diff --git a/yarn-project/accounts/src/defaults/account_entrypoint.ts b/yarn-project/accounts/src/defaults/account_entrypoint.ts
index 67b62181dfd5..f64db020b70e 100644
--- a/yarn-project/accounts/src/defaults/account_entrypoint.ts
+++ b/yarn-project/accounts/src/defaults/account_entrypoint.ts
@@ -1,6 +1,6 @@
 import { AuthWitnessProvider, EntrypointInterface, FeeOptions } from '@aztec/aztec.js/account';
 import { FunctionCall, PackedArguments, TxExecutionRequest } from '@aztec/circuit-types';
-import { AztecAddress, Fr, FunctionData, GeneratorIndex, TxContext } from '@aztec/circuits.js';
+import { AztecAddress, FunctionData, GeneratorIndex, TxContext } from '@aztec/circuits.js';
 import { FunctionAbi, encodeArguments } from '@aztec/foundation/abi';
 
 import { DEFAULT_CHAIN_ID, DEFAULT_VERSION } from './constants.js';
@@ -25,12 +25,8 @@ export class DefaultAccountEntrypoint implements EntrypointInterface {
     const abi = this.getEntrypointAbi();
     const entrypointPackedArgs = PackedArguments.fromArgs(encodeArguments(abi, [appPayload, feePayload]));
 
-    const appAuthWitness = await this.auth.createAuthWitness(
-      Fr.fromBuffer(hashPayload(appPayload, GeneratorIndex.SIGNATURE_PAYLOAD)),
-    );
-    const feeAuthWitness = await this.auth.createAuthWitness(
-      Fr.fromBuffer(hashPayload(feePayload, GeneratorIndex.FEE_PAYLOAD)),
-    );
+    const appAuthWitness = await this.auth.createAuthWitness(hashPayload(appPayload, GeneratorIndex.SIGNATURE_PAYLOAD));
+    const feeAuthWitness = await this.auth.createAuthWitness(hashPayload(feePayload, GeneratorIndex.FEE_PAYLOAD));
 
     const txRequest = TxExecutionRequest.from({
       argsHash: entrypointPackedArgs.hash,
diff --git a/yarn-project/aztec.js/src/utils/cheat_codes.ts b/yarn-project/aztec.js/src/utils/cheat_codes.ts
index 02ce3e565493..b22aa828bee5 100644
--- a/yarn-project/aztec.js/src/utils/cheat_codes.ts
+++ b/yarn-project/aztec.js/src/utils/cheat_codes.ts
@@ -246,7 +246,7 @@ export class AztecCheatCodes {
   public computeSlotInMap(baseSlot: Fr | bigint, key: Fr | bigint | AztecAddress): Fr {
     // Based on `at` function in
     // aztec3-packages/aztec-nr/aztec/src/state_vars/map.nr
-    return Fr.fromBuffer(pedersenHash([new Fr(baseSlot), new Fr(key)].map(f => f.toBuffer())));
+    return pedersenHash([new Fr(baseSlot), new Fr(key)].map(f => f.toBuffer()));
   }
 
   /**
diff --git a/yarn-project/end-to-end/src/e2e_blacklist_token_contract.test.ts b/yarn-project/end-to-end/src/e2e_blacklist_token_contract.test.ts
index db68e95f98df..5787e13e7b15 100644
--- a/yarn-project/end-to-end/src/e2e_blacklist_token_contract.test.ts
+++ b/yarn-project/end-to-end/src/e2e_blacklist_token_contract.test.ts
@@ -813,7 +813,7 @@ describe('e2e_blacklist_token_contract', () => {
           );
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${messageHash.toString('hex')}`,
+            `Unknown auth witness for message hash 0x${messageHash.toString()}`,
           );
         });
 
@@ -840,7 +840,7 @@ describe('e2e_blacklist_token_contract', () => {
           );
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+            `Unknown auth witness for message hash 0x${expectedMessageHash.toString()}`,
           );
           expect(await asset.methods.balance_of_private(accounts[0].address).view()).toEqual(balance0);
         });
@@ -1147,7 +1147,7 @@ describe('e2e_blacklist_token_contract', () => {
         );
 
         await expect(action.simulate()).rejects.toThrowError(
-          `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+          `Unknown auth witness for message hash 0x${expectedMessageHash.toString()}`,
         );
       });
 
@@ -1386,7 +1386,7 @@ describe('e2e_blacklist_token_contract', () => {
           const messageHash = computeAuthWitMessageHash(accounts[1].address, action.request());
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${messageHash.toString('hex')}`,
+            `Unknown auth witness for message hash 0x${messageHash.toString()}`,
           );
         });
 
@@ -1408,7 +1408,7 @@ describe('e2e_blacklist_token_contract', () => {
           await wallets[2].addAuthWitness(witness);
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+            `Unknown auth witness for message hash 0x${expectedMessageHash.toString()}`,
           );
         });
 
diff --git a/yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts b/yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts
index 9e5932e00d4e..8d5a9418c92b 100644
--- a/yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts
+++ b/yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts
@@ -203,7 +203,7 @@ describe('e2e_cross_chain_messaging', () => {
         .withWallet(user1Wallet)
         .methods.exit_to_l1_private(l2Token.address, ethAccount, withdrawAmount, EthAddress.ZERO, nonce)
         .simulate(),
-    ).rejects.toThrowError(`Unknown auth witness for message hash 0x${expectedBurnMessageHash.toString('hex')}`);
+    ).rejects.toThrowError(`Unknown auth witness for message hash 0x${expectedBurnMessageHash.toString()}`);
   }, 120_000);
 
   it("Can't claim funds publicly if they were deposited privately", async () => {
diff --git a/yarn-project/end-to-end/src/e2e_lending_contract.test.ts b/yarn-project/end-to-end/src/e2e_lending_contract.test.ts
index a33526523edf..10c6cbae525c 100644
--- a/yarn-project/end-to-end/src/e2e_lending_contract.test.ts
+++ b/yarn-project/end-to-end/src/e2e_lending_contract.test.ts
@@ -172,7 +172,7 @@ describe('e2e_lending_contract', () => {
           .request(),
       );
 
-      await wallet.createAuthWitness(Fr.fromBuffer(messageHash));
+      await wallet.createAuthWitness(messageHash);
       await lendingSim.progressTime(TIME_JUMP);
       lendingSim.depositPrivate(lendingAccount.address, lendingAccount.key(), depositAmount);
 
@@ -205,7 +205,7 @@ describe('e2e_lending_contract', () => {
           .unshield(lendingAccount.address, lendingContract.address, depositAmount, nonce)
           .request(),
       );
-      await wallet.createAuthWitness(Fr.fromBuffer(messageHash));
+      await wallet.createAuthWitness(messageHash);
 
       await lendingSim.progressTime(TIME_JUMP);
       lendingSim.depositPrivate(lendingAccount.address, lendingAccount.address.toField(), depositAmount);
@@ -303,7 +303,7 @@ describe('e2e_lending_contract', () => {
         lendingContract.address,
         stableCoin.methods.burn(lendingAccount.address, repayAmount, nonce).request(),
       );
-      await wallet.createAuthWitness(Fr.fromBuffer(messageHash));
+      await wallet.createAuthWitness(messageHash);
 
       await lendingSim.progressTime(TIME_JUMP);
       lendingSim.repayPrivate(lendingAccount.address, lendingAccount.key(), repayAmount);
@@ -329,7 +329,7 @@ describe('e2e_lending_contract', () => {
         lendingContract.address,
         stableCoin.methods.burn(lendingAccount.address, repayAmount, nonce).request(),
       );
-      await wallet.createAuthWitness(Fr.fromBuffer(messageHash));
+      await wallet.createAuthWitness(messageHash);
 
       await lendingSim.progressTime(TIME_JUMP);
       lendingSim.repayPrivate(lendingAccount.address, lendingAccount.address.toField(), repayAmount);
diff --git a/yarn-project/end-to-end/src/e2e_token_contract.test.ts b/yarn-project/end-to-end/src/e2e_token_contract.test.ts
index 42792edbe753..bb667a391791 100644
--- a/yarn-project/end-to-end/src/e2e_token_contract.test.ts
+++ b/yarn-project/end-to-end/src/e2e_token_contract.test.ts
@@ -614,7 +614,7 @@ describe('e2e_token_contract', () => {
           const messageHash = computeAuthWitMessageHash(accounts[1].address, action.request());
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${messageHash.toString('hex')}`,
+            `Unknown auth witness for message hash ${messageHash.toString()}`,
           );
         });
 
@@ -635,7 +635,7 @@ describe('e2e_token_contract', () => {
           await wallets[2].addAuthWitness(witness);
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+            `Unknown auth witness for message hash ${expectedMessageHash.toString()}`,
           );
           expect(await asset.methods.balance_of_private(accounts[0].address).view()).toEqual(balance0);
         });
@@ -874,7 +874,7 @@ describe('e2e_token_contract', () => {
         await wallets[2].addAuthWitness(witness);
 
         await expect(action.simulate()).rejects.toThrowError(
-          `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+          `Unknown auth witness for message hash ${expectedMessageHash.toString()}`,
         );
       });
     });
@@ -1062,7 +1062,7 @@ describe('e2e_token_contract', () => {
           const messageHash = computeAuthWitMessageHash(accounts[1].address, action.request());
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${messageHash.toString('hex')}`,
+            `Unknown auth witness for message hash ${messageHash.toString()}`,
           );
         });
 
@@ -1081,7 +1081,7 @@ describe('e2e_token_contract', () => {
           await wallets[2].addAuthWitness(witness);
 
           await expect(action.simulate()).rejects.toThrowError(
-            `Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`,
+            `Unknown auth witness for message hash ${expectedMessageHash.toString()}`,
           );
         });
       });
diff --git a/yarn-project/end-to-end/src/shared/uniswap_l1_l2.ts b/yarn-project/end-to-end/src/shared/uniswap_l1_l2.ts
index cbf7df990026..9a5669165d47 100644
--- a/yarn-project/end-to-end/src/shared/uniswap_l1_l2.ts
+++ b/yarn-project/end-to-end/src/shared/uniswap_l1_l2.ts
@@ -206,7 +206,7 @@ export const uniswapL1L2TestSuite = (
           .unshield(ownerAddress, uniswapL2Contract.address, wethAmountToBridge, nonceForWETHUnshieldApproval)
           .request(),
       );
-      await ownerWallet.createAuthWitness(Fr.fromBuffer(unshieldToUniswapMessageHash));
+      await ownerWallet.createAuthWitness(unshieldToUniswapMessageHash);
 
       // 4. Swap on L1 - sends L2 to L1 message to withdraw WETH to L1 and another message to swap assets.
       logger('Withdrawing weth to L1 and sending message to swap to dai');
@@ -475,7 +475,7 @@ export const uniswapL1L2TestSuite = (
             ownerEthAddress,
           )
           .simulate(),
-      ).rejects.toThrowError(`Unknown auth witness for message hash 0x${expectedMessageHash.toString('hex')}`);
+      ).rejects.toThrowError(`Unknown auth witness for message hash ${expectedMessageHash.toString()}`);
     });
 
     it("can't swap if user passes a token different to what the bridge tracks", async () => {
@@ -494,7 +494,7 @@ export const uniswapL1L2TestSuite = (
           .unshield(ownerAddress, uniswapL2Contract.address, wethAmountToBridge, nonceForWETHUnshieldApproval)
           .request(),
       );
-      await ownerWallet.createAuthWitness(Fr.fromBuffer(unshieldToUniswapMessageHash));
+      await ownerWallet.createAuthWitness(unshieldToUniswapMessageHash);
 
       // 3. Swap but send the wrong token address
       logger('Swap but send the wrong token address');
@@ -644,7 +644,7 @@ export const uniswapL1L2TestSuite = (
           .unshield(ownerAddress, uniswapL2Contract.address, wethAmountToBridge, nonceForWETHUnshieldApproval)
           .request(),
       );
-      await ownerWallet.createAuthWitness(Fr.fromBuffer(unshieldToUniswapMessageHash));
+      await ownerWallet.createAuthWitness(unshieldToUniswapMessageHash);
       const wethL2BalanceBeforeSwap = await wethCrossChainHarness.getL2PrivateBalanceOf(ownerAddress);
 
       // Swap
diff --git a/yarn-project/end-to-end/src/simulators/lending_simulator.ts b/yarn-project/end-to-end/src/simulators/lending_simulator.ts
index dcc91fa28a12..2a0da49ed1d0 100644
--- a/yarn-project/end-to-end/src/simulators/lending_simulator.ts
+++ b/yarn-project/end-to-end/src/simulators/lending_simulator.ts
@@ -24,7 +24,7 @@ export class LendingAccount {
    * @returns Key in public space
    */
   public key() {
-    return Fr.fromBuffer(pedersenHash([this.address, this.secret].map(f => f.toBuffer())));
+    return pedersenHash([this.address, this.secret].map(f => f.toBuffer()));
   }
 }
 
diff --git a/yarn-project/foundation/src/crypto/poseidon/index.ts b/yarn-project/foundation/src/crypto/poseidon/index.ts
index 7cc44a95b5e6..8f77b5802115 100644
--- a/yarn-project/foundation/src/crypto/poseidon/index.ts
+++ b/yarn-project/foundation/src/crypto/poseidon/index.ts
@@ -1,13 +1,17 @@
-import { BarretenbergSync, Fr } from '@aztec/bb.js';
+import { BarretenbergSync, Fr as FrBarretenberg } from '@aztec/bb.js';
+
+import { Fr } from '../../fields/fields.js';
 
 /**
  * Create a poseidon hash (field) from an array of input fields.
  * Left pads any inputs less than 32 bytes.
  */
-export function poseidonHash(input: Buffer[]): Buffer {
-  return Buffer.from(
-    BarretenbergSync.getSingleton()
-      .poseidonHash(input.map(i => new Fr(i)))
-      .toBuffer(),
+export function poseidonHash(input: Buffer[]): Fr {
+  return Fr.fromBuffer(
+    Buffer.from(
+      BarretenbergSync.getSingleton()
+        .poseidonHash(input.map(i => new FrBarretenberg(i)))
+        .toBuffer(),
+    ),
   );
 }
diff --git a/yarn-project/merkle-tree/src/pedersen.ts b/yarn-project/merkle-tree/src/pedersen.ts
index 2cc990049702..b4a749e5a8a8 100644
--- a/yarn-project/merkle-tree/src/pedersen.ts
+++ b/yarn-project/merkle-tree/src/pedersen.ts
@@ -12,7 +12,7 @@ export class Pedersen implements Hasher {
    * purposes.
    */
   public hash(lhs: Uint8Array, rhs: Uint8Array): Buffer {
-    return pedersenHash([Buffer.from(lhs), Buffer.from(rhs)]);
+    return pedersenHash([Buffer.from(lhs), Buffer.from(rhs)]).toBuffer();
   }
 
   /*
@@ -20,6 +20,6 @@ export class Pedersen implements Hasher {
    * purposes.
    */
   public hashInputs(inputs: Buffer[]): Buffer {
-    return pedersenHash(inputs);
+    return pedersenHash(inputs).toBuffer();
   }
 }
diff --git a/yarn-project/pxe/src/note_processor/note_processor.test.ts b/yarn-project/pxe/src/note_processor/note_processor.test.ts
index 3770584959c4..6c66111c2b08 100644
--- a/yarn-project/pxe/src/note_processor/note_processor.test.ts
+++ b/yarn-project/pxe/src/note_processor/note_processor.test.ts
@@ -43,7 +43,7 @@ describe('Note Processor', () => {
   const firstBlockDataStartIndex = (firstBlockNum - 1) * numCommitmentsPerBlock;
   const firstBlockDataEndIndex = firstBlockNum * numCommitmentsPerBlock;
 
-  const computeMockNoteHash = (note: Note) => Fr.fromBuffer(pedersenHash(note.items.map(i => i.toBuffer())));
+  const computeMockNoteHash = (note: Note) => pedersenHash(note.items.map(i => i.toBuffer()));
 
   // ownedData: [tx1, tx2, ...], the numbers in each tx represents the indices of the note hashes the account owns.
   const createEncryptedLogsAndOwnedL1NotePayloads = (ownedData: number[][], ownedNotes: L1NotePayload[]) => {
diff --git a/yarn-project/simulator/src/avm/avm_simulator.test.ts b/yarn-project/simulator/src/avm/avm_simulator.test.ts
index 8a56550155ae..bfe7b98f704c 100644
--- a/yarn-project/simulator/src/avm/avm_simulator.test.ts
+++ b/yarn-project/simulator/src/avm/avm_simulator.test.ts
@@ -118,7 +118,7 @@ describe('AVM simulator', () => {
     describe.each([
       ['avm_poseidon_hash', poseidonHash],
       ['avm_pedersen_hash', pedersenHash],
-    ])('Hashes with field returned in noir contracts', (name: string, hashFunction: (data: Buffer[]) => Buffer) => {
+    ])('Hashes with field returned in noir contracts', (name: string, hashFunction: (data: Buffer[]) => Fr) => {
       it(`Should execute contract function that performs ${name} hash`, async () => {
         const calldata = [new Fr(1), new Fr(2), new Fr(3)];
         const hash = hashFunction(calldata.map(f => f.toBuffer()));
diff --git a/yarn-project/simulator/src/avm/opcodes/hashing.test.ts b/yarn-project/simulator/src/avm/opcodes/hashing.test.ts
index 0c7b363df048..25e4a71a68e7 100644
--- a/yarn-project/simulator/src/avm/opcodes/hashing.test.ts
+++ b/yarn-project/simulator/src/avm/opcodes/hashing.test.ts
@@ -45,7 +45,7 @@ describe('Hashing Opcodes', () => {
       await new Poseidon2(indirect, dstOffset, hashOffset, args.length).execute(context);
 
       const result = context.machineState.memory.get(dstOffset);
-      expect(result).toEqual(new Field(toBigIntBE(expectedHash)));
+      expect(result).toEqual(new Field(expectedHash));
     });
 
     it('Should hash correctly - indirect', async () => {
@@ -63,7 +63,7 @@ describe('Hashing Opcodes', () => {
       await new Poseidon2(indirect, dstOffset, hashOffset, args.length).execute(context);
 
       const result = context.machineState.memory.get(dstOffset);
-      expect(result).toEqual(new Field(toBigIntBE(expectedHash)));
+      expect(result).toEqual(new Field(expectedHash));
     });
   });
 
@@ -225,7 +225,7 @@ describe('Hashing Opcodes', () => {
       await new Pedersen(indirect, dstOffset, hashOffset, args.length).execute(context);
 
       const result = context.machineState.memory.get(dstOffset);
-      expect(result).toEqual(new Field(toBigIntBE(expectedHash)));
+      expect(result).toEqual(new Field(expectedHash));
     });
 
     it('Should hash correctly - indirect', async () => {
@@ -244,7 +244,7 @@ describe('Hashing Opcodes', () => {
       await new Pedersen(indirect, dstOffset, hashOffset, args.length).execute(context);
 
       const result = context.machineState.memory.get(dstOffset);
-      expect(result).toEqual(new Field(toBigIntBE(expectedHash)));
+      expect(result).toEqual(new Field(expectedHash));
     });
   });
 });
diff --git a/yarn-project/simulator/src/client/private_execution.test.ts b/yarn-project/simulator/src/client/private_execution.test.ts
index 501c5b908a47..a8e03dcdfc59 100644
--- a/yarn-project/simulator/src/client/private_execution.test.ts
+++ b/yarn-project/simulator/src/client/private_execution.test.ts
@@ -178,7 +178,7 @@ describe('Private Execution test suite', () => {
     return trees[name];
   };
 
-  const hashFields = (data: Fr[]) => Fr.fromBuffer(pedersenHash(data.map(f => f.toBuffer())));
+  const hashFields = (data: Fr[]) => pedersenHash(data.map(f => f.toBuffer()));
 
   beforeAll(() => {
     logger = createDebugLogger('aztec:test:private_execution');
diff --git a/yarn-project/simulator/src/client/simulator.test.ts b/yarn-project/simulator/src/client/simulator.test.ts
index 4eec4b5a3d17..b8192633373a 100644
--- a/yarn-project/simulator/src/client/simulator.test.ts
+++ b/yarn-project/simulator/src/client/simulator.test.ts
@@ -23,7 +23,7 @@ describe('Simulator', () => {
   const ownerNullifierSecretKey = GrumpkinScalar.random();
   const ownerNullifierPublicKey = Point.random();
 
-  const hashFields = (data: Fr[]) => Fr.fromBuffer(pedersenHash(data.map(f => f.toBuffer())));
+  const hashFields = (data: Fr[]) => pedersenHash(data.map(f => f.toBuffer()));
 
   beforeEach(() => {
     oracle = mock<DBOracle>();
diff --git a/yarn-project/simulator/src/public/index.test.ts b/yarn-project/simulator/src/public/index.test.ts
index 4a528e1f1873..860520256684 100644
--- a/yarn-project/simulator/src/public/index.test.ts
+++ b/yarn-project/simulator/src/public/index.test.ts
@@ -332,7 +332,7 @@ describe('ACIR public execution simulator', () => {
 
       const expectedNoteHash = pedersenHash([amount.toBuffer(), secretHash.toBuffer()]);
       const storageSlot = new Fr(5); // for pending_shields
-      const expectedInnerNoteHash = pedersenHash([storageSlot.toBuffer(), expectedNoteHash]);
+      const expectedInnerNoteHash = pedersenHash([storageSlot, expectedNoteHash].map(f => f.toBuffer()));
       expect(result.newCommitments[0].value.toBuffer()).toEqual(expectedInnerNoteHash);
     });
 
@@ -365,7 +365,7 @@ describe('ACIR public execution simulator', () => {
 
       const expectedNewMessage = new L2ToL1Message(
         portalContractAddress,
-        Fr.fromBuffer(pedersenHash(params.map(a => a.toBuffer()))),
+        pedersenHash(params.map(a => a.toBuffer())),
       );
 
       expect(result.newL2ToL1Messages[0]).toEqual(expectedNewMessage);
@@ -478,7 +478,7 @@ describe('ACIR public execution simulator', () => {
 
         let root = messageKey ?? preimage.hash();
         for (const sibling of siblingPathBuffers) {
-          root = Fr.fromBuffer(pedersenHash([root.toBuffer(), sibling]));
+          root = pedersenHash([root.toBuffer(), sibling]);
         }
         commitmentsDb.getL1ToL2Message.mockImplementation(() => {
           return Promise.resolve(new MessageLoadOracleInputs(preimage, 0n, siblingPath));
diff --git a/yarn-project/simulator/src/utils.ts b/yarn-project/simulator/src/utils.ts
index a47e4e390ba3..ad65917f0130 100644
--- a/yarn-project/simulator/src/utils.ts
+++ b/yarn-project/simulator/src/utils.ts
@@ -14,5 +14,5 @@ export function computeSlotForMapping(
     toField: () => Fr;
   },
 ) {
-  return Fr.fromBuffer(pedersenHash([mappingSlot, key.toField()].map(field => field.toBuffer())));
+  return pedersenHash([mappingSlot, key.toField()].map(field => field.toBuffer()));
 }