Update derivation of the rho value in Issue Notes

src/issuance.rs

@@ -298,6 +298,37 @@ impl<T: IssueAuth> IssueBundle<T> {
             authorization: map_auth(authorization),
         }
     }
+
+    /// Returns the reference notes for the `IssueBundle`.
+    pub fn get_reference_notes(self) -> HashMap<AssetBase, Note> {
+        let mut reference_notes = HashMap::new();
+        self.actions.iter().for_each(|action| {
+            action.notes.iter().for_each(|note| {
+                if (note.recipient() == ReferenceKeys::recipient())
+                    && (note.value() == NoteValue::zero())
+                {
+                    reference_notes.insert(note.asset(), *note);
+                }
+            })
+        });
+        reference_notes
+    }
+
+    /// Compute the correct `\rho` value for each note in the bundle.
+    pub fn finalize(&mut self, nullifier: Nullifier) {
+        self.actions
+            .iter_mut()
+            .enumerate()
+            .for_each(|(index_action, action)| {
+                action
+                    .notes
+                    .iter_mut()
+                    .enumerate()
+                    .for_each(|(index_note, note)| {
+                        note.update_rho_for_issuance_note(nullifier, index_action, index_note);
+                    });
+            });
+    }
 }
 
 impl IssueBundle<Unauthorized> {
@@ -468,23 +499,6 @@ impl IssueBundle<Unauthorized> {
     }
 }
 
-impl<T: IssueAuth> IssueBundle<T> {
-    /// Returns the reference notes for the `IssueBundle`.
-    pub fn get_reference_notes(self) -> HashMap<AssetBase, Note> {
-        let mut reference_notes = HashMap::new();
-        self.actions.iter().for_each(|action| {
-            action.notes.iter().for_each(|note| {
-                if (note.recipient() == ReferenceKeys::recipient())
-                    && (note.value() == NoteValue::zero())
-                {
-                    reference_notes.insert(note.asset(), *note);
-                }
-            })
-        });
-        reference_notes
-    }
-}
-
 fn create_reference_note(asset: AssetBase, mut rng: impl RngCore) -> Note {
     Note::new(
         ReferenceKeys::recipient(),

src/note.rs

@@ -1,4 +1,5 @@
 //! Data structures used for note construction.
+use blake2b_simd::Params;
 use core::fmt;
 use memuse::DynamicUsage;
 
@@ -22,6 +23,8 @@ pub use self::commitment::{ExtractedNoteCommitment, NoteCommitment};
 pub(crate) mod nullifier;
 pub use self::nullifier::Nullifier;
 
+const ZSA_ISSUE_NOTE_RHO_PERSONALIZATION: &[u8; 16] = b"ZSA_IssueNoteRho";
+
 /// The randomness used to construct a note.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Rho(pallas::Base);
@@ -345,6 +348,31 @@ impl Note {
             ..self
         }
     }
+
+    /// Update the rho value of the issuance note.
+    pub(crate) fn update_rho_for_issuance_note(
+        &mut self,
+        nullifier: Nullifier,
+        index_action: usize,
+        index_note: usize,
+    ) {
+        let index_action_bytes: [u8; 4] = (index_action.try_into().unwrap() as u32).to_le_bytes();
+        let index_note_bytes: [u8; 4] = (index_note.try_into().unwrap() as u32).to_le_bytes();
+        self.rho = Rho(to_base(
+            Params::new()
+                .hash_length(64)
+                .personal(ZSA_ISSUE_NOTE_RHO_PERSONALIZATION)
+                .to_state()
+                .update(&nullifier.to_bytes())
+                .update(&[0x84])
+                .update(index_action_bytes.as_ref())
+                .update(index_note_bytes.as_ref())
+                .finalize()
+                .as_bytes()
+                .try_into()
+                .unwrap(),
+        ));
+    }
 }
 
 /// An encrypted note.