Creating a Certificate in Java : Certificate « Security

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.security.KeyStore;

import java.security.PrivateKey;

import java.util.Date;



import sun.security.x509.AlgorithmId;

import sun.security.x509.CertificateAlgorithmId;

import sun.security.x509.CertificateIssuerName;

import sun.security.x509.CertificateSerialNumber;

import sun.security.x509.CertificateSubjectName;

import sun.security.x509.CertificateValidity;

import sun.security.x509.X500Name;

import sun.security.x509.X509CertImpl;

import sun.security.x509.X509CertInfo;



public class MainClass {

  public static void main(String[] args) throws Exception {

    String keystoreFile = "keyStoreFile.bin";

    String caAlias = "caAlias";

    String certToSignAlias = "cert";

    String newAlias = "newAlias";



    char[] password = new char[]{'a','b','c','d','e','f','g','h'};

    char[] caPassword = new char[]{'a','b','c','d','e','f','g','h'};

    char[] certPassword = new char[]{'a','b','c','d','e','f','g','h'};



    FileInputStream input = new FileInputStream(keystoreFile);

    KeyStore keyStore = KeyStore.getInstance("JKS");

    keyStore.load(input, password);

    input.close();



    PrivateKey caPrivateKey = (PrivateKey) keyStore.getKey(caAlias, caPassword);

    java.security.cert.Certificate caCert = keyStore.getCertificate(caAlias);



    byte[] encoded = caCert.getEncoded();

    X509CertImpl caCertImpl = new X509CertImpl(encoded);



    X509CertInfo caCertInfo = (X509CertInfo) caCertImpl.get(X509CertImpl.NAME + "."

        + X509CertImpl.INFO);



    X500Name issuer = (X500Name) caCertInfo.get(X509CertInfo.SUBJECT + "."

        + CertificateIssuerName.DN_NAME);



    java.security.cert.Certificate cert = keyStore.getCertificate(certToSignAlias);

    PrivateKey privateKey = (PrivateKey) keyStore.getKey(certToSignAlias, certPassword);

    encoded = cert.getEncoded();

    X509CertImpl certImpl = new X509CertImpl(encoded);

    X509CertInfo certInfo = (X509CertInfo) certImpl

        .get(X509CertImpl.NAME + "." + X509CertImpl.INFO);



    Date firstDate = new Date();

    Date lastDate = new Date(firstDate.getTime() + 365 * 24 * 60 * 60 * 1000L);

    CertificateValidity interval = new CertificateValidity(firstDate, lastDate);



    certInfo.set(X509CertInfo.VALIDITY, interval);



    certInfo.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber(

        (int) (firstDate.getTime() / 1000)));



    certInfo.set(X509CertInfo.ISSUER + "." + CertificateSubjectName.DN_NAME, issuer);



    AlgorithmId algorithm = new AlgorithmId(AlgorithmId.md5WithRSAEncryption_oid);

    certInfo.set(CertificateAlgorithmId.NAME + "." + CertificateAlgorithmId.ALGORITHM, algorithm);

    X509CertImpl newCert = new X509CertImpl(certInfo);



    newCert.sign(caPrivateKey, "MD5WithRSA");



    keyStore.setKeyEntry(newAlias, privateKey, certPassword,

        new java.security.cert.Certificate[] { newCert });



    FileOutputStream output = new FileOutputStream(keystoreFile);

    keyStore.store(output, password);

    output.close();



  }

}
Creating a Certificate in Java : Certificate « Security « Java Tutorial
