How to implement AES technique for cryptography

Question

i want to implement the AES techniques in java for android application, i search out many tutorial for this but that was not super. SO please help in this regard, if some body know the code, for Implementing AES techniques for ANDROID APPLICATION. thanks in adnvance.

You just need to google http://stackoverflow.com/questions/6788018/android-encryption-decryption-with-aes — DjHacktorReborn, Mar 07 '13 at 18:49
@DjHacktorReborn for example if i would encrypt the world like "HELLO" the how can i implement it using AES, the link you referd was basis on image encryption/decryption — Fahim da UETIAN, Mar 07 '13 at 18:59
... really? What is the name of the application you're developing @MrMujahed? — Nik Bougalis, Mar 07 '13 at 19:09

score 2 · Accepted Answer · answered Mar 07 '13 at 19:06

Aes ecrpt class package com.d.social.network;

import java.security.NoSuchAlgorithmException;

    import javax.crypto.Cipher;
    import javax.crypto.NoSuchPaddingException;
    import javax.crypto.spec.IvParameterSpec;
    import javax.crypto.spec.SecretKeySpec;

    public class MCrypt {

        private String iv = "fedcba9876543210";//Dummy iv (CHANGE IT!)
        private IvParameterSpec ivspec;
        private SecretKeySpec keyspec;
        private Cipher cipher;

        private String SecretKey = "0123456789abcdef";//Dummy secretKey (CHANGE IT!)

        public MCrypt()
        {
            ivspec = new IvParameterSpec(iv.getBytes());

            keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");

            try {
                cipher = Cipher.getInstance("AES/CBC/NoPadding");
            } catch (NoSuchAlgorithmException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        public byte[] encrypt(String text) throws Exception
        {
            if(text == null || text.length() == 0)
                throw new Exception("Empty string");

            byte[] encrypted = null;

            try {
                cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);

                encrypted = cipher.doFinal(padString(text).getBytes());
            } catch (Exception e)
            {           
                throw new Exception("[encrypt] " + e.getMessage());
            }

            return encrypted;
        }

        public byte[] decrypt(String code) throws Exception
        {
            if(code == null || code.length() == 0)
                throw new Exception("Empty string");

            byte[] decrypted = null;


            try {
                cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);

                decrypted = cipher.doFinal(hexToBytes(code));
                if( decrypted.length > 0)
                {
                    int trim = 0;
                    for( int i = decrypted.length - 1; i >= 0; i-- ) if( decrypted[i] == 0 ) trim++;

                    if( trim > 0 )
                    {
                        byte[] newArray = new byte[decrypted.length - trim];
                        System.arraycopy(decrypted, 0, newArray, 0, decrypted.length - trim);
                        decrypted = newArray;
                    }
                }
            } catch (Exception e)
            {
                throw new Exception("[decrypt] " + e.getMessage());
            }
            return decrypted;
        }



        public static String bytesToHex(byte[] data)
        {
            if (data==null)
            {
                return null;
            }

            int len = data.length;
            String str = "";
            for (int i=0; i<len; i++) {
                if ((data[i]&0xFF)<16)
                    str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
                else
                    str = str + java.lang.Integer.toHexString(data[i]&0xFF);
            }
            return str;
        }


        public static byte[] hexToBytes(String str) {
            if (str==null) {
                return null;
            } else if (str.length() < 2) {
                return null;
            } else {
                int len = str.length() / 2;
                byte[] buffer = new byte[len];
                for (int i=0; i<len; i++) {
                    buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
                }
                return buffer;
            }
        }



        private static String padString(String source)
        {
          char paddingChar = ' ';
          int size = 16;
          int x = source.length() % size;
          int padLength = size - x;

          for (int i = 0; i < padLength; i++)
          {
              source += paddingChar;
          }

          return source;
        }
    }

To use it

MCrypt mcrypt = new MCrypt();
 MCrypt.bytesToHex( mcrypt.encrypt("hello"));

you are really a demon man, i like your job, a perfect and abrupt answer. Thank you, thank you and thank you... — Fahim da UETIAN, Mar 07 '13 at 19:17

How to implement AES technique for cryptography

1 Answers1