diff --git a/contracts/Events.sol b/contracts/Events.sol
index a9edc67..00201ad 100644
--- a/contracts/Events.sol
+++ b/contracts/Events.sol
@@ -8,7 +8,8 @@ import "./Operations.sol";
 interface Events {
     event NewToken(address tokenAddr, uint16 tokenId);
     event NewTradingPair(uint16 baseTokenId, uint16 quoteTokenId);
-    event Deposit(uint16 tokenId, address to, uint256 amount); // emit tokenId or tokenAddr?
+    event RegisterUser(address ethAddr, uint16 userId, string bjjPubkey);
+    event Deposit(uint16 tokenId, string to, uint256 amount); // emit tokenId or tokenAddr?
     event Withdraw(uint16 tokenId, address to, uint256 amount); // emit tokenId or tokenAddr?
 
     /// @notice New priority request event. Emitted when a request is placed into mapping
diff --git a/contracts/Fluidex.sol b/contracts/Fluidex.sol
index aa823ca..faf2191 100644
--- a/contracts/Fluidex.sol
+++ b/contracts/Fluidex.sol
@@ -14,6 +14,7 @@ import "hardhat/console.sol";
 import "./Utils.sol";
 
 import "./Storage.sol";
+import "./UserInfo.sol";
 import "./Config.sol";
 import "./Events.sol";
 
@@ -25,11 +26,16 @@ contract Fluidex is ReentrancyGuard, Storage, Config, Events, Ownable {
     using SafeMath for uint256;
 
     uint16 constant TOKEN_NUM_LIMIT = 65535;
+    uint16 constant USER_NUM_LIMIT = 65535;
 
     uint16 public tokenNum;
     mapping(uint16 => address) public tokenIdToAddr;
     mapping(address => uint16) public tokenAddrToId;
 
+    uint16 public userNum;
+    mapping(uint16 => UserInfo) public userIdToUserInfo;
+    mapping(string => uint16) public userBjjPubkeyToUserId;
+
     function initialize() external {}
 
     function addToken(address tokenAddr)
@@ -58,9 +64,24 @@ contract Fluidex is ReentrancyGuard, Storage, Config, Events, Ownable {
         emit NewTradingPair(baseTokenId, quoteTokenId);
     }
 
+    // TODO: check signature?
+    function registerUser(address ethAddr, string memory bjjPubkey) internal {
+        userNum++;
+        require(userBjjPubkeyToUserId[bjjPubkey] == 0, "user existed");
+        require(userNum < USER_NUM_LIMIT, "user num limit reached");
+
+        uint16 userId = userNum;
+        userIdToUserInfo[userId] = UserInfo({
+            ethAddr: ethAddr,
+            bjjPubkey: bjjPubkey
+        });
+        userBjjPubkeyToUserId[bjjPubkey] = userId;
+        emit RegisterUser(ethAddr, userId, bjjPubkey);
+    }
+
     // 0 tokenId means native ETH coin
     // TODO: zkSync uses uint128 for amount
-    function registerDeposit(uint16 tokenId, address to, uint256 amount) internal {
+    function registerDeposit(uint16 tokenId, string memory to, uint256 amount) internal {
         // Priority Queue request
         Operations.Deposit memory op =
             Operations.Deposit({
@@ -75,10 +96,15 @@ contract Fluidex is ReentrancyGuard, Storage, Config, Events, Ownable {
     }
 
     /// @param to the L2 address of the deposit target.
-    // TODO: change to L2 address
-    function depositETH(address to) external payable {
+    function depositETH(
+        string calldata to // L2 bjjPubkey
+    ) external payable {
         // You must `approve` the allowance before calling this method
-        require(to != address(0), "invalid address");
+
+        if (userBjjPubkeyToUserId[to] == 0) {
+            registerUser(msg.sender, to);
+        }
+
         // 0 tokenId means native ETH coin
         registerDeposit(0, to, msg.value);
     }
@@ -87,13 +113,18 @@ contract Fluidex is ReentrancyGuard, Storage, Config, Events, Ownable {
     /// @param amount the deposit amount.
     function depositERC20(
         IERC20 token,
-        address to, // TODO: change to L2 address
+        string calldata to, // L2 bjjPubkey
         uint128 amount
     ) external nonReentrant {
         // You must `approve` the allowance before calling this method
-        require(to != address(0), "invalid address");
+
         uint16 tokenId = tokenAddrToId[address(token)];
         require(tokenId != 0, "invalid token");
+
+        if (userBjjPubkeyToUserId[to] == 0) {
+            registerUser(msg.sender, to);
+        }
+
         uint256 balanceBeforeDeposit = token.balanceOf(address(this));
         token.safeTransferFrom(msg.sender, address(this), amount);
         uint256 balanceAfterDeposit = token.balanceOf(address(this));
diff --git a/contracts/Operations.sol b/contracts/Operations.sol
index 6750300..d360c4d 100644
--- a/contracts/Operations.sol
+++ b/contracts/Operations.sol
@@ -17,7 +17,8 @@ library Operations {
         uint32 accountId;
         uint16 tokenId;
         uint256 amount; // TODO: zkSync uses uint128 for amount
-        address owner;
+        // address owner;
+        string owner;
     }
 
     /// Serialize deposit pubdata
diff --git a/contracts/UserInfo.sol b/contracts/UserInfo.sol
new file mode 100644
index 0000000..5ae49a0
--- /dev/null
+++ b/contracts/UserInfo.sol
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.6.0 <0.8.0;
+
+/// @title Fluidex userinfo contract
+struct UserInfo {
+    address ethAddr;
+    string bjjPubkey;
+}
diff --git a/test/token.js b/test/token.js
index d861a7c..b396aa7 100644
--- a/test/token.js
+++ b/test/token.js
@@ -1,4 +1,5 @@
 const { expect } = require("chai");
+const { randomBytes } = require("@ethersproject/random");
 
 describe("Fluidex", () => {
   let fluidex;
@@ -7,6 +8,7 @@ describe("Fluidex", () => {
   let senderAddr;
   let acc2;
   let acc2addr;
+  const mockBjj = "randomBytes(32)";
   const initialBalance = 1000;
   const decimal = 2;
 
@@ -50,10 +52,11 @@ describe("Fluidex", () => {
     await expect(
       fluidex
         .connect(acc2)
-        .depositERC20(erc20Mock.address, acc2addr, depositAmount)
+        .depositERC20(erc20Mock.address, mockBjj, depositAmount)
     )
       .to.emit(fluidex, "Deposit")
-      .withArgs(tokenId, acc2addr, depositAmount);
+      .withArgs(tokenId, mockBjj, depositAmount);
+
     await expect(
       fluidex.withdrawERC20(erc20Mock.address, acc2addr, withdrawAmount)
     )
@@ -69,10 +72,10 @@ describe("Fluidex", () => {
     await expect(
       fluidex
         .connect(acc2)
-        .depositETH(acc2addr, {value: depositAmount})
+        .depositETH(mockBjj, {value: depositAmount})
     )
       .to.emit(fluidex, "Deposit")
-      .withArgs(0, acc2addr, depositAmount);
+      .withArgs(0, mockBjj, depositAmount);
 
     await expect(
       fluidex.withdrawETH(acc2addr, withdrawAmount)