Loosen Hash constraints further

Author: daxpedda

src/ciphersuite.rs

@@ -12,14 +12,14 @@ use digest::core_api::BlockSizeUser;
 use digest::{FixedOutput, HashMarker, OutputSizeUser};
 use elliptic_curve::VoprfParameters;
 use elliptic_curve::hash2curve::{ExpandMsg, ExpandMsgXmd};
-use hybrid_array::typenum::{IsLess, IsLessOrEqual, U256};
+use hybrid_array::typenum::{IsLess, IsLessOrEqual, U256, U65536};
 
 use crate::Group;
 
 /// Configures the underlying primitives used in VOPRF
 pub trait CipherSuite
 where
-    <Self::Hash as OutputSizeUser>::OutputSize: IsLess<U256>,
+    <Self::Hash as OutputSizeUser>::OutputSize: IsLess<U65536>,
 {
     /// The ciphersuite identifier as dictated by
     /// <https://www.rfc-editor.org/rfc/rfc9497>
@@ -43,7 +43,7 @@ where
     T: Group,
     T::Hash: BlockSizeUser + Default + FixedOutput + HashMarker,
     <T::Hash as OutputSizeUser>::OutputSize:
-        IsLess<U256> + IsLessOrEqual<<T::Hash as BlockSizeUser>::BlockSize>,
+        IsLess<U256> + IsLess<U65536> + IsLessOrEqual<<T::Hash as BlockSizeUser>::BlockSize>,
 {
     const ID: &'static str = T::ID;
 

src/common.rs

@@ -13,7 +13,7 @@ use core::ops::Add;
 
 use derive_where::derive_where;
 use digest::{Digest, Output};
-use hybrid_array::typenum::{IsLess, U9, U256, Unsigned};
+use hybrid_array::typenum::{IsLess, U9, U65536, Unsigned};
 use hybrid_array::{Array, ArrayN, ArraySize};
 use rand_core::{TryCryptoRng, TryRngCore};
 use subtle::ConstantTimeEq;
@@ -441,7 +441,7 @@ pub(crate) fn server_evaluate_hash_input<CS: CipherSuite>(
             .chain_update(info.as_ref());
     }
     Ok(hash
-        .chain_update(i2osp_2(issued_element.len()).map_err(|_| Error::Input)?)
+        .chain_update(i2osp_2_array(&issued_element))
         .chain_update(issued_element)
         .chain_update(STR_FINALIZE)
         .finalize())
@@ -515,6 +515,6 @@ pub(crate) fn i2osp_2(input: usize) -> Result<[u8; 2], InternalError> {
         .map_err(|_| InternalError::I2osp)
 }
 
-pub(crate) fn i2osp_2_array<L: ArraySize + IsLess<U256>>(_: &Array<u8, L>) -> ArrayN<u8, 2> {
+pub(crate) fn i2osp_2_array<L: ArraySize + IsLess<U65536>>(_: &Array<u8, L>) -> ArrayN<u8, 2> {
     L::U16.to_be_bytes().into()
 }

src/group/elliptic_curve.rs

@@ -14,7 +14,7 @@ use elliptic_curve::sec1::{FromEncodedPoint, ModulusSize, ToEncodedPoint};
 use elliptic_curve::{
     AffinePoint, Field, FieldBytesSize, Group as _, ProjectivePoint, PublicKey, Scalar, SecretKey,
 };
-use hybrid_array::typenum::Sum;
+use hybrid_array::typenum::{IsLess, Sum, U65536};
 use hybrid_array::{Array, ArraySize};
 use rand_core::{TryCryptoRng, TryRngCore};
 
@@ -28,6 +28,7 @@ impl<C> Group for C
 where
     C: GroupDigest,
     ProjectivePoint<Self>: CofactorGroup + ToEncodedPoint<Self>,
+    ElemLen<Self>: IsLess<U65536>,
     ScalarLen<Self>: ModulusSize,
     AffinePoint<Self>: FromEncodedPoint<Self> + ToEncodedPoint<Self>,
     Scalar<Self>: FromOkm,

src/group/mod.rs

@@ -21,7 +21,7 @@ use core::ops::{Add, Mul, Sub};
 use ::elliptic_curve::hash2curve::ExpandMsg;
 #[cfg(feature = "decaf448")]
 pub use decaf::Decaf448;
-use hybrid_array::typenum::Sum;
+use hybrid_array::typenum::{IsLess, Sum, U65536};
 use hybrid_array::{Array, ArraySize};
 use rand_core::{TryCryptoRng, TryRngCore};
 #[cfg(feature = "ristretto255")]
@@ -50,7 +50,7 @@ where
         + for<'a> Mul<&'a Self::Scalar, Output = Self::Elem>;
 
     /// The byte length necessary to represent group elements
-    type ElemLen: ArraySize + 'static;
+    type ElemLen: ArraySize + IsLess<U65536> + 'static;
 
     /// The type of base field scalars
     type Scalar: ConstantTimeEq