From 0ac67851120e535e54798708668b8cf487f866e5 Mon Sep 17 00:00:00 2001
From: polydez <155382956+polydez@users.noreply.github.com>
Date: Tue, 2 Jul 2024 19:44:42 +0500
Subject: [PATCH] Implemented `OutputNote::hash` (#782)

* feat: implement `OutputNote::hash`

* fix: review comments
---
 objects/src/notes/header.rs        | 17 +++++++++++++++--
 objects/src/notes/mod.rs           |  2 +-
 objects/src/transaction/outputs.rs | 10 ++++++++--
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/objects/src/notes/header.rs b/objects/src/notes/header.rs
index feb6feb01..4cc7247a2 100644
--- a/objects/src/notes/header.rs
+++ b/objects/src/notes/header.rs
@@ -41,13 +41,26 @@ impl NoteHeader {
     ///
     /// > hash(NOTE_ID || NOTE_METADATA)
     ///
-    /// This value is used primarily for authenticating notes consumed when the are consumed
+    /// This value is used primarily for authenticating notes consumed when they are consumed
     /// in a transaction.
     pub fn hash(&self) -> Digest {
-        Hasher::merge(&[self.id().inner(), Word::from(self.metadata()).into()])
+        compute_note_hash(self.id(), self.metadata())
     }
 }
 
+// UTILITIES
+// ================================================================================================
+
+/// Returns a commitment to the note and its metadata.
+///
+/// > hash(NOTE_ID || NOTE_METADATA)
+///
+/// This value is used primarily for authenticating notes consumed when they are consumed
+/// in a transaction.
+pub fn compute_note_hash(id: NoteId, metadata: &NoteMetadata) -> Digest {
+    Hasher::merge(&[id.inner(), Word::from(metadata).into()])
+}
+
 // CONVERSIONS FROM NOTE HEADER
 // ================================================================================================
 
diff --git a/objects/src/notes/mod.rs b/objects/src/notes/mod.rs
index 6d25cf219..e7dd6aca6 100644
--- a/objects/src/notes/mod.rs
+++ b/objects/src/notes/mod.rs
@@ -21,7 +21,7 @@ mod details;
 pub use details::NoteDetails;
 
 mod header;
-pub use header::NoteHeader;
+pub use header::{compute_note_hash, NoteHeader};
 
 mod inputs;
 pub use inputs::NoteInputs;
diff --git a/objects/src/transaction/outputs.rs b/objects/src/transaction/outputs.rs
index d5d4f5a52..1e0c04ac8 100644
--- a/objects/src/transaction/outputs.rs
+++ b/objects/src/transaction/outputs.rs
@@ -6,10 +6,9 @@ use vm_processor::DeserializationError;
 
 use crate::{
     accounts::AccountStub,
-    notes::{Note, NoteAssets, NoteHeader, NoteId, NoteMetadata, PartialNote},
+    notes::{compute_note_hash, Note, NoteAssets, NoteHeader, NoteId, NoteMetadata, PartialNote},
     Digest, Felt, Hasher, TransactionOutputError, Word, MAX_OUTPUT_NOTES_PER_TX,
 };
-
 // TRANSACTION OUTPUTS
 // ================================================================================================
 
@@ -205,6 +204,13 @@ impl OutputNote {
             _ => self.clone(),
         }
     }
+
+    /// Returns a commitment to the note and its metadata.
+    ///
+    /// > hash(NOTE_ID || NOTE_METADATA)
+    pub fn hash(&self) -> Digest {
+        compute_note_hash(self.id(), self.metadata())
+    }
 }
 
 // CONVERSIONS