diff --git a/contracts/Mixer.sol b/contracts/Mixer.sol
index 22a9180..971c0d0 100644
--- a/contracts/Mixer.sol
+++ b/contracts/Mixer.sol
@@ -61,7 +61,7 @@ contract Mixer is MerkleTreeWithHistory {
     @dev Deposit funds into mixer. The caller must send (for ETH) or approve (for ERC20) value equal to or `denomination` of this mixer.
     @param _commitment the note commitment, which is PedersenHash(nullifier + secret)
   */
-  function deposit(bytes32 _commitment) public payable {
+  function deposit(bytes32 _commitment) external payable {
     require(!isDepositsDisabled, "deposits are disabled");
     require(!commitments[_commitment], "The commitment has been submitted");
 
@@ -83,7 +83,7 @@ contract Mixer is MerkleTreeWithHistory {
       - the receiver of funds
       - optional fee that goes to the transaction sender (usually a relay)
   */
-  function withdraw(bytes memory _proof, bytes32 _root, bytes32 _nullifierHash, address payable _receiver, address payable _relayer, uint256 _fee, uint256 _refund) public payable {
+  function withdraw(bytes calldata _proof, bytes32 _root, bytes32 _nullifierHash, address payable _receiver, address payable _relayer, uint256 _fee, uint256 _refund) external payable {
     require(_fee <= denomination, "Fee exceeds transfer value");
     require(!nullifierHashes[_nullifierHash], "The note has been already spent");
     require(isKnownRoot(_root), "Cannot find your merkle root"); // Make sure to use a recent one
@@ -98,7 +98,7 @@ contract Mixer is MerkleTreeWithHistory {
   function _processWithdraw(address payable _receiver, address payable _relayer, uint256 _fee, uint256 _refund) internal;
 
   /** @dev whether a note is already spent */
-  function isSpent(bytes32 _nullifierHash) public view returns(bool) {
+  function isSpent(bytes32 _nullifierHash) external view returns(bool) {
     return nullifierHashes[_nullifierHash];
   }