Encryption And Decryption Algorithm

How to write a code for encrypting and decrypting the password?

Encrypting a String with DES 

This example implements a class for encrypting and decrypting strings using DES. The class is created with a key and can be used repeatedly to encrypt and decrypt strings using that key. 

Code:

public class DesEncrypter {
    Cipher ecipher;
    Cipher dcipher;

    DesEncrypter(SecretKey key) {
        try {
            ecipher = Cipher.getInstance("DES");
            dcipher = Cipher.getInstance("DES");
            ecipher.init(Cipher.ENCRYPT_MODE, key);
            dcipher.init(Cipher.DECRYPT_MODE, key);

        } catch (javax.crypto.NoSuchPaddingException e) {
        } catch (java.security.NoSuchAlgorithmException e) {
        } catch (java.security.InvalidKeyException e) {
        }
    }

    public String encrypt(String str) {
        try {
            // Encode the string into bytes using utf-8
            byte[] utf8 = str.getBytes("UTF8");

            // Encrypt
            byte[] enc = ecipher.doFinal(utf8);

            // Encode bytes to base64 to get a string
            return new sun.misc.BASE64Encoder().encode(enc);
        } catch (javax.crypto.BadPaddingException e) {
        } catch (IllegalBlockSizeException e) {
        } catch (UnsupportedEncodingException e) {
        } catch (java.io.IOException e) {
        }
        return null;
    }

    public String decrypt(String str) {
        try {
            // Decode base64 to get bytes
            byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);

            // Decrypt
            byte[] utf8 = dcipher.doFinal(dec);

            // Decode using utf-8
            return new String(utf8, "UTF8");
        } catch (javax.crypto.BadPaddingException e) {
        } catch (IllegalBlockSizeException e) {
        } catch (UnsupportedEncodingException e) {
        } catch (java.io.IOException e) {
        }
        return null;
    }
}
 

Here's an example that uses the class: 

Code:

try {
    // Generate a temporary key. In practice, you would save this key.
    // See also Encrypting with DES Using a Pass Phrase.
    SecretKey key = KeyGenerator.getInstance("DES").generateKey();

    // Create encrypter/decrypter class
    DesEncrypter encrypter = new DesEncrypter(key);

    // Encrypt
    String encrypted = encrypter.encrypt("Don't tell anybody!");

    // Decrypt
    String decrypted = encrypter.decrypt(encrypted);
} catch (Exception e) {
}
 

Notes:

Add these import statements at the beginning to get it running.

import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.spec.*;
import java.io.*;

If you are using Eclipse do the following steps:

1. Open project properties.
2. Select Java Build Path node.
3. Select Libraries tab.
4. Remove JRE System Library.
5. Add Library JRE System Library.
6. Select workspace default library

Do you have a Java Problem?
Ask It in The Java Forum

Java Books
Java Certification, Programming, JavaBean and Object Oriented Reference Books

Return to : Java Programming Hints and Tips

All the site contents are Copyright © www.erpgreat.com and the content authors. All rights reserved.
All product names are trademarks of their respective companies.
The site www.erpgreat.com is not affiliated with or endorsed by any company listed at this site.
Every effort is made to ensure the content integrity.  Information used on this site is at your own risk.
 The content on this site may not be reproduced or redistributed without the express written permission of
www.erpgreat.com or the content authors.