JcaKeyFactoryTest.java - Key Factory Test Program

This section provides a tutorial example on how to write a sample program to read encoded key files into key spec objects and convert them back into key objects.

The following sample program shows you how to use the KeyFactory class to read in encoded keys from files:

/**
 * JcaKeyFactoryTest.java
#- Copyright (c) 2013, HerongYang.com, All Rights Reserved.
 */
import java.io.*;
import java.math.*;
import java.security.*;
import java.security.interfaces.*;
import java.security.spec.*;
class JcaKeyFactoryTest {
   public static void main(String[] a) {
      if (a.length<3) {
         System.out.println("Usage:");
         System.out.println("java JcaKeyFactoryTest keySize output"
            +" algorithm");
         return;
      }
      int keySize = Integer.parseInt(a[0]);
      String output = a[1];
      String algorithm = a[2]; // RSA, DSA
      try {
         writeKeys(keySize,output,algorithm);
         readKeys(output,algorithm);
      } catch (Exception e) {
         System.out.println("Exception: "+e);
         return;
      }
   }
   private static void writeKeys(int keySize, String output, 
         String algorithm) throws Exception {
      KeyPairGenerator kg = KeyPairGenerator.getInstance(algorithm);
      kg.initialize(keySize);
      System.out.println();
      System.out.println("KeyPairGenerator Object Info: ");
      System.out.println("Algorithm = "+kg.getAlgorithm());
      System.out.println("Provider = "+kg.getProvider());
      System.out.println("Key Size = "+keySize);
      System.out.println("toString = "+kg.toString());
      KeyPair pair = kg.generateKeyPair();
      PrivateKey priKey = pair.getPrivate();
      PublicKey pubKey = pair.getPublic();

      String fl = output+".pri";
      FileOutputStream out = new FileOutputStream(fl);
      byte[] ky = priKey.getEncoded();
      out.write(ky);
      out.close();
      System.out.println();
      System.out.println("Private Key Info: ");
      System.out.println("Algorithm = "+priKey.getAlgorithm());
      System.out.println("Saved File = "+fl);
      System.out.println("Length = "+ky.length);
      System.out.println("Format = "+priKey.getFormat());
      System.out.println("toString = "+priKey.toString());

      fl = output+".pub";
      out = new FileOutputStream(fl);
      ky = pubKey.getEncoded();
      out.write(ky);
      out.close();
      System.out.println();
      System.out.println("Public Key Info: ");
      System.out.println("Algorithm = "+pubKey.getAlgorithm());
      System.out.println("Saved File = "+fl);
      System.out.println("Length = "+ky.length);
      System.out.println("Format = "+pubKey.getFormat());
      System.out.println("toString = "+pubKey.toString());
   }
   private static void readKeys(String input,
         String algorithm) throws Exception {
      KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
      System.out.println();
      System.out.println("KeyFactory Object Info: ");
      System.out.println("Algorithm = "+keyFactory.getAlgorithm());
      System.out.println("Provider = "+keyFactory.getProvider());
      System.out.println("toString = "+keyFactory.toString());

      String priKeyFile = input+".pri";
      FileInputStream priKeyStream = new FileInputStream(priKeyFile);
      int priKeyLength = priKeyStream.available();
      byte[] priKeyBytes = new byte[priKeyLength];
      priKeyStream.read(priKeyBytes);
      priKeyStream.close();
      PKCS8EncodedKeySpec priKeySpec 
         = new PKCS8EncodedKeySpec(priKeyBytes);
      PrivateKey priKey = keyFactory.generatePrivate(priKeySpec);
      System.out.println();
      System.out.println("Private Key Info: ");
      System.out.println("Algorithm = "+priKey.getAlgorithm());
      System.out.println("Saved File = "+priKeyFile);
      System.out.println("Length = "+priKeyBytes.length);
      System.out.println("toString = "+priKey.toString());

      String pubKeyFile = input+".pub";
      FileInputStream pubKeyStream = new FileInputStream(pubKeyFile);
      int pubKeyLength = pubKeyStream.available();
      byte[] pubKeyBytes = new byte[pubKeyLength];
      pubKeyStream.read(pubKeyBytes);
      pubKeyStream.close();
      X509EncodedKeySpec pubKeySpec 
         = new X509EncodedKeySpec(pubKeyBytes);
      PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);
      System.out.println();
      System.out.println("Public Key Info: ");
      System.out.println("Algorithm = "+pubKey.getAlgorithm());
      System.out.println("Saved File = "+pubKeyFile);
      System.out.println("Length = "+pubKeyBytes.length);
      System.out.println("toString = "+pubKey.toString());
   }
}

Note that:

See the next section for testing result of JcaKeyFactoryTest.java.

Last update: 2013.

Table of Contents

 About This Book

 Cryptography Terminology

 Cryptography Basic Concepts

 Introduction to AES (Advanced Encryption Standard)

 Introduction to DES Algorithm

 DES Algorithm - Illustrated with Java Programs

 DES Algorithm Java Implementation

 DES Algorithm - Java Implementation in JDK JCE

 DES Encryption Operation Modes

 DES in Stream Cipher Modes

 PHP Implementation of DES - mcrypt

 Blowfish - 8-Byte Block Cipher

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 Introduction of RSA Algorithm

 RSA Implementation using java.math.BigInteger Class

 Introduction of DSA (Digital Signature Algorithm)

 Java Default Implementation of DSA

 Private key and Public Key Pair Generation

PKCS#8/X.509 Private/Public Encoding Standards

 What Is Key Encoding?

 PKCS#8 and X.509 Key Encoding Classes

 java.security.KeyFactory - Reading Encoded Keys

JcaKeyFactoryTest.java - Key Factory Test Program

 Reading DSA Private and Public Key Files

 Reading RSA Private and Public Key Files

 Cipher - Public Key Encryption and Decryption

 MD5 Mesasge Digest Algorithm

 SHA1 Mesasge Digest Algorithm

 OpenSSL Introduction and Installation

 OpenSSL Generating and Managing RSA Keys

 OpenSSL Managing Certificates

 OpenSSL Generating and Signing CSR

 OpenSSL Validating Certificate Path

 "keytool" and "keystore" from JDK

 "OpenSSL" Signing CSR Generated by "keytool"

 Migrating Keys from "keystore" to "OpenSSL" Key Files

 Certificate X.509 Standard and DER/PEM Formats

 Migrating Keys from "OpenSSL" Key Files to "keystore"

 Using Certificates in IE (Internet Explorer)

 Using Certificates in Firefox

 Using Certificates in Google Chrome

 Outdated Tutorials

 References

 PDF Printing Version