>,
+ PublicKey<C>: From<C::AffinePoint>,
+ UntaggedPointSize<C>: Add<U1> + ArrayLength<u8>,
  UncompressedPointSize<C>: ArrayLength<u8>,
 {
  fn from(ephemeral_secret: &EphemeralSecret<C>) -> Self {
- ephemeral_secret.public_key(C::COMPRESS_POINTS)
+ ephemeral_secret.public_key()
  }
 }
 
@@ -158,17 +143,13 @@ impl<C> SharedSecret<C>
 where
  C: Curve + Arithmetic,
  C::AffinePoint: Zeroize,
- C::ElementSize: Add<U1>,
- <C::ElementSize as Add>::Output: Add<U1>,
+ UntaggedPointSize<C>: Add<U1> + ArrayLength<u8>,
  UncompressedPointSize<C>: ArrayLength<u8>,
 {
  /// Create a new shared secret from the given uncompressed curve point
- fn new(mut serialized_point: UncompressedPoint<C>) -> Self {
- let secret_bytes = GenericArray::clone_from_slice(
- &serialized_point.as_ref()[1..(1 + C::ElementSize::to_usize())],
- );
-
- serialized_point.zeroize();
+ fn new(mut encoded_point: sec1::EncodedPoint<C>) -> Self {
+ let secret_bytes = encoded_point.x().clone();
+ encoded_point.zeroize();
  Self { secret_bytes }
  }