Named variables?

[julien51]

Hi!
I think your example is one of the clearest... Yet, it would be helpful if you used more descriptive variable names in the method signature ;)

[ppoliani]

There is currently an open issue regarding the documentation of ecrecover function. ethereum/solidity#681

However, you can look into the web3 docs for more details.

I can try to explain how it works:

Bob signs a hash of (contract_address, value): this can be done using the web3 helper function:

const h = web3.sha3(`${contract_address}${value}`);
const sig = web3.eth.sign(address, h);

Alice will get the sig and when she wants to close the channel she can send a transaction that will call the CloseChannel function of the smart contract. But she must first pass all the required parameters. That's actually quite simple if you have the sig:

 const r = `0x${sig.slice(0, 64)}`
 const s = `0x${sig.slice(64, 128)}`
 const v = web3.toDecimal(sig.slice(128, 130)) + 27

Then the smart contract can use ecrecover which as stated in the Solidity docs:

ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address):
recover the address associated with the public key from elliptic curve signature or return zero on error

The parameter names are kind of a convention when using ECDSA values.

[julien51]

Thanks a lot! this clarifies things a little bit...