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) 2014, 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: 2014.

Table of Contents

 About This JDK Tutorial Book

 Downloading and Installing JDK 1.8.0 on Windows

 Downloading and Installing JDK 1.7.0 on Windows

 Downloading and Installing JDK 1.6.2 on Windows

 Java Date-Time API

 Date, Time and Calendar Classes

 Date and Time Object and String Conversion

 Number Object and Numeric String Conversion

 Locales, Localization Methods and Resource Bundles

 Calling and Importing Classes Defined in Unnamed Packages

 HashSet, Vector, HashMap and Collection Classes

 Character Set Encoding Classes and Methods

 Character Set Encoding Maps

 Encoding Conversion Programs for Encoded Text Files

 Socket Network Communication

 Datagram Network Communication

 DOM (Document Object Model) - API for XML Files

 SAX (Simple API for XML)

 DTD (Document Type Definition) - XML Validation

 XSD (XML Schema Definition) - XML Validation

 XSL (Extensible Stylesheet Language)

 Message Digest Algorithm Implementations in JDK

 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

 Digital Signature Algorithm and Sample Program

 "keytool" Commands and "keystore" Files

 KeyStore and Certificate Classes

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 The SSL (Secure Socket Layer) Protocol

 SSL Socket Communication Testing Programs

 SSL Client Authentication

 HTTPS (Hypertext Transfer Protocol Secure)

 Outdated Tutorials

 References

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