Move ExpandMsg lifetime to expander

Author: daxpedda

elliptic-curve/src/hash2curve/group_digest.rs

@@ -35,9 +35,9 @@ pub trait GroupDigest: CurveArithmetic<ProjectivePoint: CofactorGroup, Scalar: F
     ///
     /// [`ExpandMsgXmd`]: crate::hash2curve::ExpandMsgXmd
     /// [`ExpandMsgXof`]: crate::hash2curve::ExpandMsgXof
-    fn hash_from_bytes<'a, X>(msg: &[&[u8]], dst: &'a [&'a [u8]]) -> Result<ProjectivePoint<Self>>
+    fn hash_from_bytes<X>(msg: &[&[u8]], dst: &[&[u8]]) -> Result<ProjectivePoint<Self>>
     where
-        X: ExpandMsg<'a, Self::K>,
+        X: ExpandMsg<Self::K>,
     {
         let mut u = [Self::FieldElement::default(), Self::FieldElement::default()];
         hash_to_field::<X, _, _>(msg, dst, &mut u)?;
@@ -75,9 +75,9 @@ pub trait GroupDigest: CurveArithmetic<ProjectivePoint: CofactorGroup, Scalar: F
     ///
     /// [`ExpandMsgXmd`]: crate::hash2curve::ExpandMsgXmd
     /// [`ExpandMsgXof`]: crate::hash2curve::ExpandMsgXof
-    fn encode_from_bytes<'a, X>(msg: &[&[u8]], dst: &'a [&'a [u8]]) -> Result<ProjectivePoint<Self>>
+    fn encode_from_bytes<X>(msg: &[&[u8]], dst: &[&[u8]]) -> Result<ProjectivePoint<Self>>
     where
-        X: ExpandMsg<'a, Self::K>,
+        X: ExpandMsg<Self::K>,
     {
         let mut u = [Self::FieldElement::default()];
         hash_to_field::<X, _, _>(msg, dst, &mut u)?;
@@ -98,9 +98,9 @@ pub trait GroupDigest: CurveArithmetic<ProjectivePoint: CofactorGroup, Scalar: F
     ///
     /// [`ExpandMsgXmd`]: crate::hash2curve::ExpandMsgXmd
     /// [`ExpandMsgXof`]: crate::hash2curve::ExpandMsgXof
-    fn hash_to_scalar<'a, X>(msg: &[&[u8]], dst: &'a [&'a [u8]]) -> Result<Self::Scalar>
+    fn hash_to_scalar<X>(msg: &[&[u8]], dst: &[&[u8]]) -> Result<Self::Scalar>
     where
-        X: ExpandMsg<'a, Self::K>,
+        X: ExpandMsg<Self::K>,
     {
         let mut u = [Self::Scalar::default()];
         hash_to_field::<X, _, _>(msg, dst, &mut u)?;

elliptic-curve/src/hash2curve/hash2field.rs

@@ -37,13 +37,9 @@ pub trait FromOkm {
 /// [`ExpandMsgXmd`]: crate::hash2field::ExpandMsgXmd
 /// [`ExpandMsgXof`]: crate::hash2field::ExpandMsgXof
 #[doc(hidden)]
-pub fn hash_to_field<'a, E, K, T>(
-    data: &[&[u8]],
-    domain: &'a [&'a [u8]],
-    out: &mut [T],
-) -> Result<()>
+pub fn hash_to_field<E, K, T>(data: &[&[u8]], domain: &[&[u8]], out: &mut [T]) -> Result<()>
 where
-    E: ExpandMsg<'a, K>,
+    E: ExpandMsg<K>,
     T: FromOkm + Default,
 {
     let len_in_bytes = T::Length::to_usize()

elliptic-curve/src/hash2curve/hash2field/expand_msg.rs

@@ -23,19 +23,19 @@ const MAX_DST_LEN: usize = 255;
 ///
 /// # Errors
 /// See implementors of [`ExpandMsg`] for errors.
-pub trait ExpandMsg<'a, K> {
+pub trait ExpandMsg<K> {
     /// Type holding data for the [`Expander`].
-    type Expander: Expander + Sized;
+    type Expander<'dst>: Expander + Sized;
 
     /// Expands `msg` to the required number of bytes.
     ///
     /// Returns an expander that can be used to call `read` until enough
     /// bytes have been consumed
-    fn expand_message(
+    fn expand_message<'dst>(
         msg: &[&[u8]],
-        dst: &'a [&'a [u8]],
+        dst: &'dst [&[u8]],
         len_in_bytes: NonZero<usize>,
-    ) -> Result<Self::Expander>;
+    ) -> Result<Self::Expander<'dst>>;
 }
 
 /// Expander that, call `read` until enough bytes have been consumed.

elliptic-curve/src/hash2curve/hash2field/expand_msg/xmd.rs

@@ -27,7 +27,7 @@ where
     HashT::OutputSize: IsLess<U256, Output = True>,
     HashT::OutputSize: IsLessOrEqual<HashT::BlockSize, Output = True>;
 
-impl<'a, HashT, K> ExpandMsg<'a, K> for ExpandMsgXmd<HashT>
+impl<HashT, K> ExpandMsg<K> for ExpandMsgXmd<HashT>
 where
     HashT: BlockSizeUser + Default + FixedOutput + HashMarker,
     // If DST is larger than 255 bytes, the length of the computed DST will depend on the output
@@ -42,13 +42,13 @@ where
     K: Mul<U2>,
     HashT::OutputSize: IsGreaterOrEqual<Prod<K, U2>, Output = True>,
 {
-    type Expander = ExpanderXmd<'a, HashT>;
+    type Expander<'dst> = ExpanderXmd<'dst, HashT>;
 
-    fn expand_message(
+    fn expand_message<'dst>(
         msg: &[&[u8]],
-        dst: &'a [&'a [u8]],
+        dst: &'dst [&[u8]],
         len_in_bytes: NonZero<usize>,
-    ) -> Result<Self::Expander> {
+    ) -> Result<Self::Expander<'dst>> {
         let len_in_bytes_u16 = u16::try_from(len_in_bytes.get()).map_err(|_| Error)?;
 
         // `255 * <b_in_bytes>` can not exceed `u16::MAX`
@@ -221,7 +221,7 @@ mod test {
             assert_message::<HashT>(self.msg, domain, L::to_u16(), self.msg_prime);
 
             let dst = [dst];
-            let mut expander = <ExpandMsgXmd<HashT> as ExpandMsg<'_, U4>>::expand_message(
+            let mut expander = <ExpandMsgXmd<HashT> as ExpandMsg<U4>>::expand_message(
                 &[self.msg],
                 &dst,
                 NonZero::new(L::to_usize()).ok_or(Error)?,

elliptic-curve/src/hash2curve/hash2field/expand_msg/xof.rs

@@ -34,20 +34,20 @@ where
     }
 }
 
-impl<'a, HashT, K> ExpandMsg<'a, K> for ExpandMsgXof<HashT>
+impl<HashT, K> ExpandMsg<K> for ExpandMsgXof<HashT>
 where
     HashT: Default + ExtendableOutput + Update + HashMarker,
     // If DST is larger than 255 bytes, the length of the computed DST is calculated by `K * 2`.
     // https://www.rfc-editor.org/rfc/rfc9380.html#section-5.3.1-2.1
     K: Mul<U2, Output: ArraySize + IsLess<U256, Output = True>>,
 {
-    type Expander = Self;
+    type Expander<'dst> = Self;
 
-    fn expand_message(
+    fn expand_message<'dst>(
         msg: &[&[u8]],
-        dst: &'a [&'a [u8]],
+        dst: &'dst [&[u8]],
         len_in_bytes: NonZero<usize>,
-    ) -> Result<Self::Expander> {
+    ) -> Result<Self::Expander<'dst>> {
         let len_in_bytes = u16::try_from(len_in_bytes.get()).map_err(|_| Error)?;
 
         let domain = Domain::<Prod<K, U2>>::xof::<HashT>(dst)?;
@@ -119,7 +119,7 @@ mod test {
         {
             assert_message(self.msg, domain, L::to_u16(), self.msg_prime);
 
-            let mut expander = <ExpandMsgXof<HashT> as ExpandMsg<'_, U16>>::expand_message(
+            let mut expander = <ExpandMsgXof<HashT> as ExpandMsg<U16>>::expand_message(
                 &[self.msg],
                 &[dst],
                 NonZero::new(L::to_usize()).ok_or(Error)?,

elliptic-curve/src/oprf.rs

@@ -26,5 +26,5 @@ pub trait OprfParameters: GroupDigest + PrimeCurve {
     /// and `HashToScalar` as defined in [section 4 of RFC9497][oprf].
     ///
     /// [oprf]: https://www.rfc-editor.org/rfc/rfc9497.html#name-ciphersuites
-    type ExpandMsg: for<'a> ExpandMsg<'a, <Self as GroupDigest>::K>;
+    type ExpandMsg: ExpandMsg<<Self as GroupDigest>::K>;
 }