2022-04-27

Published on Wednesday, April 27, 2022

In Arweave Infrastructure

Arweave Development Tutorial: How to Use everPay-js for Atomic Swap

everPay is a decentralized cross-chain financial protocol built on Arweave that supports Bundle transactions and naturally supports atomic swaps between tokens. Unlike other traditional blockchains where transfers have to wait for packaging, everPay transactions are verified and cached meticulously by everPay servers, and assets arrive in real-time. Therefore, there is no need to wait for transactions to be packaged.

What is an atomic swap?

The bundle is a many-to-many transaction format where if any subtransaction in a Bundle fails, the entire transaction is rolled back. When making a Bundle transaction, the user only needs to consider their balance and expenses and does not need to worry about the counterparty defaulting. If a user signs a Bundle transaction that pays 1000 USDT and receives 0.1 ETH when the transaction is executed.

If the user does not receive 0.1 ETH, his payment of 1000 USDT will be rolled back. The Bundle transaction will be completed successfully only if the user’s payments and receipts meet the order conditions.

everPay-js is a js-sdk open source library for everPay. With everPay-js functions, you can quickly implement an atomic token swap. The following section describes how to perform an atomic swap between two wallets, A and B.

Show me the code????

https://github.com/everFinance/everpay-example/blob/main/javascript/Bundle.js

Prerequisites

Wallets

everPay protocol supports both Ethereum and Arweave wallet addresses, and the following example uses Ethereum addresses.

Wallet address A: 0x73f45F01C66c81B4016858C63E695CDfEe347F54, with private key: ba7da8e8893b516f43f73a8d69ca4ed4ffd60e55f6a739fa707350f1add89f2f
Wallet address B: 0x06eACBB9c550F0a014DC1BF0244312a96DF1a411, with private key: dfe071748c3d7c9110ecc214305645a7a63f4203792e30d8207dd412ec8c0908

Test token claiming

The following examples will be performed at everPay Testnet. If you need some test tokens, you can apply for test tokens of 1000 USDT and 0.1 ETH by reaching out to @Xaber | everFinance#4893 at the dev channel in everPay discord.

Discord Dev Channel：https://discord.gg/dCreupzseF

Test token transfer

Use everPay dev network https://app-dev.everpay.io/transfer to transfer 1000 USDT to wallet address A 0x73..F54. The transfer procedure is shown below:

Use the everPay dev network https://app-dev.everpay.io/transfer to transfer 0.1 ETH to wallet address B 0x06…411.

At this point, wallet A has 1000 USDT and wallet B has 0.1 ETH on everPay

Atomic Swap

Initialize everPay with Ethereum wallet

import { ethers } from ‘ethers’
import Everpay from ‘everpay’

const genEverpay = (wallet) => {
const provider = new ethers.providers.InfuraProvider(‘kovan’)
const signer = new ethers.Wallet(wallet.privateKey, provider)
const everpay = new Everpay({
account: wallet.address,
ethConnectedSigner: signer, chainType: ‘ethereum’,
debug: true
})
return everpay
}

const walletA = {
address: ‘0x73f45F01C66c81B4016858C63E695CDfEe347F54’,
privateKey: ‘ba7da8e8893b516f43f73a8d69ca4ed4ffd60e55f6a739fa707350f1add89f2f’
}

const walletB = {
address: ‘0x06eACBB9c550F0a014DC1BF0244312a96DF1a411’,
privateKey: ‘dfe071748c3d7c9110ecc214305645a7a63f4203792e30d8207dd412ec8c0908’
}

const everpayA = genEverpay(walletA)
const everpayB = genEverpay(walletB)

We initialize two everPay instances of everpayA and everpayB with their private keys. The initialized everPay instances can sign orders and send transactions to the everPay node.

Note: When debugging parameter in the new everPay is true, everPay Testnet will be used in the development. If you need to use mainnet, please set debug to false.

Initialize everPay with Arweave wallet

The jwk parameter is RSA Key, generated on your own. Skip the following code if you are not using Arweave wallet.

const arWallet = {
address: ‘5NPqYBdIsIpJzPeYixuz7BEH_W7BEk_mb8HxBD3OHXo’,
jwk: { kty: ‘RSA’, n: ‘odtNk…’, e: ‘AQAB’, d: ‘mTc…’, p: ‘znk…’, q: ‘yK5…’, dp: ‘OrD…’, dq: ‘cPC…’, qi: ‘Qzp…’ }
}

const everpayC = new Everpay({
account: arWallet.address,
arJWK: arWallet.jwk, chainType: ‘arweave’,
debug: true
})

Generate bundle data for atomic swap

Transfer 1000 USDT from walletA’s everPay wallet to walletB’s everPay wallet
Transfer 0.1 ETH from walletB’s everPay wallet to walletA’s everPay wallet

const bundleData = await everpayA.getBundleData([
{
symbol: ‘USDT’,
from: walletA.address,
to: walletB.address,
amount: ‘1000’
}, {
symbol: ‘ETH’,
from: walletB.address,
to: walletA.address,
amount: ‘0.1’
}
])

The above code is a Bundle transaction describing a transfer of 1000 USDT from A to B and a transfer of 0.1 ETH from B to A.

Sign bundle data

For a Bundle transaction to be successfully executed, all the transferring parties need to provide signatures. The “from” addresses of the transferring parties of our Bundle are walletA and walletB respectively, so they need to sign the Bundle, and the signing method is shown below.

const bundleDataWithSigA = await everpayA.signBundleData(bundleData)

const bundleDataWithSigB = await everpayB.signBundleData(bundleDataWithSigA)

The signBundleData function will automatically send the signature of walletA (everpayA) to bundleDataWithSigA. After the two signatures above, bundleDataWithSigB will contain the signatures of both walletA and walletB accounts for the Bundle transaction.

Post signed bundle data

Finally, we post this Bundle to everPay to complete the atomic swap of 1000 USDT and 0.1 ETH for walletA and walletB in the everPay network.

const bundleResult = await everpayA.bundle({
symbol: ‘ETH’,
to: walletA.address,
amount: ‘0’,
data: {
bundle: bundleDataWithSigB
}
})

const everHash = bundleResult.everHash
console.log(everHash)

The bundleDataWithSigB containing the two signatures will be sent to the everPay node via the bundle function. Please fill in the symbol, to, and amount fields in the above code to follow the tutorial. A bundle is an internal transaction, see more details in our documentation.

Please keep the output everHash and use everHash to check the status of the bundle transaction in your browser.

Check transaction status at everScan

Open up everPay dev Blockchain Explorer, and search for everHash

View transaction status

Check balance changes

Call the everPay balances() function to see all token balances under an account.

// ETH 0.1
await everpayA.balances()

// USDT 1000
await everpayB.balances()

Now, walletA has 0.1 ETH in everPay and walletB has 1000 USDT in everPay.

walletA and walletB successfully complete an atomic swap of ETH-USDT via Bundle in the everPay network.

Demo code

https://github.com/everFinance/everpay-example/blob/main/javascript/bundle.js

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