PulseChain Bridge Explained: How It Works and What to Know

The PulseChain Bridge is a cross-chain transfer protocol between PulseChain and Ethereum that allows transferring ETH and ERC-20 tokens in either direction between these EVM-compatible networks. The PulseChain Bridge is one of the main building blocks that was deployed in parallel with PulseChain when it was launched.

What PulseChain Is

PulseChain is a proof-of-stake blockchain developed by Richard Heart, the same person behind HEX. PulseChain is a full-state fork of Ethereum meaning that upon forking, PulseChain cloned the state of Ethereum at the point of its fork block and replicated it on the new blockchain. As a result, each Ethereum address has a clone of all of its ETH balances and tokens from day one of PulseChain's life.

PulseChain uses PLS as a gas token while Ethereum uses ETH. Both chains are EVM-compatible so Ethereum smart contracts and Ethereum tools can work on PulseChain almost without changes. One of the key characteristics of PulseChain is its much lower transaction fees compared to Ethereum.

How the PulseChain Bridge Works

The PulseChain Bridge uses a lock-and-mint mechanism. When you transfer your Ethereum tokens to the bridge contract on Ethereum, they are locked in the contract. Then the bridge mints the equivalent amount of bridged tokens on PulseChain and sends them to your address. Bridged tokens are a claim on the tokens locked in the bridge contract on Ethereum. The reverse procedure — unlocking the tokens — works similarly: when you bridge back your tokens, the bridged tokens on PulseChain get burned and the underlying tokens get unlocked on Ethereum.

This implies that the value of bridged tokens on PulseChain is dependent on the value of the underlying tokens and is only as safe as the bridge contract itself on Ethereum. The bridge contract is the single point of failure of such a design. If the contract is exploited by a hacker, the tokens get drained and the bridged tokens lose their value.

That's how the typical lock-and-mint cross-chain transfer protocol works. There's nothing specific to the PulseChain Bridge here. For PLS as a native token of PulseChain, the bridge works a bit differently because PLS is not native on Ethereum.

The Official Bridge and Where to Find It

The official PulseChain Bridge interface is available at bridge.pulsechain.com. This is the interface maintained by the developers of PulseChain. It makes sense to use the official bridge interface instead of unofficial ones because there's always a risk that the interface might work differently and could be malicious.

To use the bridge interface, you need a Web3 wallet (such as MetaMask). Both Ethereum and PulseChain networks should be added to your wallet. PulseChain network parameters: chain ID 369, RPC URL rpc.pulsechain.com, currency symbol PLS. These can be added to MetaMask manually or via Chainlist.

Bridging from Ethereum to PulseChain: Step-by-Step Guide

Transferring tokens from Ethereum to PulseChain involves a sequence of actions that is pretty similar no matter which token you transfer.

Step 1: Connect Your Wallet

Open bridge.pulsechain.com and connect your wallet. Make sure the wallet is connected to the Ethereum mainnet network before bridging tokens to PulseChain. The bridge interface recognizes the active network automatically.

Step 2: Select the Token and Amount

Select the token that you want to bridge from the list of supported tokens in the drop-down menu. Not all tokens on Ethereum are included in the list of supported tokens on the bridge. For unsupported tokens, you can enter the token contract address manually. Type the amount of tokens to transfer. The bridge will show you the output amount on PulseChain.

Step 3: Approve Token Spending

If you are bridging a token for the first time, you need to approve the bridge contract to spend the token from your wallet. This is an Ethereum transaction that requires some gas. You need to do it only once per token per wallet.

Step 4: Confirm the Bridge Transaction

After you approve the spending of the tokens, you need to submit the bridge transaction itself. You will see the gas fee required for the transaction in the MetaMask wallet. When you submit the transaction, it is broadcast to Ethereum and waits for inclusion in a block. After the required number of confirmations, the bridge mints the bridged tokens on PulseChain and sends them to your address.

Step 5: Check Receipt on PulseChain

Switch your wallet to the PulseChain network and see if you've got your tokens there. In case the token does not appear in your wallet, you need to add it manually via the token contract address on PulseChain. PulseScan (scan.pulsechain.com) is the block explorer for PulseChain and can show you the history of your transactions and tokens in your wallet on PulseChain.

Bridging from PulseChain to Ethereum

The procedure of bridging in the opposite direction is basically the same, except the PulseChain side becomes the source network. Note that the transaction fees for the PulseChain side are paid in PLS. This is much cheaper than Ethereum transaction fees. Also, the Ethereum side of the transaction requires some gas which is paid in ETH. This is an important thing to keep in mind since if your Ethereum wallet has no ETH, you won't be able to complete your withdrawal on the Ethereum side.

The bridge uses the message passing mechanism between the two networks. When your PulseChain transaction gets confirmed, a message is sent to the bridge on Ethereum asking to unlock the underlying tokens. The message relay mechanism takes several minutes and can be observed in the bridge interface or on PulseScan.

Fees in PulseChain Bridge Usage

Bridging always involves fees on both sides of the transaction, though the cost and nature of those fees depend on the direction.

1. Ethereum Gas Fees: Transactions on the Ethereum side of the bridge — either locking the tokens when bridging to PulseChain or unlocking tokens when bridging back — require ETH gas. Ethereum transaction fees are dynamic and depend on the current network conditions, costing a few dollars in non-congested periods and significantly more during high traffic. The token approval transaction also requires ETH gas.

2. PulseChain Gas Fees: Transactions on the PulseChain side of the bridge are paid in PLS. PulseChain fees are very low compared to Ethereum — fractions of a cent per transaction. You need some PLS in your wallet before you can do any transaction on PulseChain including bridging.

3. Bridge Protocol Fee: The official PulseChain Bridge takes a small fee from the transferred amount as a protocol fee to maintain the bridge. The exact protocol fee is displayed on the bridge interface before the transaction is submitted. The protocol fee for small transactions can be a noticeable percent of the total amount, which should be taken into account before bridging small amounts.

What Tokens Can Be Bridged

The PulseChain Bridge supports ETH and ERC-20 tokens from Ethereum. Since PulseChain is a full-state fork of Ethereum, most ERC-20 tokens already exist on PulseChain as forked tokens. Bridging an ERC-20 token to PulseChain does not produce the forked version of that token that already exists on PulseChain, but creates a new version — a wrapped token that is backed by the tokens locked in the bridge contract on Ethereum.

This makes an important distinction between two versions of the same token on PulseChain:

• Forked Token: The token copy that was created along with the fork on PulseChain.

• Bridged Token: A wrapped token created by the bridge and backed by the tokens locked in the bridge contract on Ethereum.

These tokens can have different prices and different liquidity pools on PulseX, the main decentralized exchange on PulseChain. When bridging a token, you should check which version is acceptable or preferred for the application that you want to use on PulseChain.

How Long Does Bridging Take

Bridging time is determined by the Ethereum block confirmation time and the relay mechanism of the bridge. When bridging to PulseChain, the bridge typically waits for a certain number of block confirmations on Ethereum before minting the bridged tokens on PulseChain. Under normal circumstances, the entire process takes 5 to 20 minutes.

When bridging back to Ethereum, the same applies in the inverse order. PulseChain block times are much shorter than Ethereum block times, so the initial confirmation takes place much faster. The actual delay is in the message relay to Ethereum and waiting for Ethereum transaction confirmation. Total time is around 10 to 30 minutes.

If your transfer seems to be stuck, you can see the current status of the transaction in the bridge interface or check it on PulseScan / Etherscan. Most likely, the transaction is simply awaiting confirmations.

PulseX and the DeFi Ecosystem on PulseChain

PulseX is the main decentralized exchange on PulseChain, forked from Uniswap v2. PulseX serves as a liquidity provider for tokens on PulseChain, both forked and bridged. Understanding PulseX is important when using the PulseChain Bridge because PulseX is the final destination for bridged tokens.

Liquidity provided on PulseX is separate from the liquidity on Ethereum DEXes such as Uniswap. A token can have good liquidity on Ethereum but very poor liquidity on PulseChain, which affects slippage when swapping bridged tokens. You should check PulseX liquidity for the token that you want to bridge to know what price impact to expect.

Risks of Using the PulseChain Bridge

• Smart Contract Risk: The bridge contracts on both Ethereum and PulseChain store locked tokens. A vulnerability in any of these contracts can be exploited by an attacker, leading to draining the locked funds and making the bridged tokens useless.

• Token Confusion Risk: Since both forked tokens and bridged tokens exist for the same ERC-20 token on PulseChain, there is a possibility to confuse them. Sending the wrong token version to a protocol can result in errors.

• Liquidity / Exit Risk: After bridging tokens to PulseChain, you might want to get them back to Ethereum in the future. The bridge must have enough liquidity to allow the reverse transfer. Also, if the PulseChain ecosystem becomes underdeveloped, exiting back to Ethereum with a reasonable price might be difficult.

• Network and Regulatory Risk: PulseChain is a relatively new network with a small development community and low institutional support. Regulatory developments can influence access to PulseChain services or the bridge itself.

Common Mistakes When Using the Bridge

• No PLS for gas on PulseChain: You won't be able to pay for any transaction on PulseChain (including bridging back) if your PulseChain wallet doesn't have PLS.

• No ETH for gas on Ethereum: You won't be able to withdraw your tokens to Ethereum if your Ethereum wallet is empty.

• Using an unofficial interface: Phishing websites mimic the official bridge interface and route funds to attacker-controlled contracts. Always use bridge.pulsechain.com.

• Bridging the wrong token version: Bridging the forked version when the application needs the bridged version (or vice versa) leads to having a token that is not recognized by the application.

Summary

The PulseChain Bridge is a direct way of transferring ETH and ERC-20 tokens between Ethereum and PulseChain using a lock-and-mint mechanism. The official bridge interface is available at bridge.pulsechain.com. Key points:

• You need both ETH and PLS for gas.

• Forked tokens and bridged tokens are different assets on PulseChain.

• Transfers take 5 to 30 minutes under normal conditions.