Creating a Self-Signed Version 1 Certificate : X509Certificate « Security « Java Tutorial

1. Java Tutorial
2. Security
3. X509Certificate

import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;
import java.security.SignatureException;
import java.security.cert.X509Certificate;
import java.util.Date;

import javax.security.auth.x500.X500Principal;

import org.bouncycastle.x509.X509V1CertificateGenerator;

public class MainClass {
  public static X509Certificate generateV1Certificate(KeyPair pair) throws InvalidKeyException,
      NoSuchProviderException, SignatureException {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

    X509V1CertificateGenerator certGen = new X509V1CertificateGenerator();

    certGen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis()));
    certGen.setIssuerDN(new X500Principal("CN=Test Certificate"));
    certGen.setNotBefore(new Date(System.currentTimeMillis() - 10000));
    certGen.setNotAfter(new Date(System.currentTimeMillis() + 10000));
    certGen.setSubjectDN(new X500Principal("CN=Test Certificate"));
    certGen.setPublicKey(pair.getPublic());
    certGen.setSignatureAlgorithm("SHA256WithRSAEncryption");

    return certGen.generateX509Certificate(pair.getPrivate(), "BC");
  }

  public static void main(String[] args) throws Exception {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
    KeyPair pair = generateRSAKeyPair();
    X509Certificate cert = generateV1Certificate(pair);
    cert.checkValidity(new Date());
    cert.verify(cert.getPublicKey());
  }

  public static KeyPair generateRSAKeyPair() throws Exception {
    KeyPairGenerator kpGen = KeyPairGenerator.getInstance("RSA", "BC");
    kpGen.initialize(1024, new SecureRandom());
    return kpGen.generateKeyPair();
  }
}