code: public static ECKey signatureToKey(byte[] messageHash, ECDSASignature sig) throws SignatureException {
          final byte[] keyBytes = signatureToKeyBytes(messageHash, sig);
          return ECKey.fromPublicOnly(keyBytes);
      }
docs: Compute the key that signed the given signature.
  
  @param messageHash
  32-byte hash of message
  @param sig
  sig
  @return ECKey
  @throws SignatureException
  SignatureException