feat: take an optional owner to create the initialization nullifier

docs/docs/dev_docs/contracts/syntax/storage.md

@@ -257,14 +257,20 @@ As mention, the singleton is initialized to create the first note and value. Her
 
 #include_code initialize /yarn-project/aztec-nr/aztec/src/state_vars/singleton.nr rust
 
-When this function is called, a nullifier of the storage slot is created, preventing this Singleton from being initialized again.
+When this function is called, a nullifier of the storage slot is created, preventing this Singleton from being initialized again. If an `owner` is specified, the nullifier will be hashed with the owner's secret key. It's crucial to provide an owner if the Singleton is associated with an account. Initializing it without an owner may inadvertently reveal important information about the owner's intention.
 
 Unlike public states, which have a default initial value of `0` (or many zeros, in the case of a struct, array or map), a private state (of type `Singleton`, `ImmutableSingleton` or `Set`) does not have a default initial value. The `initialize` method (or `insert`, in the case of a `Set`) must be called.
 
 :::info
 Extend on what happens if you try to use non-initialized state.
 :::
 
+### `is_initialized`
+
+An unconstrained method to check whether the Singleton has been initialized or not.
+
+#include_code is_initialized /yarn-project/aztec-nr/aztec/src/state_vars/singleton.nr rust
+
 ### `replace`
 
 To update the value of a `Singleton`, we can use the `replace` method. The method takes a new note as input, and replaces the current note with the new one. It emits a nullifier for the old value, and inserts the new note into the data tree.
@@ -303,6 +309,8 @@ As part of the initialization of the `Storage` struct, the `Singleton` is create
 
 ### `initialize`
 
+When this function is invoked, it creates a nullifier for the storage slot, ensuring that the ImmutableSingleton cannot be initialized again. If an owner is specified, the nullifier will be hashed with the owner's secret key. It is crucial to provide an owner if the ImmutableSingleton is linked to an account; initializing it without one may inadvertently disclose sensitive information about the owner's intent.
+
 #include_code initialize /yarn-project/aztec-nr/aztec/src/state_vars/immutable_singleton.nr rust
 
 Set the value of an ImmutableSingleton by calling the `initialize` method:
@@ -311,6 +319,12 @@ Set the value of an ImmutableSingleton by calling the `initialize` method:
 
 Once initialized, an ImmutableSingleton's value remains unchangeable. This method can only be called once.
 
+### `is_initialized`
+
+An unconstrained method to check if the ImmutableSingleton has been initialized.
+
+#include_code is_initialized /yarn-project/aztec-nr/aztec/src/state_vars/immutable_singleton.nr rust
+
 ### `get_note`
 
 Similar to the `Singleton`, we can use the `get_note` method to read the value of an ImmutableSingleton.

yarn-project/acir-simulator/src/acvm/oracle/oracle.ts

@@ -123,6 +123,11 @@ export class Oracle {
     return toACVMField(0);
   }
 
+  async checkNullifierExists([innerNullifier]: ACVMField[]): Promise<ACVMField> {
+    const exists = await this.typedOracle.checkNullifierExists(fromACVMField(innerNullifier));
+    return toACVMField(exists);
+  }
+
   async getL1ToL2Message([msgKey]: ACVMField[]): Promise<ACVMField[]> {
     const { root, ...message } = await this.typedOracle.getL1ToL2Message(fromACVMField(msgKey));
     return toAcvmL1ToL2MessageLoadOracleInputs(message, root);

yarn-project/acir-simulator/src/acvm/oracle/typed_oracle.ts

@@ -105,6 +105,10 @@ export abstract class TypedOracle {
     throw new Error('Not available.');
   }
 
+  checkNullifierExists(_innerNullifier: Fr): Promise<boolean> {
+    throw new Error('Not available.');
+  }
+
   getL1ToL2Message(_msgKey: Fr): Promise<L1ToL2MessageOracleReturnData> {
     throw new Error('Not available.');
   }

yarn-project/acir-simulator/src/client/db_oracle.ts

@@ -77,6 +77,13 @@ export interface DBOracle extends CommitmentsDB {
    */
   getPortalContractAddress(contractAddress: AztecAddress): Promise<EthAddress>;
 
+  /**
+   * Gets the index of a nullifier in the nullifier tree.
+   * @param nullifier - The nullifier.
+   * @returns - The index of the nullifier. Undefined if it does not exist in the tree.
+   */
+  getNullifierIndex(nullifier: Fr): Promise<bigint | undefined>;
+
   /**
    * Retrieve the databases view of the Historic Block Data object.
    * This structure is fed into the circuits simulator and is used to prove against certain historic roots.

yarn-project/acir-simulator/src/client/view_data_oracle.ts

@@ -1,4 +1,5 @@
-import { HistoricBlockData, PublicKey } from '@aztec/circuits.js';
+import { CircuitsWasm, HistoricBlockData, PublicKey } from '@aztec/circuits.js';
+import { siloNullifier } from '@aztec/circuits.js/abis';
 import { AztecAddress } from '@aztec/foundation/aztec-address';
 import { Fr } from '@aztec/foundation/fields';
 import { createDebugLogger } from '@aztec/foundation/log';
@@ -99,6 +100,18 @@ export class ViewDataOracle extends TypedOracle {
     });
   }
 
+  /**
+   * Check if a nullifier exists in the nullifier tree.
+   * @param innerNullifier - The inner nullifier.
+   * @returns A boolean indicating whether the nullifier exists in the tree or not.
+   */
+  public async checkNullifierExists(innerNullifier: Fr) {
+    const wasm = await CircuitsWasm.get();
+    const nullifier = siloNullifier(wasm, this.contractAddress, innerNullifier!);
+    const index = await this.db.getNullifierIndex(nullifier);
+    return index !== undefined;
+  }
+
   /**
    * Fetches the a message from the db, given its key.
    * @param msgKey - A buffer representing the message key.

yarn-project/aztec-nr/aztec/src/oracle/notes.nr

@@ -98,7 +98,11 @@ unconstrained fn get_notes<Note, N, M, S, NS>(
     placeholder_opt_notes
 }
 
-unconstrained fn is_nullifier_emitted(nullifier: Field) -> bool {
-    // TODO
-    nullifier == 0
+#[oracle(checkNullifierExists)]
+fn check_nullifier_exists_oracle(
+    _inner_nullifier: Field,
+) -> Field {}
+
+unconstrained fn check_nullifier_exists(inner_nullifier: Field) -> bool {
+    check_nullifier_exists_oracle(inner_nullifier) == 1
 }

yarn-project/aztec-nr/aztec/src/state_vars/immutable_singleton.nr

@@ -1,20 +1,21 @@
-use crate::constants_gen::{EMPTY_NULLIFIED_COMMITMENT, GENERATOR_INDEX__INITIALISATION_NULLIFIER};
+use dep::std::option::Option;
+use crate::constants_gen::EMPTY_NULLIFIED_COMMITMENT;
 use crate::context::{PrivateContext, Context};
 use crate::note::{
     lifecycle::create_note,
     note_getter::{get_note, view_notes},
     note_interface::NoteInterface,
     note_viewer_options::NoteViewerOptions,
 };
-use crate::oracle;
-use dep::std::hash::pedersen_with_separator;
-use dep::std::option::Option;
+use crate::oracle::notes::check_nullifier_exists;
+use crate::state_vars::singleton::compute_singleton_initialization_nullifier;
 
 // docs:start:struct
 struct ImmutableSingleton<Note, N> {
-    context: Context,
+    context: Option<&mut PrivateContext>,
     storage_slot: Field,
     note_interface: NoteInterface<Note, N>,
+    compute_initialization_nullifier: fn (Field, Option<Field>) -> Field,
 }
 // docs:end:struct
 
@@ -27,46 +28,45 @@ impl<Note, N> ImmutableSingleton<Note, N> {
     ) -> Self {
         assert(storage_slot != 0, "Storage slot 0 not allowed. Storage slots must start from 1.");
         ImmutableSingleton {
-            context,
+            context: context.private,
             storage_slot,
             note_interface,
+            compute_initialization_nullifier: compute_singleton_initialization_nullifier,
         }
     }
     // docs:end:new
 
-    unconstrained fn is_initialized(self) -> bool {
-        let nullifier = self.compute_initialisation_nullifier();
-        oracle::notes::is_nullifier_emitted(nullifier)
+    // docs:start:is_initialized
+    unconstrained fn is_initialized(self, owner: Option<Field>) -> bool {
+        let compute_initialization_nullifier = self.compute_initialization_nullifier;
+        let nullifier = compute_initialization_nullifier(self.storage_slot, owner);
+        check_nullifier_exists(nullifier)
     }
+    // docs:end:is_initialized
 
     // docs:start:initialize
-    fn initialize(self, note: &mut Note) {
+    fn initialize(self, note: &mut Note, owner: Option<Field>) {
+        let context = self.context.unwrap_unchecked();
+
         // Nullify the storage slot.
-        let nullifier = self.compute_initialisation_nullifier();
-        self.context.private
-            .unwrap()
-            .push_new_nullifier(nullifier, EMPTY_NULLIFIED_COMMITMENT);
+        let compute_initialization_nullifier = self.compute_initialization_nullifier;
+        let nullifier = compute_initialization_nullifier(self.storage_slot, owner);
+        context.push_new_nullifier(nullifier, EMPTY_NULLIFIED_COMMITMENT);
 
         create_note(
-            self.context.private.unwrap(),
+            context,
             self.storage_slot,
             note,
             self.note_interface,
         );
     }
     // docs:end:initialize
 
-    fn compute_initialisation_nullifier(self) -> Field {
-        pedersen_with_separator(
-            [self.storage_slot],
-            GENERATOR_INDEX__INITIALISATION_NULLIFIER,
-        )[0]
-    }
-
     // docs:start:get_note
     fn get_note(self) -> Note {
+        let context = self.context.unwrap_unchecked();
         let storage_slot = self.storage_slot;
-        get_note(self.context.private.unwrap(), storage_slot, self.note_interface)
+        get_note(context, storage_slot, self.note_interface)
     }
     // docs:end:get_note
 

yarn-project/aztec-nr/aztec/src/state_vars/singleton.nr

@@ -1,3 +1,4 @@
+use dep::std::option::Option;
 use crate::constants_gen::{EMPTY_NULLIFIED_COMMITMENT, GENERATOR_INDEX__INITIALISATION_NULLIFIER};
 use crate::context::{PrivateContext, PublicContext, Context};
 use crate::note::{
@@ -6,15 +7,33 @@ use crate::note::{
     note_interface::NoteInterface,
     note_viewer_options::NoteViewerOptions,
 };
-use crate::oracle;
+use crate::oracle::{
+    get_secret_key::get_secret_key,
+    notes::check_nullifier_exists,
+};
 use dep::std::hash::pedersen_with_separator;
-use dep::std::option::Option;
+
+fn compute_singleton_initialization_nullifier(storage_slot: Field, owner: Option<Field>) -> Field {
+    if owner.is_some() {
+        let secret = get_secret_key(owner.unwrap_unchecked());
+        pedersen_with_separator(
+            [storage_slot, secret.low, secret.high],
+            GENERATOR_INDEX__INITIALISATION_NULLIFIER,
+        )[0]
+    } else {
+        pedersen_with_separator(
+            [storage_slot],
+            GENERATOR_INDEX__INITIALISATION_NULLIFIER,
+        )[0]
+    }
+}
 
 // docs:start:struct
 struct Singleton<Note, N> {
     context: Option<&mut PrivateContext>,
     storage_slot: Field,
     note_interface: NoteInterface<Note, N>,
+    compute_initialization_nullifier: fn (Field, Option<Field>) -> Field,
 }
 // docs:end:struct
 
@@ -30,36 +49,35 @@ impl<Note, N> Singleton<Note, N> {
             context: context.private,
             storage_slot,
             note_interface,
+            compute_initialization_nullifier: compute_singleton_initialization_nullifier,
         }
     }
     // docs:end:new
 
-    unconstrained fn is_initialized(self) -> bool {
-        let nullifier = self.compute_initialisation_nullifier();
-        oracle::notes::is_nullifier_emitted(nullifier)
+    // docs:start:is_initialized
+    unconstrained fn is_initialized(self, owner: Option<Field>) -> bool {
+        let compute_initialization_nullifier = self.compute_initialization_nullifier;
+        let nullifier = compute_initialization_nullifier(self.storage_slot, owner);
+        check_nullifier_exists(nullifier)
     }
+    // docs:end:is_initialized
 
     // docs:start:initialize
-    fn initialize(self, note: &mut Note) {
-        let context = self.context.unwrap();
+    fn initialize(self, note: &mut Note, owner: Option<Field>) {
+        let context = self.context.unwrap_unchecked();
+
         // Nullify the storage slot.
-        let nullifier = self.compute_initialisation_nullifier();
+        let compute_initialization_nullifier = self.compute_initialization_nullifier;
+        let nullifier = compute_initialization_nullifier(self.storage_slot, owner);
         context.push_new_nullifier(nullifier, EMPTY_NULLIFIED_COMMITMENT);
 
         create_note(context, self.storage_slot, note, self.note_interface);
     }
     // docs:end:initialize
 
-    fn compute_initialisation_nullifier(self) -> Field {
-        pedersen_with_separator(
-            [self.storage_slot],
-            GENERATOR_INDEX__INITIALISATION_NULLIFIER,
-        )[0]
-    }
-
     // docs:start:replace
     fn replace(self, new_note: &mut Note) {
-        let context = self.context.unwrap();
+        let context = self.context.unwrap_unchecked();
         let prev_note = get_note(context, self.storage_slot, self.note_interface);
 
         // Nullify previous note.
@@ -72,7 +90,7 @@ impl<Note, N> Singleton<Note, N> {
 
     // docs:start:get_note
     fn get_note(self) -> Note {
-        let context = self.context.unwrap();
+        let context = self.context.unwrap_unchecked();
         let mut note = get_note(context, self.storage_slot, self.note_interface);
 
         // Nullify current note to make sure it's reading the latest note.