refactor: add uint (U128) note to aztec-nr and remove OwnedNote from ValueNote

noir-projects/aztec-nr/Nargo.toml

@@ -6,4 +6,5 @@ members = [
   "compressed-string",
   "easy-private-state",
   "value-note",
+  "uint-note",
 ]

noir-projects/aztec-nr/uint-note/Nargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "uint_note"
+authors = ["aztec-labs"]
+compiler_version = ">=0.18.0"
+type = "lib"
+
+[dependencies]
+aztec = { path = "../aztec" }

noir-projects/aztec-nr/uint-note/src/lib.nr

@@ -0,0 +1 @@
+mod uint_note;

noir-projects/aztec-nr/uint-note/src/uint_note.nr

@@ -0,0 +1,110 @@
+use dep::aztec::{
+    generators::{Ga1 as G_amt, Ga2 as G_npk, Ga3 as G_rnd, G_slot},
+    prelude::{NoteHeader, NoteInterface, PrivateContext},
+    protocol_types::{
+    constants::GENERATOR_INDEX__NOTE_NULLIFIER, point::{Point, POINT_LENGTH}, scalar::Scalar,
+    hash::poseidon2_hash_with_separator, traits::Serialize
+},
+    note::utils::compute_note_hash_for_nullify, oracle::unsafe_rand::unsafe_rand,
+    keys::getters::get_nsk_app
+};
+use dep::std::{embedded_curve_ops::multi_scalar_mul, hash::from_field_unsafe};
+
+global UINT_NOTE_LEN: Field = 3; // 3 plus a header.
+global UINT_NOTE_BYTES_LEN: Field = 3 * 32 + 64;
+
+#[aztec(note)]
+struct UintNote {
+    // The integer stored by the note
+    value: U128,
+    // The nullifying public key hash is used with the nsk_app to ensure that the note can be privately spent.
+    npk_m_hash: Field,
+    // Randomness of the note to hide its contents
+    randomness: Field,
+}
+
+impl NoteInterface<UINT_NOTE_LEN, UINT_NOTE_BYTES_LEN> for UintNote {
+    fn compute_nullifier(self, context: &mut PrivateContext, note_hash_for_nullify: Field) -> Field {
+        let secret = context.request_nsk_app(self.npk_m_hash);
+        poseidon2_hash_with_separator([
+            note_hash_for_nullify,
+            secret
+        ],
+            GENERATOR_INDEX__NOTE_NULLIFIER as Field,
+        )
+    }
+
+    fn compute_nullifier_without_context(self) -> Field {
+        let note_hash_for_nullify = compute_note_hash_for_nullify(self);
+        let secret = get_nsk_app(self.npk_m_hash);
+        poseidon2_hash_with_separator([note_hash_for_nullify, secret],GENERATOR_INDEX__NOTE_NULLIFIER)
+    }
+
+    fn compute_note_hiding_point(self) -> Point {
+        // We use the unsafe version because the multi_scalar_mul will constrain the scalars.
+        let amount_scalar = from_field_unsafe(self.value.to_integer());
+        let npk_m_hash_scalar = from_field_unsafe(self.npk_m_hash);
+        let randomness_scalar = from_field_unsafe(self.randomness);
+        let slot_scalar = from_field_unsafe(self.header.storage_slot);
+        // We compute the note hiding point as:
+        //     `G_amt * amount + G_npk * npk_m_hash + G_rnd * randomness + G_slot * slot`
+        // instead of using pedersen or poseidon2 because it allows us to privately add and subtract from amount
+        // in public by leveraging homomorphism.
+        multi_scalar_mul(
+            [G_amt, G_npk, G_rnd, G_slot],
+            [amount_scalar, npk_m_hash_scalar, randomness_scalar, slot_scalar]
+        )
+    }
+}
+
+impl UintNote {
+    // TODO: Merge this func with `compute_note_hiding_point`. I (benesjan) didn't do it in the initial PR to not have
+    // to modify macros and all the related funcs in it.
+    fn to_note_hiding_point(self) -> UintNoteHidingPoint {
+        UintNoteHidingPoint::new(self.compute_note_hiding_point())
+    }
+}
+
+struct UintNoteHidingPoint {
+  inner: Point
+}
+
+impl UintNoteHidingPoint {
+    fn new(point: Point) -> Self {
+        Self { inner: point }
+    }
+
+    fn add_amount(&mut self, amount: U128) {
+        self.inner = multi_scalar_mul([G_amt], [from_field_unsafe(amount.to_integer())]) + self.inner;
+    }
+
+    fn add_npk_m_hash(&mut self, npk_m_hash: Field) {
+        self.inner = multi_scalar_mul([G_npk], [from_field_unsafe(npk_m_hash)]) + self.inner;
+    }
+
+    fn add_randomness(&mut self, randomness: Field) {
+        self.inner = multi_scalar_mul([G_rnd], [from_field_unsafe(randomness)]) + self.inner;
+    }
+
+    fn add_slot(&mut self, slot: Field) {
+        self.inner = multi_scalar_mul([G_slot], [from_field_unsafe(slot)]) + self.inner;
+    }
+
+    fn finalize(self) -> Field {
+        self.inner.x
+    }
+}
+
+impl Serialize<POINT_LENGTH> for UintNoteHidingPoint {
+    fn serialize(self) -> [Field; POINT_LENGTH] {
+        self.inner.serialize()
+    }
+}
+
+impl Eq for UintNote {
+    fn eq(self, other: Self) -> bool {
+        (self.value == other.value) &
+        (self.npk_m_hash == other.npk_m_hash) &
+        (self.randomness == other.randomness)
+    }
+}

noir-projects/aztec-nr/value-note/src/value_note.nr

@@ -13,11 +13,6 @@ global VALUE_NOTE_LEN: Field = 3; // 3 plus a header.
 // VALUE_NOTE_LEN * 32 + 32(storage_slot as bytes) + 32(note_type_id as bytes)
 global VALUE_NOTE_BYTES_LEN: Field = 3 * 32 + 64;
 
-trait OwnedNote {
-    fn new(amount: U128, owner_npk_m_hash: Field) -> Self;
-    fn get_amount(self) -> U128;
-}
-
 // docs:start:value-note-def
 #[aztec(note)]
 struct ValueNote {
@@ -105,21 +100,6 @@ impl Eq for ValueNote {
     }
 }
 
-impl OwnedNote for ValueNote {
-    fn new(value: U128, owner_npk_m_hash: Field) -> Self {
-        Self {
-            value: value.to_field(),
-            npk_m_hash: owner_npk_m_hash,
-            randomness: unsafe_rand(),
-            header: NoteHeader::empty(),
-        }
-    }
-
-    fn get_amount(self) -> U128 {
-        U128::from_field(self.value)
-    }
-}
-
 struct ValueNoteHidingPoint {
   inner: Point
 }