import java.security.PrivateKey;
import java.security.Signature;
import java.security.cert.Certificate;

public static byte[] make_signature(byte[] input_bytes, String signatureMethod, PrivateKey private_key, Certificate cert) throws Exception {
Signature sig = Signature.getInstance(signatureMethod);
sig.initSign(private_key);
sig.update(input_bytes);
byte[] signature_bytes = sig.sign();
return signature_bytes;
}