From 44d53804c46c94a4543e0169210a282d8fc4b551 Mon Sep 17 00:00:00 2001
From: Bogdan Opanchuk <bogdan@opanchuk.net>
Date: Tue, 2 Mar 2021 15:05:27 -0800
Subject: [PATCH] Replace SHA3 with SHA2-256

---
 umbral-pre/Cargo.toml     |  1 -
 umbral-pre/src/curve.rs   |  6 +++---
 umbral-pre/src/hashing.rs | 10 +++++-----
 3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/umbral-pre/Cargo.toml b/umbral-pre/Cargo.toml
index 7cce5f48..31fd04b6 100644
--- a/umbral-pre/Cargo.toml
+++ b/umbral-pre/Cargo.toml
@@ -12,7 +12,6 @@ categories = ["cryptography", "no-std"]
 [dependencies]
 k256 = { version = "0.6", default-features = false, features = ["ecdsa", "arithmetic"] }
 blake2 = "0.9"
-sha3 = "0.9"
 sha2 = "0.9"
 chacha20poly1305 = "0.7"
 hkdf = "0.10"
diff --git a/umbral-pre/src/curve.rs b/umbral-pre/src/curve.rs
index b9be6a12..4803761b 100644
--- a/umbral-pre/src/curve.rs
+++ b/umbral-pre/src/curve.rs
@@ -267,7 +267,7 @@ impl SerializableToArray for PublicKey {
 #[cfg(test)]
 mod tests {
 
-    use sha3::Sha3_256;
+    use sha2::Sha256;
     use signature::digest::Digest;
 
     use super::{PublicKey, SecretKey};
@@ -294,11 +294,11 @@ mod tests {
     fn test_sign_and_verify() {
         let sk = SecretKey::random();
         let message = b"asdafdahsfdasdfasd";
-        let digest = Sha3_256::new().chain(message);
+        let digest = Sha256::new().chain(message);
         let signature = sk.sign_digest(digest);
 
         let pk = PublicKey::from_secret_key(&sk);
-        let digest = Sha3_256::new().chain(message);
+        let digest = Sha256::new().chain(message);
         assert!(pk.verify_digest(digest, &signature));
     }
 }
diff --git a/umbral-pre/src/hashing.rs b/umbral-pre/src/hashing.rs
index 927333f8..72899617 100644
--- a/umbral-pre/src/hashing.rs
+++ b/umbral-pre/src/hashing.rs
@@ -2,7 +2,7 @@ use blake2::VarBlake2b;
 use digest::{Digest, Update, VariableOutput};
 use generic_array::typenum::Unsigned;
 use generic_array::GenericArray;
-use sha3::Sha3_256;
+use sha2::Sha256;
 
 use crate::curve::{CurvePoint, CurveScalar, PublicKey, SecretKey, Signature};
 use crate::traits::SerializableToArray;
@@ -58,12 +58,12 @@ pub fn unsafe_hash_to_point(data: &[u8], label: &[u8]) -> Option<CurvePoint> {
     None
 }
 
-pub(crate) struct ScalarDigest(Sha3_256);
+pub(crate) struct ScalarDigest(Sha256);
 
 // TODO (#2): original uses ExtendedKeccak here
 impl ScalarDigest {
     pub fn new() -> Self {
-        Self(Sha3_256::new()).chain_bytes(b"hash_to_curvebn")
+        Self(Sha256::new()).chain_bytes(b"hash_to_curvebn")
     }
 
     fn chain_impl(self, bytes: &[u8]) -> Self {
@@ -95,11 +95,11 @@ impl ScalarDigest {
     }
 }
 
-pub(crate) struct SignatureDigest(Sha3_256);
+pub(crate) struct SignatureDigest(Sha256);
 
 impl SignatureDigest {
     pub fn new() -> Self {
-        Self(Sha3_256::new())
+        Self(Sha256::new())
     }
 
     fn chain_impl(self, bytes: &[u8]) -> Self {