สอบถามเรื่อง Encryption และ Decryption (Android) !!

    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;
    }
}

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) {
}

public class EncryptUtils {
   public static final String DEFAULT_ENCODING="UTF-8"; 
   static BASE64Encoder enc=new BASE64Encoder();
   static BASE64Decoder dec=new BASE64Decoder();

   public static String base64encode(String text){
      try {
         String rez = enc.encode( text.getBytes( DEFAULT_ENCODING ) );
         return rez;         
      }
      catch ( UnsupportedEncodingException e ) {
         return null;
      }
   }//base64encode

   public static String base64decode(String text){

         try {
            return new String(dec.decodeBuffer( text ),DEFAULT_ENCODING);
         }
         catch ( IOException e ) {
           return null;
         }

      }//base64decode

      public static void main(String[] args){
       String txt="some text to be encrypted" ;
       String key="key phrase used for XOR-ing";
       System.out.println(txt+" XOR-ed to: "+(txt=xorMessage( txt, key )));
       String encoded=base64encode( txt );       
       System.out.println( " is encoded to: "+encoded+" and that is decoding to: "+ (txt=base64decode( encoded )));
       System.out.print( "XOR-ing back to original: "+xorMessage( txt, key ) );

      }

      public static String xorMessage(String message, String key){
       try {
          if (message==null || key==null ) return null;

         char[] keys=key.toCharArray();
         char[] mesg=message.toCharArray();

         int ml=mesg.length;
         int kl=keys.length;
         char[] newmsg=new char[ml];

         for (int i=0; i<ml; i++){
            newmsg[i]=(char)(mesg[i]^keys[i%kl]);
         }//for i
         mesg=null; keys=null;
         return new String(newmsg);
      }
      catch ( Exception e ) {
         return null;
       }  
      }//xorMessage

}//class