Difference between revisions of "Using the Java Cryptographic Extensions"

Revision as of 21:29, 27 May 2014

Note:

The code included in this article has not been reviewed and should not be used without proper analysis. If you have reviewed the included code (or portions of it), please post your findings back to this page or to: stephen [at] corsaire.com.

Overview

Java Cryptographic Extensions (JCE) is a set of Java API's which provides cryptographic services such as encryption, secret Key Generation, Message Authentication code and Key Agreement. The ciphers supported by JCE include symmetric, asymmetric, block and stream ciphers. JCE was an optional package to JDK v 1.2.x and 1.3.x. JCE has been integrated into JDK v1.4.

JCE API's are implemented by Cryptographic Service Providers. Each of these cryptographic service providers implements the Service Provider Interface which specifies the functionalities which needs to be implemented by the service providers. Programmers can plugin any Service Providers for performing cryptographic functionalities provided by JCE. J2SE comes with a default provider named SunJCE.

Symmetric Encryption Algorithms provided by SunJCE

1. DES - default keylength of 56 bits
2. AES -
3. RC2, RC4 and RC5
4. IDEA
5. Triple DES – default keylength 112 bits
6. Blowfish – default keylength 56 bits
7. PBEWithMD5AndDES
8. PBEWithHmacSHA1AndDESede
9. DES ede

Modes of Encryption

1. ECB
2. CBC
3. CFB
4. OFB
5. PCBC

Asymmetric Encryption Algorithms implemented by SunJCE

1. RSA
2. Diffie-Hellman – default keylength 1024 bits

Hashing / Message Digest Algorithms implemented by SunJCE

1. MD5 – default size 64 bytes
2. SHA1 - default size 64 bytes

Examples

SecureRandom

SecureRandom class is used to generate a cryptographically strong pseudo random number by using a PRNG Algorithm. The following are the advantages of using SecureRandom over Random. 1. SecureRandom produces a cryptographically strong pseudo random number generator. 2. SecureRandom produces cryptographically strong sequences as described in RFC 1750: Randomness Recommendations for Security

package org.owasp.java.crypto;

import java.security.SecureRandom;
import java.security.NoSuchAlgorithmException;

import sun.misc.BASE64Encoder;

/**
 * @author Joe Prasanna Kumar
 * This program provides the functionality for Generating a Secure Random Number.
 *  
 * There are 2 ways to generate a  Random number through SecureRandom.
 * 1. By calling nextBytes method to generate Random Bytes
 * 2. Using setSeed(byte[]) to reseed a Random object
 * 
 */


public class SecureRandomGen {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		try {
	        // Initialize a secure random number generator
	        SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
	    
	        // Method 1 - Calling nextBytes method to generate Random Bytes
	        byte[] bytes = new byte[512];
	        secureRandom.nextBytes(bytes); 
	        
	        // Printing the SecureRandom number by calling secureRandom.nextDouble()
	        System.out.println(" Secure Random # generated by calling nextBytes() is " + secureRandom.nextDouble());
	    
	        // Method 2 - Using setSeed(byte[]) to reseed a Random object
	        int seedByteCount = 10;
	        byte[] seed = secureRandom.generateSeed(seedByteCount);   
	        
	        // TBR System.out.println(" Seed value is " + new BASE64Encoder().encode(seed));
	    
	        secureRandom.setSeed(seed);
	        
	        System.out.println(" Secure Random # generated using setSeed(byte[]) is  " + secureRandom.nextDouble());
	        
	    } catch (NoSuchAlgorithmException noSuchAlgo)
		{
			System.out.println(" No Such Algorithm exists " + noSuchAlgo);
		}
	}

}

AES Encryption and Decryption

package org.owasp.java.crypto;

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.Cipher;

import java.security.NoSuchAlgorithmException;
import java.security.InvalidKeyException;
import java.security.InvalidAlgorithmParameterException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;

import sun.misc.BASE64Encoder;

/**
 * @author Joe Prasanna Kumar
 * This program provides the following cryptographic functionalities
 * 1. Encryption using AES
 * 2. Decryption using AES
 * 
 * High Level Algorithm :
 * 1. Generate a DES key (specify the Key size during this phase) 
 * 2. Create the Cipher 
 * 3. To Encrypt : Initialize the Cipher for Encryption
 * 4. To Decrypt : Initialize the Cipher for Decryption
 * 
 * 
 */

public class AES {
	public static void main(String[] args) {
		
		String strDataToEncrypt = new String();
		String strCipherText = new String();
		String strDecryptedText = new String();

		try {
			/**
			 * Step 1. Generate an AES key using KeyGenerator Initialize the
			 * keysize to 128 bits (16 bytes)
			 * 
			 */
			KeyGenerator keyGen = KeyGenerator.getInstance("AES");
			keyGen.init(128);
			SecretKey secretKey = keyGen.generateKey();

			/**
			 * Step 2. Generate an Initialization Vector (IV) 
			 * 		a. Use SecureRandom to generate random bits
			 * 		   The size of the IV matches the blocksize of the cipher (128 bits for AES)
			 * 		b. Construct the appropriate IvParameterSpec object for the data to pass to Cipher's init() method
			 */

			final int AES_KEYLENGTH = 128;	// change this as desired for the security level you want
			byte[] iv = new byte[AES_KEYLENGTH / 8];	// Save the IV bytes or send it in plaintext with the encrypted data so you can decrypt the data later
			SecureRandom prng = new SecureRandom();
			prng.nextBytes(iv);
			
			/**
			 * Step 3. Create a Cipher by specifying the following parameters
			 * 		a. Algorithm name - here it is AES 
			 * 		b. Mode - here it is CBC mode 
			 * 		c. Padding - e.g. PKCS7 or PKCS5
			 */

			Cipher aesCipherForEncryption = Cipher.getInstance("AES/CBC/PKCS7PADDING"); // Must specify the mode explicitly as most JCE providers default to ECB mode!!

			/**
			 * Step 4. Initialize the Cipher for Encryption
			 */

			aesCipherForEncryption.init(Cipher.ENCRYPT_MODE, secretKey, 
					new IvParameterSpec(iv));

			/**
			 * Step 5. Encrypt the Data 
			 * 		a. Declare / Initialize the Data. Here the data is of type String 
			 * 		b. Convert the Input Text to Bytes 
			 * 		c. Encrypt the bytes using doFinal method
			 */
			strDataToEncrypt = "Hello World of Encryption using AES ";
			byte[] byteDataToEncrypt = strDataToEncrypt.getBytes();
			byte[] byteCipherText = aesCipherForEncryption
					.doFinal(byteDataToEncrypt);
			// b64 is done differently on Android
			strCipherText = new BASE64Encoder().encode(byteCipherText);
			System.out.println("Cipher Text generated using AES is "
					+ strCipherText);

			/**
			 * Step 6. Decrypt the Data 
			 * 		a. Initialize a new instance of Cipher for Decryption (normally don't reuse the same object)
			 * 		   Be sure to obtain the same IV bytes for CBC mode.
			 * 		b. Decrypt the cipher bytes using doFinal method
			 */

			Cipher aesCipherForDecryption = Cipher.getInstance("AES/CBC/PKCS7PADDING"); // Must specify the mode explicitly as most JCE providers default to ECB mode!!				

			aesCipherForDecryption.init(Cipher.DECRYPT_MODE, secretKey,
					new IvParameterSpec(iv));
			byte[] byteDecryptedText = aesCipherForDecryption
					.doFinal(byteCipherText);
			strDecryptedText = new String(byteDecryptedText);
			System.out
					.println(" Decrypted Text message is " + strDecryptedText);
		}

		catch (NoSuchAlgorithmException noSuchAlgo) {
			System.out.println(" No Such Algorithm exists " + noSuchAlgo);
		}

		catch (NoSuchPaddingException noSuchPad) {
			System.out.println(" No Such Padding exists " + noSuchPad);
		}

		catch (InvalidKeyException invalidKey) {
			System.out.println(" Invalid Key " + invalidKey);
		}

		catch (BadPaddingException badPadding) {
			System.out.println(" Bad Padding " + badPadding);
		}

		catch (IllegalBlockSizeException illegalBlockSize) {
			System.out.println(" Illegal Block Size " + illegalBlockSize);
		}

		catch (InvalidAlgorithmParameterException invalidParam) {
			System.out.println(" Invalid Parameter " + invalidParam);
		}
	}
}

Des Encryption and Decryption

package org.owasp.crypto;

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.Cipher;

import java.security.NoSuchAlgorithmException;
import java.security.InvalidKeyException;
import java.security.InvalidAlgorithmParameterException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;

import sun.misc.BASE64Encoder;

/**
 * @author Joe Prasanna Kumar
 * This program provides the following cryptographic functionalities
 * 1. Encryption using DES
 * 2. Decryption using DES
 * 
 * The following modes of DES encryption are supported by SUNJce provider 
 * 1. ECB (Electronic code Book) - Every plaintext block is encrypted separately 
 * 2. CBC (Cipher Block Chaining) - Every plaintext block is XORed with the previous ciphertext block
 * 3. PCBC (Propogating Cipher Block Chaining) - 
 * 4. CFB (Cipher Feedback Mode) - The previous ciphertext block is encrypted and this enciphered block is XORed with the plaintext block to produce the corresponding ciphertext block 
 * 5. OFB (Output Feedback Mode) - 
 *
 *	High Level Algorithm :
 * 1. Generate a DES key
 * 2. Create the Cipher (Specify the Mode and Padding)
 * 3. To Encrypt : Initialize the Cipher for Encryption
 * 4. To Decrypt : Initialize the Cipher for Decryption
 * 
 * Need for Padding :
 * Block ciphers operates on data blocks on fixed size n. 
 * Since the data to be encrypted might not always be a multiple of n, the remainder of the bits are padded.
 * PKCS#5 Padding is what will be used in this program 
 * 
 */

public class DES {
	public static void main(String[] args) {
		
		String strDataToEncrypt = new String();
		String strCipherText = new String();
		String strDecryptedText = new String();
		
		try{
		/**
		 *  Step 1. Generate a DES key using KeyGenerator 
		 * 
		 */
		KeyGenerator keyGen = KeyGenerator.getInstance("DES");
		SecretKey secretKey = keyGen.generateKey();
		
		/**
		 *  Step2. Create a Cipher by specifying the following parameters
		 * 			a. Algorithm name - here it is DES
		 * 			b. Mode - here it is CBC
		 * 			c. Padding - PKCS5Padding
		 */
		
		Cipher desCipher = Cipher.getInstance("DES/CBC/PKCS5Padding"); /* Must specify the mode explicitly as most JCE providers default to ECB mode!! */
		
		/**
		 *  Step 3. Initialize the Cipher for Encryption 
		 */
		
		desCipher.init(Cipher.ENCRYPT_MODE,secretKey);
		
		/**
		 *  Step 4. Encrypt the Data
		 *  		1. Declare / Initialize the Data. Here the data is of type String
		 *  		2. Convert the Input Text to Bytes
		 *  		3. Encrypt the bytes using doFinal method 
		 */
		strDataToEncrypt = "Hello World of Encryption using DES ";
		byte[] byteDataToEncrypt = strDataToEncrypt.getBytes();
		byte[] byteCipherText = desCipher.doFinal(byteDataToEncrypt); 
		strCipherText = new BASE64Encoder().encode(byteCipherText);
		System.out.println("Cipher Text generated using DES with CBC mode and PKCS5 Padding is " +strCipherText);
		
		/**
		 *  Step 5. Decrypt the Data
		 *  		1. Initialize the Cipher for Decryption 
		 *  		2. Decrypt the cipher bytes using doFinal method 
		 */
		desCipher.init(Cipher.DECRYPT_MODE,secretKey,desCipher.getParameters());
		 //desCipher.init(Cipher.DECRYPT_MODE,secretKey);
		byte[] byteDecryptedText = desCipher.doFinal(byteCipherText);
		strDecryptedText = new String(byteDecryptedText);
		System.out.println(" Decrypted Text message is " +strDecryptedText);
		}
		
		catch (NoSuchAlgorithmException noSuchAlgo)
		{
			System.out.println(" No Such Algorithm exists " + noSuchAlgo);
		}
		
			catch (NoSuchPaddingException noSuchPad)
			{
				System.out.println(" No Such Padding exists " + noSuchPad);
			}
		
				catch (InvalidKeyException invalidKey)
				{
					System.out.println(" Invalid Key " + invalidKey);
				}
				
				catch (BadPaddingException badPadding)
				{
					System.out.println(" Bad Padding " + badPadding);
				}
				
				catch (IllegalBlockSizeException illegalBlockSize)
				{
					System.out.println(" Illegal Block Size " + illegalBlockSize);
				}
				
				catch (InvalidAlgorithmParameterException invalidParam)
				{
					System.out.println(" Invalid Parameter " + invalidParam);
				}
	}

}