DsaSignatureGenerator.java - Generating DSA Digital Signature

This section provides tutorial example on how to generate a digital signature for a message file with a DSA private key using the SHA1withDSA algorithm.

Here my DSA signature generation program, DsaSignatureGenerator.java, using the java.security.Signature class:

/**
 * DsaSignatureGenerator.java
#- Copyright (c) 2013, HerongYang.com, All Rights Reserved.
 */
import java.io.*;
import java.security.*;
import java.security.spec.*;
class DsaSignatureGenerator {
   public static void main(String[] a) {
      if (a.length<3) {
         System.out.println("Usage:");
         System.out.println("java DsaSignatureGenerator keyFile"
            + " msgFile sigFile");
         return;
      }
      String keyFile = a[0];
      String msgFile = a[1];
      String sigFile = a[2];
      String keyAlgo = "DSA";
      String sigAlgo = "SHA1withDSA";
      
      try {
         PrivateKey priKey = readPrivateKey(keyFile,keyAlgo);
         sign(msgFile,sigFile,sigAlgo,priKey);
      } catch (Exception e) {
         System.out.println("Exception: "+e);
         return;
      }
   }
   private static PrivateKey readPrivateKey(String input,
         String algorithm) throws Exception {
      KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
      FileInputStream priKeyStream = new FileInputStream(input);
      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());
      return priKey;
   }
   private static byte[] sign(String input, String output, 
      String algorithm, PrivateKey priKey) throws Exception {
      Signature sg = Signature.getInstance(algorithm);
      sg.initSign(priKey);
      System.out.println();
      System.out.println("Signature Object Info: ");
      System.out.println("Algorithm = "+sg.getAlgorithm());
      System.out.println("Provider = "+sg.getProvider());
      FileInputStream in = new FileInputStream(input);
      int bufSize = 1024;
      byte[] buffer = new byte[bufSize];
      int n = in.read(buffer,0,bufSize);
      int count = 0;
      while (n!=-1) {
         count += n;
         sg.update(buffer,0,n);
         n = in.read(buffer,0,bufSize);
      }
      in.close();
      FileOutputStream out = new FileOutputStream(output);
      byte[] sign = sg.sign();
      out.write(sign);
      out.close();
      System.out.println();
      System.out.println("Sign Processing Info: ");
      System.out.println("Number of input bytes = "+count);
      System.out.println("Number of output bytes = "+sign.length);
      return sign;
   }
}

Some notes on DsaSignatureGenerator.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

 DsaKeyGenerator.java - Generating DSA Key Pair

 DSA 512-bit and 1024-bit Key Pair Examples

 DsaKeyChecker.java - Reading and Checking DSA Keys

 Example of DSA Key Parameters and Properties

 java.security.Signature - The Data Signing Class

DsaSignatureGenerator.java - Generating DSA Digital Signature

 DsaSignatureGenerator.java Test Results

 DsaSignatureVerifier.java - Verifying DSA Digital Signature

 DsaSignatureVerifier.java Test Results

 Private key and Public Key Pair Generation

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

 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