Transfer cross-chain value
This section will explain how to enable ERC-20 value transfer between Kairos network and your ServiceChain with the provided test code. You will add KAIA to the operator account and deploy bridge and ERC-20 contracts. Then you will register the contract address on SCN. And you will test an ERC-20 value transferring.
Prerequisites
- We assume that you installed the ServiceChain, and connected the ServiceChain to the Kairos EN by the instructions in Connecting to Kairos.
- Clone the repository servicechain-value-transfer-examples.
- Install
Node.js
(v14) andnpm
(How to install)- This example leverages two packages, axios and caver-js, which both support v14.
ERC-20 Token Transfer (one-step)
Step 1: Add KAIA to the operator accounts.
Connect to the SCN and check the account addresses by executing subbridge.parentOperator
and subbridge.childOperator
.
$ kscn attach --datadir ~/data> subbridge.childOperator"0x10221f7f9355017cd0c11444e7eecb99621bacce"> subbridge.parentOperator"0x3ce216beeafc62d20547376396e89528e1d778ca"
subbridge.parentOperator
and subbridge.childOperator
must have enough KAIA to send a transaction. Note that subbridge.parentOperator
is an account on the Kairos network, and subbridge.childOperator
is an account on the ServiceChain network.
Create a test account at https://toolkit.kaia.io/account/accountKeyLegacy and get test KAIA from the faucet. Then send some KAIA to the parentOperator
. childOperator
has to get KAIA from the test account generated by homi
(Refer to EN Setup and SCN Connection Guide).
$ kscn account import ~/homi-output/keys_test/testkey1Your new account is locked with a password. Please give a password. Do not forget this password.Passphrase:Repeat passphrase:Address: {80119c31cdae67c42c8296929bb4f89b2a52cec4}
$ kscn attach --datadir ~/data> personal.unlockAccount("80119c31cdae67c42c8296929bb4f89b2a52cec4")Unlock account 80119c31cdae67c42c8296929bb4f89b2a52cec4Passphrase:True> kaia.sendTransaction({from:"80119c31cdae67c42c8296929bb4f89b2a52cec4", to:subbridge.childOperator, value: web3.toPeb(1000, "KAIA")})"0x84caab84ebf0c4bb4ecf0a7849f1de3e479f1863a95f70c51047a7ca7bc64b33"
Check if the operator accounts have enough balance. You can query from the console of the SCN node where the subbridge is installed as follows:
> kaia.getBalance(subbridge.childOperator)1e+21> subbridge.childOperatorBalance1e+21> subbridge.parentOperatorBalance1e+18
Step 2: Deploy Contracts
- Connect to the SCN and prepare the node environment for contract deployment. Clone the repository servicechain-value-transfer-examples.
In this step, we would deploy both the bridge contract and token contract in the parent as well as the child chain. Token contracts are for mint/transfer test and bridge contracts are used to listen/handle value transfer requests.
$ git clone https://github.com/klaytn/servicechain-value-transfer-examples$ cd servicechain-value-transfer-examples$ npm install$ cd erc20
On a text editor, edit the bridge_info.json
as below.
- Replace
url
in thechild
section (SCN node on ServiceChain network) with your SCN node IP and the proper port number fromRPC_PORT
inkscnd.conf
. - Replace
child.key
withtestkey1
that was generated byhomi
. - Set
child.operator
to thesubbridge.childOperator
address that we examined in the previous step. - Replace
url
in theparent
section (EN node on Kairos network) with your EN node IP and the proper port number fromRPC_PORT
inkend.conf
. - Replace
parent.key
with the private key of the test account created from https://toolkit.kaia.io/account/accountKeyLegacy in the previous step. - Set
parent.operator
as thesubbridge.parentOperator
of the previous step.
{ "child" : { "url": "http://192.168.0.1:7551", "key": "0x66cb283353589a10866b58d388e9d956e5a9c873a8c78fa4411d460c19c494ea", "operator": "0x10221f7f9355017cd0c11444e7eecb99621bacce" }, "parent" : { "url": "http://192.168.0.5:8551", "key": "0x26f4b5ac42ceabcfd3b23a991fdbfc792d10ce700a99582fdf9185a8f163b790", "operator": "0x3ce216beeafc62d20547376396e89528e1d778ca" } }
Perform the token deployment by running the command node erc20-deploy.js
. This script deploys both the bridge contract and the token contract, and it outputs API usage to initialize bridge pair.
$ node erc20-deploy.js------------------------- erc20-deploy START -------------------------> info.bridge: 0xEa024d8101E112330f2d7B1a7e7932034E206721> info.token: 0xbE641028610F628835C36F12bE62d54d74308D70> info.bridge: 0xA5af6Ffe13b367626B5AdF827DdE7438E3Db4463> info.token: 0x52F8Fa79Fa6D37b18b7AC8f9Ca835373f3C9270f> subbridge.registerBridge("0xEa024d8101E112330f2d7B1a7e7932034E206721", "0xA5af6Ffe13b367626B5AdF827DdE7438E3Db4463")> subbridge.subscribeBridge("0xEa024d8101E112330f2d7B1a7e7932034E206721", "0xA5af6Ffe13b367626B5AdF827DdE7438E3Db4463")> subbridge.registerToken("0xEa024d8101E112330f2d7B1a7e7932034E206721", "0xA5af6Ffe13b367626B5AdF827DdE7438E3Db4463", "0xbE641028610F628835C36F12bE62d54d74308D70", "0x52F8Fa79Fa6D37b18b7AC8f9Ca835373f3C9270f")------------------------- erc20-deploy END -------------------------
Step 3: Token transfer
Perform token transfer with the command node erc20-transfer-1step.js
. This one-step token transfer requires modification of an ERC-20 token implementation. If you don't want to modify the token contract or you have a token contract that is already deployed, please refer to ERC-20 Token Transfer (two-step).
$ node erc20-transfer-1step.js------------------------- erc20-transfer-1step START -------------------------alice balance: 0requestValueTransfer..alice balance: 100------------------------- erc20-transfer-1step END -------------------------
If the result is alice balance: 100
, then it has been executed successfully.
ERC-20 Token Transfer (two-step)
Run erc20-transfer-2step.js for the two-step transfer example. With this two-step token transfer example, unmodified ERC-20 token contracts can be used.
The two-step transfer consists of two function calls: (1) approve the bridge contract first, and then (2) call the contract function requestERC20Transfer()
.
We do not deploy contracts in this section since we already deployed both bridge and token contracts. You must deploy first if you didn't deploy them. You can deploy the contract using node erc20-deploy.js
.
$ node erc20-transfer-2step.js> ------------------------- erc20-transfer-2step START -------------------------> alice balance: 100> requestValueTransfer..> alice balance: 200------------------------- erc20-transfer-2step END -------------------------
KIP-7 Token Transfer via ERC-20 Interface (two-step)
KIP-7 is a token standard compatible with ERC-20. We can call requestERC20Transfer()
function to a KIP-7 token contract to transfer KIP-7 tokens between a parent chain and a child chain.
In the case of sending KIP-7 tokens via the ERC-20 interface, we call the approve()
function to allow the bridge to send the tokens on behalf of the transaction sender. Then call the requestERC20Transfer()
function.
The below command deploys the bridge contract and a KIP-7 contract.
$ node kip7-deploy.js> ------------------------- kip7-deploy START -------------------------> info.bridge: 0x04e929Cd2A08acd28a210369407D8Ca237Edd8FE> info.token: 0xE0E2fC6C7d1eB069153E0c12a4C87B01586b39e7> info.bridge: 0xEb502159A4B4E876B1cb423f250DCC0d276e01b6> info.token: 0xd4f02Ca1d49674056A9ec78fbBDc9e1e97726A4F> subbridge.registerBridge("0x04e929Cd2A08acd28a210369407D8Ca237Edd8FE", "0xEb502159A4B4E876B1cb423f250DCC0d276e01b6")> subbridge.subscribeBridge("0x04e929Cd2A08acd28a210369407D8Ca237Edd8FE", "0xEb502159A4B4E876B1cb423f250DCC0d276e01b6")> subbridge.registerToken("0x04e929Cd2A08acd28a210369407D8Ca237Edd8FE", "0xEb502159A4B4E876B1cb423f250DCC0d276e01b6", "0xE0E2fC6C7d1eB069153E0c12a4C87B01586b39e7", "0xd4f02Ca1d49674056A9ec78fbBDc9e1e97726A4F")------------------------- kip7-deploy END -------------------------
The below command is an example of sending KIP-7 tokens using the ERC-20 interface with requestERC20Transfer()
.
$ node kip7-transfer-2step-erc20-interface.js> ------------------------- kip7-transfer-2step-erc20-interface START -------------------------> alice balance: 0> requestValueTransfer..> alice balance: 100> ------------------------- kip7-transfer-2step-erc20-interface END -------------------------
Please refer service-chain-value-transfer-example for the other cases.
Native Support for KIP-7 and KIP-17 (To Be Implemented)
Currently, the bridge contract provided by the Kaia team supports only requestERC20Transfer()
and requestERC721Transfer()
for token transfer. The corresponding request functions for KIP-7 and KIP-17 will be supported soon. Before the implementation is done, as you can see above, you can transfer KIP-7 tokens using ERC-20 interfaces.
Value Transfer for ERC-721, KIP-17, and KAIA
The workflow for ERC-721, KIP-17, and KAIA is the same as above. erc721
, kip17
, and kaia
directories contain corresponding example source code.