With this example we are going to demonstrate how to encrypt/decrypt with DES using a password phrase. DES in computing refers to the Data Encryption Standard and is supported by Java. In short, to encrypt/decrypt with DES using a password phrase you should:
- Create a String password that can be used with password-based encryption (PBE).
- Provide password, salt, iteration count for generating PBEKey of fixed-key-size PBE Ciphers.
- Create a SecretKey using PBE with MD5 and DES.
- Construct a AlgorithmParameterSpec for password-based encryption as defined in the PKCS #5 standard.
- Initialize two Ciphers, one in encryption mode and the other one in decryption mode. Use them to encrypt the String message and then decrypt the encrypted String.
- The encryption is performed in the
String encrypt(String str)method. It encodes the string into a sequence of bytes using the named charset, storing the result into a new byte array. Then it callsdoFinal(byte[] input)API method of Cipher to make the encryption. It uses thecom.sun.mail.util.BASE64EncoderStreamto encode the encrypted byte array and returns the String created from the byte array. - The decryption is performed in the
String decrypt(String str)method. It uses thecom.sun.mail.util.BASE64DecoderStreamto decode the String to byte array. Then it callsdoFinal(byte[] input)API method of Cipher to make the decryption. It creates a new string based on the specified charset from the decrypted byte array. - You can handle exceptions like InvalidAlgorithmParameterException, InvalidKeySpecException, NoSuchAlgorithmException
InvalidAlgorithmParameterException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;
import com.sun.mail.util.BASE64DecoderStream;
import com.sun.mail.util.BASE64EncoderStream;
public class EncryptDecryptWithDESUsingPassPhrase {
private static Cipher ecipher;
private static Cipher dcipher;
private static final int iterationCount = 10;
// 8-byte Salt
private static byte[] salt = {
(byte)0xB2, (byte)0x12, (byte)0xD5, (byte)0xB2,
(byte)0x44, (byte)0x21, (byte)0xC3, (byte)0xC3
};
public static void main(String[] args) {
try {
String passPhrase = "My Secret Password";
// create a user-chosen password that can be used with password-based encryption (PBE)
// provide password, salt, iteration count for generating PBEKey of fixed-key-size PBE ciphers
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
// create a secret (symmetric) key using PBE with MD5 and DES
SecretKey key = SecretKeyFactory.getInstance("PBEWithMD5AndDES").generateSecret(keySpec);
// construct a parameter set for password-based encryption as defined in the PKCS #5 standard
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
ecipher = Cipher.getInstance(key.getAlgorithm());
dcipher = Cipher.getInstance(key.getAlgorithm());
// initialize the ciphers with the given key
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
String encrypted = encrypt("This is a classified message!");
String decrypted = decrypt(encrypted);
System.out.println("Decrypted: " + decrypted);
}
catch (InvalidAlgorithmParameterException e) {
System.out.println("Invalid Alogorithm Parameter:" + e.getMessage());
return;
}
catch (InvalidKeySpecException e) {
System.out.println("Invalid Key Spec:" + e.getMessage());
return;
}
catch (NoSuchAlgorithmException e) {
System.out.println("No Such Algorithm:" + e.getMessage());
return;
}
catch (NoSuchPaddingException e) {
System.out.println("No Such Padding:" + e.getMessage());
return;
}
catch (InvalidKeyException e) {
System.out.println("Invalid Key:" + e.getMessage());
return;
}
}
public static String encrypt(String str) {
try {
// encode the string into a sequence of bytes using the named charset
// storing the result into a new byte array.
byte[] utf8 = str.getBytes("UTF8");
byte[] enc = ecipher.doFinal(utf8);
// encode to base64
enc = BASE64EncoderStream.encode(enc);
return new String(enc);
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
public static String decrypt(String str) {
try {
// decode with base64 to get bytes
byte[] dec = BASE64DecoderStream.decode(str.getBytes());
byte[] utf8 = dcipher.doFinal(dec);
// create new string based on the specified charset
return new String(utf8, "UTF8");
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
}Output:
Decrypted: This is a classified message!
This was an example of how to encrypt/decrypt with DES using a password phrase in Java.
