chore: do not pass redundant txNullifier when computing notes (AztecP…

…rotocol#3943)

When computing note daos, we were previously passing around a
`txNullifier` and `txHash`. That is redundant, as one is an encoding of
the other.

yarn-project/pxe/src/database/deferred_note_dao.test.ts

@@ -9,7 +9,6 @@ export const randomDeferredNoteDao = ({
   contractAddress = AztecAddress.random(),
   txHash = randomTxHash(),
   storageSlot = Fr.random(),
-  txNullifier = Fr.random(),
   newCommitments = [Fr.random(), Fr.random()],
   dataStartIndexForTx = Math.floor(Math.random() * 100),
 }: Partial<DeferredNoteDao> = {}) => {
@@ -19,7 +18,6 @@ export const randomDeferredNoteDao = ({
     contractAddress,
     storageSlot,
     txHash,
-    txNullifier,
     newCommitments,
     dataStartIndexForTx,
   );

yarn-project/pxe/src/database/deferred_note_dao.ts

@@ -17,10 +17,8 @@ export class DeferredNoteDao {
     public contractAddress: AztecAddress,
     /** The specific storage location of the note on the contract. */
     public storageSlot: Fr,
-    /** The hash of the tx the note was created in. */
+    /** The hash of the tx the note was created in. Equal to the first nullifier */
     public txHash: TxHash,
-    /** The first nullifier emitted by the transaction */
-    public txNullifier: Fr,
     /** New commitments in this transaction, one of which belongs to this note */
     public newCommitments: Fr[],
     /** The next available leaf index for the note hash tree for this transaction */
@@ -34,7 +32,6 @@ export class DeferredNoteDao {
       this.contractAddress.toBuffer(),
       this.storageSlot.toBuffer(),
       this.txHash.toBuffer(),
-      this.txNullifier.toBuffer(),
       new Vector(this.newCommitments),
       this.dataStartIndexForTx,
     );
@@ -47,7 +44,6 @@ export class DeferredNoteDao {
       reader.readObject(AztecAddress),
       reader.readObject(Fr),
       reader.readObject(TxHash),
-      reader.readObject(Fr),
       reader.readVector(Fr),
       reader.readNumber(),
     );

yarn-project/pxe/src/note_processor/note_processor.ts

@@ -1,5 +1,5 @@
 import { ContractNotFoundError } from '@aztec/acir-simulator';
-import { MAX_NEW_COMMITMENTS_PER_TX, MAX_NEW_NULLIFIERS_PER_TX, PublicKey } from '@aztec/circuits.js';
+import { MAX_NEW_COMMITMENTS_PER_TX, PublicKey } from '@aztec/circuits.js';
 import { Grumpkin } from '@aztec/circuits.js/barretenberg';
 import { Fr } from '@aztec/foundation/fields';
 import { createDebugLogger } from '@aztec/foundation/log';
@@ -121,10 +121,6 @@ export class NoteProcessor {
           indexOfTxInABlock * MAX_NEW_COMMITMENTS_PER_TX,
           (indexOfTxInABlock + 1) * MAX_NEW_COMMITMENTS_PER_TX,
         );
-        const newNullifiers = block.newNullifiers.slice(
-          indexOfTxInABlock * MAX_NEW_NULLIFIERS_PER_TX,
-          (indexOfTxInABlock + 1) * MAX_NEW_NULLIFIERS_PER_TX,
-        );
         // Note: Each tx generates a `TxL2Logs` object and for this reason we can rely on its index corresponding
         //       to the index of a tx in a block.
         const txFunctionLogs = txLogs[indexOfTxInABlock].functionLogs;
@@ -136,14 +132,12 @@ export class NoteProcessor {
             if (payload) {
               // We have successfully decrypted the data.
               const txHash = blockContext.getTxHash(indexOfTxInABlock);
-              const txNullifier = newNullifiers[0];
               try {
                 const noteDao = await produceNoteDao(
                   this.simulator,
                   this.publicKey,
                   payload,
                   txHash,
-                  txNullifier,
                   newCommitments,
                   dataStartIndexForTx,
                   excludedIndices,
@@ -160,7 +154,6 @@ export class NoteProcessor {
                     payload.contractAddress,
                     payload.storageSlot,
                     txHash,
-                    txNullifier,
                     newCommitments,
                     dataStartIndexForTx,
                   );
@@ -254,8 +247,7 @@ export class NoteProcessor {
     const excludedIndices: Set<number> = new Set();
     const noteDaos: NoteDao[] = [];
     for (const deferredNote of deferredNoteDaos) {
-      const { note, contractAddress, storageSlot, txHash, txNullifier, newCommitments, dataStartIndexForTx } =
-        deferredNote;
+      const { note, contractAddress, storageSlot, txHash, newCommitments, dataStartIndexForTx } = deferredNote;
       const payload = new L1NotePayload(note, contractAddress, storageSlot);
 
       try {
@@ -264,7 +256,6 @@ export class NoteProcessor {
           this.publicKey,
           payload,
           txHash,
-          txNullifier,
           newCommitments,
           dataStartIndexForTx,
           excludedIndices,

yarn-project/pxe/src/note_processor/produce_note_dao.ts

@@ -13,8 +13,7 @@ import { NoteDao } from '../database/note_dao.js';
  *
  * @param publicKey - The public counterpart to the private key to be used in note decryption.
  * @param payload - An instance of l1NotePayload.
- * @param txHash - The hash of the transaction that created the note.
- * @param txNullifier - The first nullifier emitted by the transaction.
+ * @param txHash - The hash of the transaction that created the note. Equivalent to the first nullifier of the transaction.
  * @param newCommitments - New commitments in this transaction, one of which belongs to this note.
  * @param dataStartIndexForTx - The next available leaf index for the note hash tree for this transaction.
  * @param excludedIndices - Indices that have been assigned a note in the same tx. Notes in a tx can have the same l1NotePayload, we need to find a different index for each replicate.
@@ -26,15 +25,14 @@ export async function produceNoteDao(
   publicKey: PublicKey,
   payload: L1NotePayload,
   txHash: TxHash,
-  txNullifier: Fr,
   newCommitments: Fr[],
   dataStartIndexForTx: number,
   excludedIndices: Set<number>,
 ): Promise<NoteDao> {
   const { commitmentIndex, nonce, innerNoteHash, siloedNullifier } = await findNoteIndexAndNullifier(
     simulator,
     newCommitments,
-    txNullifier,
+    txHash,
     payload,
     excludedIndices,
   );
@@ -61,7 +59,7 @@ export async function produceNoteDao(
  * contract address, and the note associated with the l1NotePayload.
  * This method assists in identifying spent commitments in the private state.
  * @param commitments - Commitments in the tx. One of them should be the note's commitment.
- * @param firstNullifier - First nullifier in the tx.
+ * @param txHash - First nullifier in the tx.
  * @param l1NotePayload - An instance of l1NotePayload.
  * @param excludedIndices - Indices that have been assigned a note in the same tx. Notes in a tx can have the same
  * l1NotePayload. We need to find a different index for each replicate.
@@ -71,7 +69,7 @@ export async function produceNoteDao(
 async function findNoteIndexAndNullifier(
   simulator: AcirSimulator,
   commitments: Fr[],
-  firstNullifier: Fr,
+  txHash: TxHash,
   { contractAddress, storageSlot, note }: L1NotePayload,
   excludedIndices: Set<number>,
 ) {
@@ -81,6 +79,8 @@ async function findNoteIndexAndNullifier(
   let siloedNoteHash: Fr | undefined;
   let uniqueSiloedNoteHash: Fr | undefined;
   let innerNullifier: Fr | undefined;
+  const firstNullifier = Fr.fromBuffer(txHash.toBuffer());
+
   for (; commitmentIndex < commitments.length; ++commitmentIndex) {
     if (excludedIndices.has(commitmentIndex)) {
       continue;

yarn-project/types/src/l2_block.ts

@@ -25,6 +25,7 @@ import { L2Tx } from './l2_tx.js';
 import { LogType, TxL2Logs } from './logs/index.js';
 import { L2BlockL2Logs } from './logs/l2_block_l2_logs.js';
 import { PublicDataWrite } from './public_data_write.js';
+import { TxHash } from './tx/tx_hash.js';
 
 /**
  * The data that makes up the rollup proof, with encoder decoder functions.
@@ -620,13 +621,7 @@ export class L2Block {
    * @returns The tx.
    */
   getTx(txIndex: number) {
-    if (txIndex >= this.numberOfTxs) {
-      throw new Error(
-        `Failed to get tx ${txIndex}. Block ${this.header.globalVariables.blockNumber.toBigInt()} only has ${
-          this.numberOfTxs
-        } txs.`,
-      );
-    }
+    this.assertIndexInRange(txIndex);
 
     const newCommitments = this.newCommitments
       .slice(MAX_NEW_COMMITMENTS_PER_TX * txIndex, MAX_NEW_COMMITMENTS_PER_TX * (txIndex + 1))
@@ -659,6 +654,19 @@ export class L2Block {
     );
   }
 
+  /**
+   * A lightweight method to get the tx hash of a tx in the block.
+   * @param txIndex - the index of the tx in the block
+   * @returns a hash of the tx, which is the first nullifier in the tx
+   */
+  getTxHash(txIndex: number): TxHash {
+    this.assertIndexInRange(txIndex);
+
+    const firstNullifier = this.newNullifiers[txIndex * MAX_NEW_NULLIFIERS_PER_TX];
+
+    return new TxHash(firstNullifier.toBuffer());
+  }
+
   /**
    * Get all the transaction in an L2 block.
    * @returns The tx.
@@ -690,6 +698,16 @@ export class L2Block {
     };
   }
 
+  assertIndexInRange(txIndex: number) {
+    if (txIndex < 0 || txIndex >= this.numberOfTxs) {
+      throw new IndexOutOfRangeError({
+        txIndex,
+        numberOfTxs: this.numberOfTxs,
+        blockNumber: this.number,
+      });
+    }
+  }
+
   // /**
   //  * Inspect for debugging purposes..
   //  * @param maxBufferSize - The number of bytes to be extracted from buffer.
@@ -765,3 +783,29 @@ export class L2Block {
     return kernelPublicInputsLogsHash;
   }
 }
+
+/**
+ * Custom error class for when a requested tx index is out of range.
+ */
+export class IndexOutOfRangeError extends Error {
+  constructor({
+    txIndex,
+    numberOfTxs,
+    blockNumber,
+  }: {
+    /**
+     * The requested index of the tx in the block.
+     */
+    txIndex: number;
+    /**
+     * The number of txs in the block.
+     */
+    numberOfTxs: number;
+    /**
+     * The number of the block.
+     */
+    blockNumber: number;
+  }) {
+    super(`IndexOutOfRangeError: Failed to get tx at index ${txIndex}. Block ${blockNumber} has ${numberOfTxs} txs.`);
+  }
+}

yarn-project/types/src/l2_block_context.ts

@@ -20,7 +20,7 @@ export class L2BlockContext {
    * @returns The tx's hash.
    */
   public getTxHash(txIndex: number): TxHash {
-    return this.txHashes ? this.txHashes[txIndex] : this.block.getTx(txIndex).txHash;
+    return this.txHashes ? this.txHashes[txIndex] : this.block.getTxHash(txIndex);
   }
 
   /**