Amend

Cargo.toml

@@ -14,6 +14,7 @@ default = []
 [dependencies]
 base64 = "0.22.1"
 bitcoin = "0.32.5"
+sha2 = "0.10.8"
 snafu = { version =  "0.8.5", default-features = false, features = ["rust_1_61", "std"] }
 
 [dev-dependencies]

src/lib.rs

@@ -1,6 +1,5 @@
 use {
   base64::{engine::general_purpose, Engine},
-  bitcoin::hashes::{sha256, Hash},
   bitcoin::{
     absolute::LockTime,
     address::AddressData,
@@ -18,6 +17,7 @@ use {
     Transaction, TxIn, TxOut, Witness,
   },
   error::Error,
+  sha2::{Digest, Sha256},
   snafu::{ResultExt, Snafu},
   std::str::FromStr,
 };
@@ -51,12 +51,12 @@ mod tests {
   #[test]
   fn message_hashes_are_correct() {
     assert_eq!(
-      hex::encode(message_hash("".as_bytes())),
+      hex::encode(tagged_hash(BIP322_TAG, "")),
       "c90c269c4f8fcbe6880f72a721ddfbf1914268a794cbb21cfafee13770ae19f1"
     );
 
     assert_eq!(
-      hex::encode(message_hash("Hello World".as_bytes())),
+      hex::encode(tagged_hash(BIP322_TAG, "Hello World")),
       "f0eb03b1a75ac6d9847f55c624a99169b5dccba2a31f5b23bea77ba270de0a7a"
     );
   }

src/util.rs

@@ -1,16 +1,16 @@
 use super::*;
 
-const TAG: &str = "BIP0322-signed-message";
+pub const BIP322_TAG: &str = "BIP0322-signed-message";
 
 /// Create the tagged message hash.
-pub fn message_hash(message: &[u8]) -> Vec<u8> {
-  let mut tag_hash = sha256::Hash::hash(TAG.as_bytes()).to_byte_array().to_vec();
-  tag_hash.extend(tag_hash.clone());
-  tag_hash.extend(message);
-
-  sha256::Hash::hash(tag_hash.as_slice())
-    .to_byte_array()
-    .to_vec()
+pub fn tagged_hash(tag: &str, message: impl AsRef<[u8]>) -> [u8; 32] {
+  let tag_hash = Sha256::new().chain_update(tag).finalize();
+  Sha256::new()
+    .chain_update(tag_hash)
+    .chain_update(tag_hash)
+    .chain_update(message)
+    .finalize()
+    .into()
 }
 
 /// Create the `to_spend` transaction.
@@ -27,7 +27,12 @@ pub fn create_to_spend(address: &Address, message: &[u8]) -> Result<Transaction>
       },
       script_sig: script::Builder::new()
         .push_int(0)
-        .push_slice::<&PushBytes>(message_hash(message).as_slice().try_into().unwrap())
+        .push_slice::<&PushBytes>(
+          tagged_hash(BIP322_TAG, message)
+            .as_slice()
+            .try_into()
+            .unwrap(),
+        )
         .into_script(),
       sequence: Sequence(0),
       witness: Witness::new(),