Function secp256k1_sign_ecdsa_recoverable

pub fn secp256k1_sign_ecdsa_recoverable(
    input: &Bytes,
    gas_limit: u64,
) -> Result<PrecompileOutput, PrecompileErrors>

We give signing the same gas cost as Ethereum’s ecrecover precompile, which we expect is slightly conservative.

Recovering a public key from a signature requires one scalar inverse, an ecmult, a field square root, two scalar mul, and some other operations that take very little time relatively. Ecrecover must recover the public key, plus do some keccak hashing to recover the address. In comparision, signing is one scalar inverse, an ecmult, two scalar mul, and some other operations Notably, it does not require any square roots or keccak hashing, so it should be slight less gas-expensive.