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

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