How to get the zero address from ecrecover?

Question

I have a fair understanding of how ecrecover works, but I don't know how to enforce a parameter set that will deterministically return the 0x0 address. I need this in my contract tests.

Is this even possible?

Answer 1

I stumbled upon this thread, then I discovered this document and I now understand that setting v as any (positive?) number other than 27 or 28 will deterministically return 0x0 as the origin signer address.

Test it for yourself in solidity:

function getSignerZero(bytes32 msgHash, bytes32 r, bytes32 s) public returns (address _signer) {
    uint8 wrongV = 17; // should normally be 27 or 28
    return ecrecover(msgHash, wrongV, r, s);
}

Also, a caveat if you're using assembly and staticcall: it's actually incorrect to say that the value returned is 0x0. What happens there is that the precompile never gets back with a new value, so your program will just point to the same value it pointed before the call.