How can I choose my own smart contract addresses on RSK before deploying it? - solidity

Question

I have noticed that some smart contracts
have addresses that start with 0x0000, 0x1234, or0x1337 - and I'm not sure how the deployers managed to do this.
​
Is it possible to do this on RSK?

Answer 1

Building upon the previous answer,
using the CREATE2 opcode -
it is not only possible to predict the address
that a smart contract will be deployed at,
but also (partially) choose the address
that you would like it to be deployed at.
For example, if you want a vanity address that starts
with 4 leading zeroes, you use the following helper function,
which checks for a match of the required vanity address:
function hasLeadingZeros(address = '0x0000', zeros = 4) {
for (let i = 2; i <= zeros + 1; i += 1) {
if (address.charAt(i) !== '0') return false;
}
return true;
}
The next helper function uses trial and error,
since keccak256 as with other hashes are 1-way functions,
to determine which salt parameter will result
in obtaining a required vanity address.
function getSaltForVanityAddress(deployerAddress, initCodeHash) {
let salt = 0;
let vanityAddress = '';
let saltHash;
while (!hasLeadingZeros(vanityAddress)) {
salt += 1;
saltHash = ethers.utils.keccak256(salt);
vanityAddress = ethers.utils.getCreate2Address(
deployerAddress,
saltHash,
initCodeHash,
);
}
return saltHash;
}
By combine the above, you can use
factory.deployCreate2(salt);
to deploy a smart contract with the address needed.
Here is a test case to illustrate:
it('Should deploy Child to the address starting with four zeros', async () => {
const Child = await ethers.getContractFactory('Child');
const { data: initCode } =
Child.getDeployTransaction(deployer.address);
const initCodeHash = ethers.utils.keccak256(initCode);
const salt = getSaltForVanityAddress(factory.address, initCodeHash);
const deployTx = await factory.deployCreate2(salt);
const txReceipt = await deployTx.wait();
const deployEvent = txReceipt.events.find(
(event) => event.event === 'ContractDeployed',
);
expect(hasLeadingZeros(
deployEvent.args.childContract)
).to.be.true;
console.log(
`Found salt '${salt}' such that the\ndeployed s/c address is ${deployEvent.args.childContract}`,
);
});
Found salt '0xb20ba450430132a5f0191bd27fc7e8018b39435484af81bbdf289296ae61ea75' such that the
deployed s/c address is 0x0000b36619Df7e2816577549b78CBB8b189e8d6B
✔ Should deploy Child to the address starting with four zeros (4973ms)