Polygon zkEVM DAI Bridge

Introduction

Native DAI implementation is consist of two smart contracts:

1. L1Escrow: This contract is deployed on Ethereum mainnet and interact directly with Spark protocol.
2. L2Dai: This contract is deployed on Polygon zkEVM.

With Native DAI, user can do the following:

1. Bridge DAI from Ethereum mainnet to Polygon zkEVM via L1Escrow contract.
2. Bridge DAI from Polygon zkEVM to Ethereum mainnet via L2Dai contract.

Get started

Requirements

This repository is using foundry. You can install foundry via foundryup.

Setup

Clone the repository:

git clone git@github.com:pyk/zkevm-dai.git
cd zkevm-dai/

Install the dependencies:

forge install

Tests

Create .env with the following contents:

ETH_RPC_URL=""
ZKEVM_RPC_URL="https://zkevm-rpc.com"
ETHERSCAN_API_KEY=""

Use the following command to run the test:

forge test

You can also run individual test using the following command:

forge test --fork-url $ETH_RPC_URL --match-test testSendExcessYield -vvvv

forge test --fork-url "https://zkevm-rpc.com" --match-path test/L2Dai.t.sol --match-test testBridgeWithMockedBridge -vvvv

Note You can set ETHERSCAN_API_KEY to helps you debug the call trace.

Deployment

Use the following command to deploy on Goerli:

forge script ...

Contract addresses

Smart contract	Network	Address
DAI	Mainnet	0x6B175474E89094C44Da98b954EedeAC495271d0F
sDAI	Mainnet	0x83f20f44975d03b1b09e64809b757c47f942beea
Polygon ZkEVM Bridge	Mainnet	0x2a3dd3eb832af982ec71669e178424b10dca2ede
	zkEVM Mainnet	0x2a3dd3eb832af982ec71669e178424b10dca2ede
L1Escrow	Mainnet	0x4a27ac91c5cd3768f140ecabde3fc2b2d92edb98
L2Dai	zkEVM Mainnet	0x744c5860ba161b5316f7e80d9ec415e2727e5bd5

Testnet Contract addresses

Smart contract	Network	Address
DAI	Goerli	0x11fE4B6AE13d2a6055C8D9cF65c55bac32B5d844
sDAI	Goerli	0xD8134205b0328F5676aaeFb3B2a0DC15f4029d8C
Polygon ZkEVM Bridge	Goerli	0xF6BEEeBB578e214CA9E23B0e9683454Ff88Ed2A7
	zkEVM Testnet	0xF6BEEeBB578e214CA9E23B0e9683454Ff88Ed2A7
L1Escrow	Goerli	0x2929b2635E51f2dA1373A76F166A237322694fA6
L2Dai	zkEVM Testnet	0x755CB8A808c99706afAA34547204f17cD33C6316

Known Issues

Rounding Issue

When we deposit x amount of DAI to sDAI, we will get y amount of sDAI based on the current exchange rate r. Due to how y is rounded down by sDAI, there is possibility that when we redeem y amount of sDAI we will get x' = x - 1 amount of DAI.

For, example:

uint256 x = 1000000000000000001;
uint256 y = sdai.deposit(x);
uint255 x_ = sdai.redeem(y); // x_ = 1000000000000000000

Note See sDAI.t.sol for more details.

Ofcourse, r will be increased over time and this 1 wei will be covered.

To make sure that bridged DAI is always 1:1, it is advised to donate small amount of DAI on L1Escrow on the first time it get deployed (e.g. 0.01 DAI).

sendExcessYield will send excess yield if the total yield is more than 0.05 DAI and will leave 0.01 DAI from the yield in L1Escrow.

Locked DAI in L1Escrow may greater than totalProtocolDAI

Currently there is no way to check the maximum deposit amount of sDAI. sdai.maxDeposit(address) is hardcoded to type(uint256).max.

sdai.deposit(amount, recipient) may reverted and it is possible that total amount of locked DAI in the L1Escrow is greater than the specified totalProtocolDAI.