feat: destroy_note_unsafe (#7891)

Fixes #7831

Gate diff: 82803 - 78619 = **4184** gates saved

docs/docs/guides/developer_guides/smart_contracts/writing_contracts/notes/custom_note.md

@@ -25,11 +25,11 @@ You will need to implement a note interface for your note. Most of this is autom
 
 #include_code note_interface noir-projects/aztec-nr/aztec/src/note/note_interface.nr rust
 
-You will need to implement the functions `compute_note_hash_and_nullifier()` and `compute_note_hash_and_nullifier_without_context()` which tells Aztec how to compute nullifiers for your note.
+You will need to implement the functions `compute_nullifier(...)` and `compute_nullifier_without_context()` which tells Aztec how to compute nullifiers for your note.
 
 #include_code note_interface noir-projects/noir-contracts/contracts/docs_example_contract/src/types/card_note.nr rust
 
-In this example, these functions compute the note hash by using `compute_note_hash_for_consumption` and then generate a nullifier by hashing this note hash together with a secret.
+In this example, these functions compute the note hash by using `compute_note_hash_for_nullify` and then generate a nullifier by hashing this note hash together with a secret.
 
 ### Methods
 

docs/docs/migration_notes.md

@@ -8,6 +8,57 @@ Aztec is in full-speed development. Literally every version breaks compatibility
 
 ## 0.48.0
 
+### NoteInterface changes
+
+`compute_note_hash_and_nullifier*` functions were renamed as `compute_nullifier*` and the `compute_nullifier` function now takes `note_hash_for_nullify` as an argument (this allowed us to reduce gate counts and the hash was typically computed before). Also `compute_note_hash_for_consumption` function was renamed as `compute_note_hash_for_nullify`.
+
+```diff
+impl NoteInterface<VALUE_NOTE_LEN, VALUE_NOTE_BYTES_LEN> for ValueNote {
+-    fn compute_note_hash_and_nullifier(self, context: &mut PrivateContext) -> (Field, Field) {
+-        let note_hash_for_nullify = compute_note_hash_for_consumption(self);
+-        let secret = context.request_nsk_app(self.npk_m_hash);
+-        let nullifier = poseidon2_hash_with_separator([
+-            note_hash_for_nullify,
+-            secret,
+-        ],
+-            GENERATOR_INDEX__NOTE_NULLIFIER as Field,
+-        );
+-        (note_hash_for_nullify, nullifier)
+-    }
+-    fn compute_note_hash_and_nullifier_without_context(self) -> (Field, Field) {
+-        let note_hash_for_nullify = compute_note_hash_for_consumption(self);
+-        let secret = get_nsk_app(self.npk_m_hash);
+-        let nullifier = poseidon2_hash_with_separator([
+-            note_hash_for_nullify,
+-            secret,
+-        ],
+-            GENERATOR_INDEX__NOTE_NULLIFIER as Field,
+-        );
+-        (note_hash_for_nullify, nullifier)
+-    }
+
++    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 as Field,
++        )
++    }
+}
+```
+
 ### Fee Juice rename
 
 The name of the canonical Gas contract has changed to Fee Juice. Update noir code:

noir-projects/aztec-nr/address-note/src/address_note.nr

@@ -3,7 +3,7 @@ use dep::aztec::{
     address::AztecAddress, traits::Empty, constants::GENERATOR_INDEX__NOTE_NULLIFIER,
     hash::poseidon2_hash_with_separator
 },
-    note::{note_header::NoteHeader, note_interface::NoteInterface, utils::compute_note_hash_for_consumption},
+    note::{note_header::NoteHeader, note_interface::NoteInterface, utils::compute_note_hash_for_nullify},
     oracle::unsafe_rand::unsafe_rand, keys::getters::get_nsk_app, context::PrivateContext
 };
 
@@ -25,28 +25,25 @@ struct AddressNote {
 
 impl NoteInterface<ADDRESS_NOTE_LEN, ADDRESS_NOTE_BYTES_LEN> for AddressNote {
 
-    fn compute_note_hash_and_nullifier(self, context: &mut PrivateContext) -> (Field, Field) {
-        let note_hash_for_nullify = compute_note_hash_for_consumption(self);
+    fn compute_nullifier(self, context: &mut PrivateContext, note_hash_for_nullify: Field) -> Field {
         let secret = context.request_nsk_app(self.npk_m_hash);
-        let nullifier = poseidon2_hash_with_separator([
+        poseidon2_hash_with_separator([
             note_hash_for_nullify,
             secret
         ],
             GENERATOR_INDEX__NOTE_NULLIFIER as Field,
-        );
-        (note_hash_for_nullify, nullifier)
+        )
     }
 
-    fn compute_note_hash_and_nullifier_without_context(self) -> (Field, Field) {
-        let note_hash_for_nullify = compute_note_hash_for_consumption(self);
+    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);
-        let nullifier = poseidon2_hash_with_separator([
+        poseidon2_hash_with_separator([
             note_hash_for_nullify,
             secret
         ],
             GENERATOR_INDEX__NOTE_NULLIFIER as Field,
-        );
-        (note_hash_for_nullify, nullifier)
+        )
     }
 }
 

noir-projects/aztec-nr/aztec/src/encrypted_logs/incoming_body.nr

@@ -71,11 +71,13 @@ mod test {
 
         fn set_header(&mut self, header: NoteHeader) {self.header = header; }
 
-        fn compute_note_hash_and_nullifier(_self: Self, _context: &mut PrivateContext) -> (Field, Field) {
-            (1, 1)
+        fn compute_nullifier(_self: Self, _context: &mut PrivateContext, _note_hash_for_nullify: Field) -> Field {
+            1
         }
 
-        fn compute_note_hash_and_nullifier_without_context(_self: Self) -> (Field, Field) {(1,1)}
+        fn compute_nullifier_without_context(_self: Self) -> Field {
+            1
+        }
 
         fn serialize_content(self) -> [Field; ADDRESS_NOTE_LEN] { [self.address.to_field(), self.owner.to_field(), self.randomness]}
 

noir-projects/aztec-nr/aztec/src/history/note_inclusion.nr

@@ -2,7 +2,7 @@ use dep::protocol_types::merkle_tree::root::root_from_sibling_path;
 use dep::protocol_types::header::Header;
 
 use crate::{
-    note::{utils::compute_note_hash_for_consumption, note_interface::NoteInterface},
+    note::{utils::compute_note_hash_for_nullify, note_interface::NoteInterface},
     oracle::get_membership_witness::get_note_hash_membership_witness
 };
 
@@ -13,7 +13,7 @@ trait ProveNoteInclusion {
 impl ProveNoteInclusion for Header {
     fn prove_note_inclusion<Note, N, M>(self, note: Note) where Note: NoteInterface<N, M> {
         // 1) Compute note_hash
-        let note_hash = compute_note_hash_for_consumption(note);
+        let note_hash = compute_note_hash_for_nullify(note);
 
         // 2) Get the membership witness of the note in the note hash tree
         let witness = get_note_hash_membership_witness(self.global_variables.block_number as u32, note_hash);

noir-projects/aztec-nr/aztec/src/initializer.nr

@@ -1,6 +1,6 @@
 use dep::protocol_types::{
-    address::AztecAddress, hash::{compute_siloed_nullifier, poseidon2_hash_with_separator},
-    constants::GENERATOR_INDEX__CONSTRUCTOR, abis::function_selector::FunctionSelector
+    address::AztecAddress, hash::poseidon2_hash_with_separator, constants::GENERATOR_INDEX__CONSTRUCTOR,
+    abis::function_selector::FunctionSelector
 };
 
 use crate::{

noir-projects/aztec-nr/aztec/src/note/lifecycle.nr

@@ -1,6 +1,7 @@
 use crate::context::{PrivateContext, PublicContext};
 use crate::note::{
-    note_header::NoteHeader, note_interface::NoteInterface, utils::compute_note_hash_for_consumption,
+    note_header::NoteHeader, note_interface::NoteInterface,
+    utils::{compute_note_hash_for_read_request, compute_note_hash_for_nullify_internal},
     note_emission::NoteEmission
 };
 use crate::oracle::notes::{notify_created_note, notify_nullified_note};
@@ -50,14 +51,26 @@ pub fn create_note_hash_from_public<Note, N, M>(
     context.push_note_hash(note_hash);
 }
 
+// Note: This function is currently totally unused.
 pub fn destroy_note<Note, N, M>(
     context: &mut PrivateContext,
     note: Note
 ) where Note: NoteInterface<N, M> {
-    let (note_hash, nullifier) = note.compute_note_hash_and_nullifier(context);
+    let note_hash_for_read_request = compute_note_hash_for_read_request(note);
+
+    destroy_note_unsafe(context, note, note_hash_for_read_request)
+}
+
+pub fn destroy_note_unsafe<Note, N, M>(
+    context: &mut PrivateContext,
+    note: Note,
+    note_hash_for_read_request: Field
+) where Note: NoteInterface<N, M> {
+    let note_hash_for_nullify = compute_note_hash_for_nullify_internal(note, note_hash_for_read_request);
+    let nullifier = note.compute_nullifier(context, note_hash_for_nullify);
 
     let note_hash_counter = note.get_header().note_hash_counter;
-    let note_hash_for_consumption = if (note_hash_counter == 0) {
+    let notification_note_hash = if (note_hash_counter == 0) {
         // Counter is zero, so we're nullifying a settled note and we don't populate the note_hash with real value.
         0
     } else {
@@ -66,11 +79,12 @@ pub fn destroy_note<Note, N, M>(
         // hash with real value to inform the kernel which note we're nullifyng so that it can either squash both
         // the note and the nullifier if it's an inner note hash, or check that the it matches a pending note if it's
         // a siloed note hash.
-        note_hash
+        note_hash_for_nullify
     };
 
     let nullifier_counter = context.side_effect_counter;
-    assert(notify_nullified_note(nullifier, note_hash_for_consumption, nullifier_counter) == 0);
+    assert(notify_nullified_note(nullifier, notification_note_hash, nullifier_counter) == 0);
 
-    context.push_nullifier_for_note_hash(nullifier, note_hash_for_consumption)
+    context.push_nullifier_for_note_hash(nullifier, notification_note_hash)
 }
+

noir-projects/aztec-nr/aztec/src/note/note_getter/mod.nr

@@ -92,22 +92,22 @@ fn check_notes_order<let N: u32>(
 pub fn get_note<Note, let N: u32, let M: u32>(
     context: &mut PrivateContext,
     storage_slot: Field
-) -> Note where Note: NoteInterface<N, M> {
+) -> (Note, Field) where Note: NoteInterface<N, M> {
     let note = get_note_internal(storage_slot);
 
     check_note_header(*context, storage_slot, note);
 
     let note_hash_for_read_request = compute_note_hash_for_read_request(note);
 
     context.push_note_hash_read_request(note_hash_for_read_request);
-    note
+    (note, note_hash_for_read_request)
 }
 
 pub fn get_notes<Note, let N: u32, let M: u32, PREPROCESSOR_ARGS, FILTER_ARGS>(
     context: &mut PrivateContext,
     storage_slot: Field,
     options: NoteGetterOptions<Note, N, M, PREPROCESSOR_ARGS, FILTER_ARGS>
-) -> BoundedVec<Note, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL> where Note: NoteInterface<N, M> + Eq {
+) -> (BoundedVec<Note, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL>, BoundedVec<Field, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL>) where Note: NoteInterface<N, M> + Eq {
     let opt_notes = get_notes_internal(storage_slot, options);
 
     constrain_get_notes_internal(context, storage_slot, opt_notes, options)
@@ -126,7 +126,7 @@ fn constrain_get_notes_internal<Note, let N: u32, let M: u32, PREPROCESSOR_ARGS,
     storage_slot: Field,
     opt_notes: [Option<Note>; MAX_NOTE_HASH_READ_REQUESTS_PER_CALL],
     options: NoteGetterOptions<Note, N, M, PREPROCESSOR_ARGS, FILTER_ARGS>
-) -> BoundedVec<Note, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL> where Note: NoteInterface<N, M> + Eq {
+) -> (BoundedVec<Note, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL>, BoundedVec<Field, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL>) where Note: NoteInterface<N, M> + Eq {
     // The filter is applied first to avoid pushing note read requests for notes we're not interested in. Note that
     // while the filter function can technically mutate the contents of the notes (as opposed to simply removing some),
     // the private kernel will later validate that these note actually exist, so transformations would cause for that
@@ -136,6 +136,7 @@ fn constrain_get_notes_internal<Note, let N: u32, let M: u32, PREPROCESSOR_ARGS,
     let filtered_notes = filter_fn(opt_notes, filter_args);
 
     let notes = crate::utils::collapse(filtered_notes);
+    let mut note_hashes: BoundedVec<Field, MAX_NOTE_HASH_READ_REQUESTS_PER_CALL> = BoundedVec::new();
 
     // We have now collapsed the sparse array of Options into a BoundedVec. This is a more ergonomic type and also
     // results in reduced gate counts when setting a limit value, since we guarantee that the limit is an upper bound
@@ -158,10 +159,11 @@ fn constrain_get_notes_internal<Note, let N: u32, let M: u32, PREPROCESSOR_ARGS,
             // TODO(https://github.com/AztecProtocol/aztec-packages/issues/1410): test to ensure
             // failure if malicious oracle injects 0 nonce here for a "pre-existing" note.
             context.push_note_hash_read_request(note_hash_for_read_request);
+            note_hashes.push(note_hash_for_read_request);
         };
     }
 
-    notes
+    (notes, note_hashes)
 }
 
 unconstrained fn get_note_internal<Note, let N: u32, let M: u32>(storage_slot: Field) -> Note where Note: NoteInterface<N, M> {

noir-projects/aztec-nr/aztec/src/note/note_getter/test.nr

@@ -47,7 +47,7 @@ fn processes_single_note() {
     notes_to_constrain[0] = Option::some(build_valid_note(13));
 
     let options = NoteGetterOptions::new();
-    let returned = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
+    let (returned, _) = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
 
     assert_equivalent_vec_and_array(returned, notes_to_constrain);
     assert_eq(context.note_hash_read_requests.len(), 1);
@@ -63,7 +63,7 @@ fn processes_many_notes() {
     notes_to_constrain[1] = Option::some(build_valid_note(19));
 
     let options = NoteGetterOptions::new();
-    let returned = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
+    let (returned, _) = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
 
     assert_equivalent_vec_and_array(returned, notes_to_constrain);
     assert_eq(context.note_hash_read_requests.len(), 2);
@@ -83,7 +83,7 @@ fn collapses_notes_at_the_beginning_of_the_array() {
     opt_notes[13] = Option::some(build_valid_note(5));
 
     let options = NoteGetterOptions::new();
-    let returned = constrain_get_notes_internal(&mut context, storage_slot, opt_notes, options);
+    let (returned, _) = constrain_get_notes_internal(&mut context, storage_slot, opt_notes, options);
 
     let mut expected = [Option::none(); MAX_NOTE_HASH_READ_REQUESTS_PER_CALL];
     expected[0] = Option::some(build_valid_note(0));
@@ -103,7 +103,7 @@ fn can_return_zero_notes() {
     let opt_notes: [Option<MockNote>; MAX_NOTE_HASH_READ_REQUESTS_PER_CALL] = [Option::none(); MAX_NOTE_HASH_READ_REQUESTS_PER_CALL];
 
     let options = NoteGetterOptions::new();
-    let returned = constrain_get_notes_internal(&mut context, storage_slot, opt_notes, options);
+    let (returned, _) = constrain_get_notes_internal(&mut context, storage_slot, opt_notes, options);
     assert_eq(returned.len(), 0);
 }
 
@@ -145,7 +145,7 @@ fn applies_filter_before_constraining() {
     };
 
     let options = NoteGetterOptions::with_filter(filter_fn, ());
-    let returned = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
+    let (returned, _) = constrain_get_notes_internal(&mut context, storage_slot, notes_to_constrain, options);
 
     // Only the note with value 42 should be returned, and moved to the beginning of the array. The other notes were not
     // constrained, and hence validation did not fail.

noir-projects/aztec-nr/aztec/src/note/note_interface.nr

@@ -4,9 +4,16 @@ use dep::protocol_types::point::Point;
 
 // docs:start:note_interface
 trait NoteInterface<let N: u32, let M: u32> {
-    fn compute_note_hash_and_nullifier(self, context: &mut PrivateContext) -> (Field, Field);
-
-    fn compute_note_hash_and_nullifier_without_context(self) -> (Field, Field);
+    // This function MUST be called with the correct note hash for consumption! It will otherwise silently fail and
+    // compute an incorrect value.
+    // The reason why we receive this as an argument instead of computing it ourselves directly is because the
+    // caller will typically already have computed this note hash, and we can reuse that value to reduce the total
+    // gate count of the circuit.
+    fn compute_nullifier(self, context: &mut PrivateContext, note_hash_for_nullify: Field) -> Field;
+
+    // Unlike compute_nullifier, this function does not take a note hash since it'll only be invoked in unconstrained
+    // contexts, where there is no gate count.
+    fn compute_nullifier_without_context(self) -> Field;
 
     // Autogenerated by the #[aztec(note)] macro unless it is overridden by a custom implementation
     fn serialize_content(self) -> [Field; N];