From be6d042d80a0e6ff0e2d059114a357b0f53d74df Mon Sep 17 00:00:00 2001
From: Kevin Lewi <klewi@fb.com>
Date: Thu, 28 Jan 2021 14:31:20 -0800
Subject: [PATCH] Restricting ciphersuite group to match hash output (#125)

---
 src/ciphersuite.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/ciphersuite.rs b/src/ciphersuite.rs
index e5f5024..adb44d4 100644
--- a/src/ciphersuite.rs
+++ b/src/ciphersuite.rs
@@ -9,6 +9,7 @@ use crate::{
     hash::Hash, key_exchange::traits::KeyExchange, keypair::KeyPair,
     map_to_curve::GroupWithMapToCurve, slow_hash::SlowHash,
 };
+use digest::Digest;
 
 use rand_core::{CryptoRng, RngCore};
 
@@ -25,7 +26,7 @@ pub trait CipherSuite {
     /// an extension trait PasswordToCurve that allows some customization on
     /// how to hash a password to a curve point. See `group::Group` and
     /// `map_to_curve::GroupWithMapToCurve`.
-    type Group: GroupWithMapToCurve;
+    type Group: GroupWithMapToCurve<UniformBytesLen = <Self::Hash as Digest>::OutputSize>;
     /// A key exchange protocol
     type KeyExchange: KeyExchange<Self::Hash, Self::Group>;
     /// The main hash function use (for HKDF computations and hashing transcripts)