}
// Compressed keys require you to know an extra bit of data about the y-coord as there are two possibilities.
// So it's encoded in the recId.
ECPoint R = decompressKey(x, (recId & 1) == 1);
// 1.4. If nR != point at infinity, then do another iteration of Step 1 (callers responsibility).
if (!R.multiply(n).isInfinity())
return null;
// 1.5. Compute e from M using Steps 2 and 3 of ECDSA signature verification.
BigInteger e = new BigInteger(1, messageHash);
// 1.6. For k from 1 to 2 do the following. (loop is outside this function via iterating recId)
// 1.6.1. Compute a candidate public key as: