import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.SecureRandom;
import java.security.Security;
import java.security.Signature;
public class MainClass {
public static void main(String[] args) throws Exception {
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA", "BC");
keyGen.initialize(512, new SecureRandom());
KeyPair keyPair = keyGen.generateKeyPair();
Signature signature = Signature.getInstance("SHA1withRSA", "BC");
signature.initSign(keyPair.getPrivate(), new SecureRandom());
byte[] message = "abc".getBytes();
signature.update(message);
byte[] sigBytes = signature.sign();
signature.initVerify(keyPair.getPublic());
signature.update(message);
System.out.println(signature.verify(sigBytes));
}
}