Wednesday, July 30, 2014

AES Implementation In Java with ECB | CBC | OFB | CFB Modes Of Operation

Note that these are ONLY basic level programs for easy understanding of the Advanced Encryption Standard (AES) algorithm

Key Generation - AESkeygen.java
 
import java.io.File;
import java.io.FileWriter;

public class AESkeygen {
 
 private final File file = new File("AESkey.txt");
 private final int KEY_LENGTH = 32;
 private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
 
 public AESkeygen() {
  try {   
   FileWriter fileWriter = new FileWriter(file);
   fileWriter.write("");
   for (int i = 0 ; i < KEY_LENGTH ; i++) {
    double random = Math.random();
    int index = (int) (random * 16);
    fileWriter.append(hexArray[index]);
    fileWriter.flush();
   }
   fileWriter.close();
   System.out.println("Key generated and saved in " + file.getName());
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }
 
 public static void main(String[] args) {
  new AESkeygen();
 }

}


Word.java
 

public class Word {
 
 private byte[] word = null;
 
 public Word() {
  word = new byte[4];
 }
 
 public Word(byte k0, byte k1, byte k2, byte k3) {
  this();
  word[0] = k0;
  word[1] = k1;
  word[2] = k2;
  word[3] = k3;
 }
 
 public byte[] getWord() {
  return word;
 }
 
 public void setWord(byte[] word) {
  this.word = word;
 }
 
 public static byte[] wordToBytes(Word word) {
  return word.getWord();
 }
 
 public static byte[] wordsToBytes(Word[] words) {
  byte[] out = new byte[4 * words.length];
  for (int i = 0 ; i < words.length ; i++) {
   byte[] temp = words[i].getWord();
   out[4*i] = temp[0];
   out[4*i+1] = temp[1];
   out[4*i+2] = temp[2];
   out[4*i+3] = temp[3];   
  }
  return out;
 }
 
 public void rotWord() {
  byte[] temp = this.getWord();
  byte[] newWord = new byte[4];
  newWord[0] = temp[1];
  newWord[1] = temp[2];
  newWord[2] = temp[3];
  newWord[3] = temp[0]; 
  this.setWord(newWord);
 }
 
 public void subWord() {
  byte[] in = this.getWord();
  byte[] out = new byte[4];  
  for (int i = 0 ; i < 4 ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) AESencrypt.sBox[row * 16 + col];
  }
  for (int i = 0 ; i < 4 ; i++) {
   this.word[i] = out[i];
  }  
 } 
 
 public static Word XORWords(Word word1, Word word2) {
  Word outWord = new Word();
  byte[] in1 = word1.getWord();
  byte[] in2 = word2.getWord();
  byte[] out = new byte[4];
  for (int i = 0 ; i < 4 ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }
  outWord.setWord(out);  
  return outWord;
 }
 
 public String toString() {
  return AESencrypt.bytesToHex(this.getWord());
 }
}


Encryption - AESencrypt.java
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.util.Arrays;

public class AESencrypt {
 
 private static final int BITS = 16;
 private static final int ROUNDS = 10;
 private static final int NO_OF_WORDS_IN_KEY = 44;
 private static final int KEY_LENGTH = 16;
 private static final int BLOCK_LENGTH = 16;
 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
 int[] RC = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36};
 Word[] Rcon = new Word[ROUNDS]; 
 private byte[] word = null;
 private String mode = null;
 
 static final int[] sBox = {
  0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
 };
  
 static final int[] invSBox = {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 
  0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 
  0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 
  0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 
  0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 
  0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 
  0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 
  0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 
  0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 
  0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 
  0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 
  0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 
  0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
 };
  
 
 public AESencrypt(String mode) {
  this.mode = mode;
  for (int i = 0 ; i < ROUNDS ; i++) {
   Rcon[i] = new Word();
   byte[] temp = new byte[4];
   temp[0] = (byte) (RC[i] & 0xff);
   temp[1] = 0;
   temp[2] = 0;
   temp[3] = 0;
   Rcon[i].setWord(temp);   
  }
  word = new byte[NO_OF_WORDS_IN_KEY];
 }
 
 /* Ref: http://www.samiam.org/galois.html */
 /* Galois Addition*/
 byte gadd(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Subtraction*/
 byte gsub(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Multiplication*/
 byte gmul(byte a, byte b) {
  byte p = 0;
  int counter;
  byte high_bit_set;
  byte byte0x80 = hexStringToByteArray("80")[0];
  for (counter = 0 ; counter < 8 ; counter++) {
   if((b & 0x01) == 1) {
    //System.out.println("lower bit of b is set");
    p = (byte)((p ^ a) & 0xff);
   }   
   high_bit_set = (byte) (a & 0x80);
   //printByte("high_bit_set", high_bit_set);
   a <<= 1;
   if (high_bit_set == byte0x80) {
    //System.out.println("higher bit of a is set");
    a = (byte)((a ^ 0x1b) & 0xff);
   }
   b = (byte)((b >> 1) & 0x7f);
   
   //printByte("a", a);
   //printByte("b", b);
   //printByte("p", p);
  }
  return p;
 }
 
 byte gmul(byte a, int b) {
  byte t = (byte)(b & 0xff);
  return gmul(a, t);
 }
 
 /* Key Expansion */
 private byte[] expandKey(byte[] key) throws Exception {
  //System.out.println(key.length);
  //System.out.println(bytesToHex(key));
  if(key.length != KEY_LENGTH) {
   throw new Exception("Key should be of length, 128 bits");
  }
  Word[] w = new Word[NO_OF_WORDS_IN_KEY]; 
  Word temp;
  for (int i = 0; i < 4; i++) {
   w[i] = new Word(key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]); 
   //System.out.println("w" + i + " = " + w[i]);
  }
  
  for (int i = 4; i < 44; i++) {
   temp = w[i-1];
   Word temp1 = new Word();
   temp1.setWord(temp.getWord());
   //System.out.println("w" + (i-1) + " = " + temp);
   if (i % 4 == 0) {
    temp1.rotWord();
    //System.out.println("Rot=" + temp1);
    temp1.subWord();
    //System.out.println("Sub=" + temp1);
    temp1 = Word.XORWords(temp1, Rcon[(i/4) - 1]);
    //System.out.println("Rcon" + temp1);
   }
   w[i] = Word.XORWords(w[i-4], temp1);
   //System.out.println("w" + i + " = " + w[i]);   
  }
  return Word.wordsToBytes(w);
 }
 
 /* Substitute Bytes */
 private byte[] subBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) sBox[row * BITS + col];
  }
  return out;
 }
 
 /* Inverse Substitute Bytes */
 private byte[] inverseSubBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) invSBox[row * BITS + col];
  }
  return out;
 }
 
 /* Shift Rows */
 private byte[] shiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  //System.out.println("temp: " + bytesToHex(temp));
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = leftShift(a, i);
   in[4*i] = b[0];
   in[4*i+1] = b[1];
   in[4*i+2] = b[2];
   in[4*i+3] = b[3];
  }   
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] leftShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[1];
   out[1] = in[2];
   out[2] = in[3];
   out[3] = in[0];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Inverse Shift Rows */
 private byte[] inverseShiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = rightShift(a, i);
   in[4 * i] = b[0];
   in[4 * i + 1] = b[1];
   in[4 * i + 2] = b[2];
   in[4 * i + 3] = b[3];
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] rightShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[3];
   out[1] = in[0];
   out[2] = in[1];
   out[3] = in[2];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Mix Columns */
 private byte[] mixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 2)  ^ gmul(in[4*1+j], 3)  ^ in[4*2+j]    ^ in[4*3+j])    & 0xff);
   out[4*1+j] = (byte) ((in[4*0+j]    ^ gmul(in[4*1+j], 2)  ^ gmul(in[4*2+j], 3)  ^ in[4*3+j])    & 0xff);
   out[4*2+j] = (byte) ((in[4*0+j]    ^ in[4*1+j]    ^ gmul(in[4*2+j], 2)  ^ gmul(in[4*3+j], 3))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 3)  ^ in[4*1+j]    ^ in[4*2+j]    ^ gmul(in[4*3+j], 2))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 /* Inverse Mix Columns */
 private byte[] inverseMixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 14)  ^ gmul(in[4*1+j], 11)  ^ gmul(in[4*2+j], 13)  ^ gmul(in[4*3+j], 9))  & 0xff);
   out[4*1+j] = (byte) ((gmul(in[4*0+j], 9)  ^ gmul(in[4*1+j], 14)  ^ gmul(in[4*2+j], 11)  ^ gmul(in[4*3+j], 13))  & 0xff);
   out[4*2+j] = (byte) ((gmul(in[4*0+j], 13)  ^ gmul(in[4*1+j], 9) ^ gmul(in[4*2+j], 14)  ^ gmul(in[4*3+j], 11))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 11)  ^ gmul(in[4*1+j], 13) ^ gmul(in[4*2+j], 9) ^ gmul(in[4*3+j], 14))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 private byte[] hexStringToByteArray(String string) {
  int length = string.length();
  int n = (int)Math.ceil((length + 1) / 2);
  byte[] result = new byte[n];  
  for (int i = length - 1; i >= 0 ; i -= 2) { 
   if (i == 0) {
    result[i / 2] = (byte) ((Character.digit('0', 16) << 4)
      + Character.digit(string.charAt(i), 16));
   } else {
    result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4)
     + Character.digit(string.charAt(i), 16));
   }
  }
  return result;
 }
 
 /* http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java */
 public static String bytesToHex(byte[] bytes) {
     char[] hexChars = new char[bytes.length * 2];
     for ( int j = 0; j < bytes.length; j++ ) {
         int v = bytes[j] & 0xFF;
         hexChars[j * 2] = hexArray[v >>> 4];
         hexChars[j * 2 + 1] = hexArray[v & 0x0F];
     }
     return new String(hexChars);
 }
 
 private void printBytes(byte[] input) {    
  for (int i = 0 ; i < input.length; i++) {
   System.out.print(byteToBits(input[i]) + " ");
  }
  System.out.println();
 }
 
 private void printByte(String msg, byte input) {
  byte[] temp = new byte[1];
  temp[0] = input;
  System.out.println(msg + ": " + bytesToHex(temp));  
 }
 
 private String byteToBits(byte b) {
  StringBuffer buffer = new StringBuffer();
  for (int i = 0 ; i < 8 ; i++)
   buffer.append((int)(b >> (8-(i+1)) & 0x0001));
  return buffer.toString();
 }
 
 private byte[] getRoundKey(int round) {
  byte[] out = new byte[KEY_LENGTH];
  out = Arrays.copyOfRange(word, 16*round, 16*round+16);  
  return out;
 }
 
 public static byte[] XORBytes(byte[] in1, byte[] in2) {  
  byte[] out = new byte[in1.length];
  for (int i = 0 ; i < in1.length ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }   
  return out;
 }
 
 public byte[] encryptText(byte[] plainText, byte[] key) throws Exception {
  byte[] cipher = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(0);
  /* Round 0 */
  cipher = XORBytes(plainText, roundKey);
  //System.out.println("Round 0\n" + bytesToHex(cipher));
  /* Rounds 1 to 9*/
  for (int i = 1 ; i < 10 ; i++) {
   //System.out.println("Round " + i);
   cipher = subBytes(cipher);
   //System.out.println("SubBytes: " + bytesToHex(cipher));
   cipher = shiftRows(cipher);
   //System.out.println("ShiftRows: " + bytesToHex(cipher));
   cipher = mixColumns(cipher);
   //System.out.println("MixColumns: " + bytesToHex(cipher));
   roundKey = getRoundKey(i);
   //System.out.println("RoundKey: " + bytesToHex(roundKey));
   cipher = XORBytes(cipher, roundKey);   
   //System.out.println("CIPHER: " + bytesToHex(cipher));
  }
  /* Round 10*/
  //System.out.println("Round 10");
  cipher = subBytes(cipher);
  //System.out.println("SubBytes: " + bytesToHex(cipher));
  cipher = shiftRows(cipher);
  //System.out.println("ShiftRows: " + bytesToHex(cipher));
  roundKey = getRoundKey(10);
  //System.out.println("RoundKey: " + bytesToHex(roundKey));
  cipher = XORBytes(cipher, roundKey);
  //System.out.println("CIPHER: " + bytesToHex(cipher));
  return cipher;
 }
 
 public byte[] decryptText(byte[] cipher, byte[] key) throws Exception {
  byte[] plainText = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(10);
  /* Round 0 */
  plainText = XORBytes(cipher, roundKey);
  /* Rounds 1 to 9*/
  for (int i = 9 ; i > 0 ; i--) {
   plainText = inverseShiftRows(plainText);
   plainText = inverseSubBytes(plainText);
   roundKey = getRoundKey(i);
   plainText = XORBytes(plainText, roundKey);
   plainText = inverseMixColumns(plainText);
  }
  /* Round 10*/
  plainText = inverseShiftRows(plainText);
  plainText = inverseSubBytes(plainText);
  roundKey = getRoundKey(0);
  plainText = XORBytes(plainText, roundKey);
  return plainText;
 }
 
 public static void main(String[] args) throws Exception {
  try {
   if (args.length != 1) {
    System.out.println("Usage: java < classname > < mode >"
      + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
    return;
   }
   /* ECB, CBC, OFB, or CFB */   
   String mode = args[0];
   //String mode = "CFB";
   mode = mode.toUpperCase();
   AESencrypt aes = new AESencrypt(mode); 
   File keyFile = new File("AESkey.txt");
   File textFile = new File("AESplaintext.txt");
   File cipherFile = new File("AESciphertext.txt");   
   FileReader keyFileReader = new FileReader(keyFile);
   BufferedReader bufferedReader = new BufferedReader(keyFileReader);
   FileInputStream textFileInputStream = new FileInputStream(textFile);
   FileOutputStream cipherFileOutputStream = new FileOutputStream(cipherFile);
   byte[] key = new byte[(int) keyFile.length()];
   String keyString = bufferedReader.readLine();
   key = aes.hexStringToByteArray(keyString);
   byte[] message = new byte[(int) textFile.length()];
   textFileInputStream.read(message);        
   byte[] cipher = aes.encrypt(message, key);
   cipherFileOutputStream.write(cipher);
   cipherFileOutputStream.flush();
   cipherFileOutputStream.close();
   bufferedReader.close();
   textFileInputStream.close();
   System.out.println("Encryption done! Please check AESciphertext.txt for output!");
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }

 private byte[] encrypt(byte[] message, byte[] key) throws Exception {
  if (message.length < 16) {
   System.out.println("Message should be atleast 64 bits");
   System.exit(1);
  }
  if (key.length != 16) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  int length = message.length;
  int n = (length + 15)/16 * 16;
  byte[] cipher = new byte[n];
  if (length == 16) {
   if (mode.equals("ECB")) {
    return encryptText(message, key);
   } else if (mode.equals("CBC")) {
    byte[] iv = getInitializationVector();
    message = XORBytes(message, iv);
    return encryptText(message, key);
   } else if (mode.equals("OFB")) {
    byte[] nounce = getNounce();
    byte[] temp = encryptText(nounce, key);
    byte[] result = XORBytes(temp, message);
    return result;
   } else if (mode.equals("CFB")) {
    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
  }
  int i = 0;
  int k = 0;
  byte[] feedback = new byte[16];  
  if (mode.equals("CBC")) {
   feedback = getInitializationVector();
  } else if (mode.equals("OFB")) {
   feedback = getNounce();   
  } else if (mode.equals("CFB")) {
   feedback = getInitializationVectorCFB();
  }
  
  while (i < length) {
   byte[] block = new byte[16];
   byte[] result = new byte[16];
   int j = 0;
   for (; j < 16 && i < length; j++, i++) {
    block[j] = message[i];
   }
   while (j < 16) {
    /* pad with white spaces */
    block[j++] = 0x20;
   }
      
   //System.out.println("BLOCK: ");
   //printBytes(block);  
   if (mode.equals("ECB")) {
    result = encryptText(block, key);
   } else if (mode.equals("CBC")) {    
    block = XORBytes(block, feedback);
    result = encryptText(block, key);
    feedback = Arrays.copyOfRange(result, 0, 16);       
   } else if (mode.equals("OFB")) {
    result = encryptText(feedback, key);
    feedback = Arrays.copyOfRange(result, 0, 16);
    result = XORBytes(result, block);
   } else if (mode.equals("CFB")) {    
    result = encryptText(feedback, key);
    byte[] resultPart = Arrays.copyOfRange(result, 0, 8);
    byte[] blockPart = Arrays.copyOfRange(block, 0, 8);
    byte[] temp1 = XORBytes(resultPart, blockPart);
    feedback = mergeBytes(Arrays.copyOfRange(result, 8, 16), temp1);     
    resultPart = Arrays.copyOfRange(result, 8, 16);
    blockPart = Arrays.copyOfRange(block, 8, 16);
    result = encryptText(feedback, key);
    byte[] temp2 = XORBytes(resultPart, blockPart);
    feedback = mergeBytes(Arrays.copyOfRange(result, 8, 16), temp2);
    result = mergeBytes(temp1, temp2);       
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
   //System.out.println("RESULT: ");
   //printBytes(result);
   for (j = 0 ; j < 16 && k < cipher.length; j++, k++) {
    cipher[k] = result[j];
   }
  }
  return cipher;  
 }
 
 private byte[] getInitializationVector() {
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");   
 }
 
 private byte[] getInitializationVectorCFB() {
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");   
 }
 
 private byte[] getNounce() {
//  char[] hexArray = "0123456789ABCDEF".toCharArray();
//  String nounceStr = "";
//  for (int i = 0 ; i < 16 ; i++) {
//   double random = Math.random();
//   int index = (int) (random * 16);
//   nounceStr += hexArray[index];   
//  }
//  return hexStringToByteArray(nounceStr);
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");
 } 

 private byte[] mergeBytes(byte[] in1, byte[] in2) {
  byte[] out = new byte[in1.length + in2.length];
  int i = 0;
  for (int j = 0 ; j < in1.length ; j++) {
   out[i++] = in1[j];
  }
  for (int j = 0 ; j < in2.length ; j++) {
   out[i++] = in2[j];
  }
  return out;
 } 
}

Decryption - AESdecrypt.java
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.util.Arrays;

public class AESdecrypt {
 
 private static final int BITS = 16;
 private static final int ROUNDS = 10;
 private static final int NO_OF_WORDS_IN_KEY = 44;
 private static final int KEY_LENGTH = 16;
 private static final int BLOCK_LENGTH = 16;
 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
 int[] RC = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36};
 Word[] Rcon = new Word[ROUNDS]; 
 private byte[] word = null;
 private String mode = null;
 
 static final int[] sBox = {
  0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
 };
  
 static final int[] invSBox = {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 
  0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 
  0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 
  0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 
  0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 
  0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 
  0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 
  0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 
  0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 
  0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 
  0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 
  0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 
  0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
 };
  
 
 public AESdecrypt(String mode) {
  this.mode = mode;
  for (int i = 0 ; i < ROUNDS ; i++) {
   Rcon[i] = new Word();
   byte[] temp = new byte[4];
   temp[0] = (byte) (RC[i] & 0xff);
   temp[1] = 0;
   temp[2] = 0;
   temp[3] = 0;
   Rcon[i].setWord(temp);   
  }
  word = new byte[NO_OF_WORDS_IN_KEY];
 }
 
 /* Ref: http://www.samiam.org/galois.html */
 /* Galois Addition*/
 byte gadd(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Subtraction*/
 byte gsub(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Multiplication*/
 byte gmul(byte a, byte b) {
  byte p = 0;
  int counter;
  byte high_bit_set;
  byte byte0x80 = hexStringToByteArray("80")[0];
  for (counter = 0 ; counter < 8 ; counter++) {
   if((b & 0x01) == 1) {
    //System.out.println("lower bit of b is set");
    p = (byte)((p ^ a) & 0xff);
   }   
   high_bit_set = (byte) (a & 0x80);
   //printByte("high_bit_set", high_bit_set);
   a <<= 1;
   if (high_bit_set == byte0x80) {
    //System.out.println("higher bit of a is set");
    a = (byte)((a ^ 0x1b) & 0xff);
   }
   b = (byte)((b >> 1) & 0x7f);
   
   //printByte("a", a);
   //printByte("b", b);
   //printByte("p", p);
  }
  return p;
 }
 
 byte gmul(byte a, int b) {
  byte t = (byte)(b & 0xff);
  return gmul(a, t);
 }
 
 /* Key Expansion */
 private byte[] expandKey(byte[] key) throws Exception {
  //System.out.println(key.length);
  //System.out.println(bytesToHex(key));
  if(key.length != KEY_LENGTH) {
   throw new Exception("Key should be of length, 128 bits");
  }
  Word[] w = new Word[NO_OF_WORDS_IN_KEY]; 
  Word temp;
  for (int i = 0; i < 4; i++) {
   w[i] = new Word(key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]); 
   //System.out.println("w" + i + " = " + w[i]);
  }
  
  for (int i = 4; i < 44; i++) {
   temp = w[i-1];
   Word temp1 = new Word();
   temp1.setWord(temp.getWord());
   //System.out.println("w" + (i-1) + " = " + temp);
   if (i % 4 == 0) {
    temp1.rotWord();
    //System.out.println("Rot=" + temp1);
    temp1.subWord();
    //System.out.println("Sub=" + temp1);
    temp1 = Word.XORWords(temp1, Rcon[(i/4) - 1]);
    //System.out.println("Rcon" + temp1);
   }
   w[i] = Word.XORWords(w[i-4], temp1);
   //System.out.println("w" + i + " = " + w[i]);   
  }
  return Word.wordsToBytes(w);
 }
 
 /* Substitute Bytes */
 private byte[] subBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) sBox[row * BITS + col];
  }
  return out;
 }
 
 /* Inverse Substitute Bytes */
 private byte[] inverseSubBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) invSBox[row * BITS + col];
  }
  return out;
 }
 
 /* Shift Rows */
 private byte[] shiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  //System.out.println("temp: " + bytesToHex(temp));
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = leftShift(a, i);
   in[4*i] = b[0];
   in[4*i+1] = b[1];
   in[4*i+2] = b[2];
   in[4*i+3] = b[3];
  }   
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] leftShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[1];
   out[1] = in[2];
   out[2] = in[3];
   out[3] = in[0];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Inverse Shift Rows */
 private byte[] inverseShiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = rightShift(a, i);
   in[4 * i] = b[0];
   in[4 * i + 1] = b[1];
   in[4 * i + 2] = b[2];
   in[4 * i + 3] = b[3];
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] rightShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[3];
   out[1] = in[0];
   out[2] = in[1];
   out[3] = in[2];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Mix Columns */
 private byte[] mixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 2)  ^ gmul(in[4*1+j], 3)  ^ in[4*2+j]    ^ in[4*3+j])    & 0xff);
   out[4*1+j] = (byte) ((in[4*0+j]    ^ gmul(in[4*1+j], 2)  ^ gmul(in[4*2+j], 3)  ^ in[4*3+j])    & 0xff);
   out[4*2+j] = (byte) ((in[4*0+j]    ^ in[4*1+j]    ^ gmul(in[4*2+j], 2)  ^ gmul(in[4*3+j], 3))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 3)  ^ in[4*1+j]    ^ in[4*2+j]    ^ gmul(in[4*3+j], 2))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 /* Inverse Mix Columns */
 private byte[] inverseMixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 14)  ^ gmul(in[4*1+j], 11)  ^ gmul(in[4*2+j], 13)  ^ gmul(in[4*3+j], 9))  & 0xff);
   out[4*1+j] = (byte) ((gmul(in[4*0+j], 9)  ^ gmul(in[4*1+j], 14)  ^ gmul(in[4*2+j], 11)  ^ gmul(in[4*3+j], 13))  & 0xff);
   out[4*2+j] = (byte) ((gmul(in[4*0+j], 13)  ^ gmul(in[4*1+j], 9) ^ gmul(in[4*2+j], 14)  ^ gmul(in[4*3+j], 11))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 11)  ^ gmul(in[4*1+j], 13) ^ gmul(in[4*2+j], 9) ^ gmul(in[4*3+j], 14))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 private byte[] hexStringToByteArray(String string) {
  int length = string.length();
  int n = (int)Math.ceil((length + 1) / 2);
  byte[] result = new byte[n];  
  for (int i = length - 1; i >= 0 ; i -= 2) { 
   if (i == 0) {
    result[i / 2] = (byte) ((Character.digit('0', 16) << 4)
      + Character.digit(string.charAt(i), 16));
   } else {
    result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4)
     + Character.digit(string.charAt(i), 16));
   }
  }
  return result;
 }
 
 /* http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java */
 public static String bytesToHex(byte[] bytes) {
     char[] hexChars = new char[bytes.length * 2];
     for ( int j = 0; j < bytes.length; j++ ) {
         int v = bytes[j] & 0xFF;
         hexChars[j * 2] = hexArray[v >>> 4];
         hexChars[j * 2 + 1] = hexArray[v & 0x0F];
     }
     return new String(hexChars);
 }
 
 private void printBytes(byte[] input) {    
  for (int i = 0 ; i < input.length; i++) {
   System.out.print(byteToBits(input[i]) + " ");
  }
  System.out.println();
 }
 
 private void printByte(String msg, byte input) {
  byte[] temp = new byte[1];
  temp[0] = input;
  System.out.println(msg + ": " + bytesToHex(temp));  
 }
 
 private String byteToBits(byte b) {
  StringBuffer buffer = new StringBuffer();
  for (int i = 0 ; i < 8 ; i++)
   buffer.append((int)(b >> (8-(i+1)) & 0x0001));
  return buffer.toString();
 }
 
 private byte[] getRoundKey(int round) {
  byte[] out = new byte[KEY_LENGTH];
  out = Arrays.copyOfRange(word, 16*round, 16*round+16);  
  return out;
 }
 
 public static byte[] XORBytes(byte[] in1, byte[] in2) {  
  byte[] out = new byte[in1.length];
  for (int i = 0 ; i < in1.length ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);   
  }   
  return out;
 }
 
 public byte[] encryptText(byte[] plainText, byte[] key) throws Exception {
  byte[] cipher = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(0);
  /* Round 0 */
  cipher = XORBytes(plainText, roundKey);
  //System.out.println("Round 0\n" + bytesToHex(cipher));
  /* Rounds 1 to 9*/
  for (int i = 1 ; i < 10 ; i++) {
   //System.out.println("Round " + i);
   cipher = subBytes(cipher);
   //System.out.println("SubBytes: " + bytesToHex(cipher));
   cipher = shiftRows(cipher);
   //System.out.println("ShiftRows: " + bytesToHex(cipher));
   cipher = mixColumns(cipher);
   //System.out.println("MixColumns: " + bytesToHex(cipher));
   roundKey = getRoundKey(i);
   //System.out.println("RoundKey: " + bytesToHex(roundKey));
   cipher = XORBytes(cipher, roundKey);   
   //System.out.println("CIPHER: " + bytesToHex(cipher));
  }
  /* Round 10*/
  //System.out.println("Round 10");
  cipher = subBytes(cipher);
  //System.out.println("SubBytes: " + bytesToHex(cipher));
  cipher = shiftRows(cipher);
  //System.out.println("ShiftRows: " + bytesToHex(cipher));
  roundKey = getRoundKey(10);
  //System.out.println("RoundKey: " + bytesToHex(roundKey));
  cipher = XORBytes(cipher, roundKey);
  //System.out.println("CIPHER: " + bytesToHex(cipher));
  return cipher;
 }
 
 public byte[] decryptText(byte[] cipher, byte[] key) throws Exception {
  byte[] plainText = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(10);
  /* Round 0 */
  plainText = XORBytes(cipher, roundKey);
  /* Rounds 1 to 9*/
  for (int i = 9 ; i > 0 ; i--) {
   plainText = inverseShiftRows(plainText);
   plainText = inverseSubBytes(plainText);
   roundKey = getRoundKey(i);
   plainText = XORBytes(plainText, roundKey);
   plainText = inverseMixColumns(plainText);
  }
  /* Round 10*/
  plainText = inverseShiftRows(plainText);
  plainText = inverseSubBytes(plainText);
  roundKey = getRoundKey(0);
  plainText = XORBytes(plainText, roundKey);
  return plainText;
 }
 
 public static void main(String[] args) throws Exception {
  try {
   if (args.length != 1) {
    System.out.println("Usage: java < classname > < mode >"
      + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
    return;
   }
   /* ECB, CBC, OFB, or CFB */
   String mode = args[0];
   //String mode = "CFB";
   mode = mode.toUpperCase();
   AESdecrypt aes = new AESdecrypt(mode); 
   File keyFile = new File("AESkey.txt");
   File textFile = new File("AESplaintext.txt");
   File cipherFile = new File("AESciphertext.txt");   
   FileReader keyFileReader = new FileReader(keyFile);
   BufferedReader bufferedReader = new BufferedReader(keyFileReader);
   FileInputStream cipherFileInputStream = new FileInputStream(cipherFile);
   FileOutputStream textFileOutputStream = new FileOutputStream(textFile);
   byte[] key = new byte[(int) keyFile.length()];
   String keyString = bufferedReader.readLine();
   key = aes.hexStringToByteArray(keyString);
   byte[] cipher = new byte[(int) cipherFile.length()];
   cipherFileInputStream.read(cipher);        
   byte[] message = aes.decrypt(cipher, key);   
   textFileOutputStream.write(message);
   textFileOutputStream.flush();
   textFileOutputStream.close();
   bufferedReader.close();
   cipherFileInputStream.close();
   System.out.println("Decryption done! Please check AESplaintext.txt for output!");
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }

 private byte[] decrypt(byte[] message, byte[] key) throws Exception {
  if (message.length < 16) {
   System.out.println("Message should be atleast 64 bits");
   System.exit(1);
  }
  if (key.length != 16) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  int length = message.length;
  int n = (length + 15)/16 * 16;
  byte[] cipher = new byte[n];
  if (length == 16) {
   if (mode.equals("ECB")) {
    return decryptText(message, key);
   } else if (mode.equals("CBC")) {
    byte[] iv = getInitializationVector();
    message = XORBytes(message, iv);
    return decryptText(message, key);
   } else if (mode.equals("OFB")) {
    byte[] nounce = getNounce();
    byte[] temp = encryptText(nounce, key);
    byte[] result = XORBytes(temp, message);
    return result;
   } else if (mode.equals("CFB")) {
    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
  }
  int i = 0;
  int k = 0;
  byte[] feedback = new byte[16];  
  if (mode.equals("CBC")) {
   feedback = getInitializationVector();
  } else if (mode.equals("OFB")) {
   feedback = getNounce();   
  } else if (mode.equals("CFB")) {
   feedback = getInitializationVectorCFB();
  }
  
  while (i < length) {
   byte[] block = new byte[16];
   byte[] result = new byte[16];
   int j = 0;
   for (; j < 16 && i < length; j++, i++) {
    block[j] = message[i];
   }
   while (j < 16) {
    /* pad with white spaces */
    block[j++] = 0x20;
   }
      
   //System.out.println("BLOCK: ");
   //printBytes(block);  
   if (mode.equals("ECB")) {
    result = decryptText(block, key);
   } else if (mode.equals("CBC")) {    
    result = decryptText(block, key);
    result = XORBytes(result, feedback);
    feedback = Arrays.copyOfRange(block, 0, 16);     
   } else if (mode.equals("OFB")) {
    result = encryptText(feedback, key);
    feedback = Arrays.copyOfRange(result, 0, 16);
    result = XORBytes(result, block);    
   } else if (mode.equals("CFB")) {    
    result = encryptText(feedback, key);
    byte[] resultPart = Arrays.copyOfRange(result, 0, 8);
    byte[] blockPart = Arrays.copyOfRange(block, 0, 8);
    byte[] temp1 = XORBytes(resultPart, blockPart);
    feedback = mergeBytes(Arrays.copyOfRange(result, 8, 16), blockPart);     
    resultPart = Arrays.copyOfRange(result, 8, 16);
    blockPart = Arrays.copyOfRange(block, 8, 16);
    result = encryptText(feedback, key);
    byte[] temp2 = XORBytes(resultPart, blockPart);
    feedback = mergeBytes(Arrays.copyOfRange(result, 8, 16), blockPart);
    result = mergeBytes(temp1, temp2);
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
   //System.out.println("RESULT: ");
   //printBytes(result);
   for (j = 0 ; j < 16 && k < cipher.length; j++, k++) {
    cipher[k] = result[j];
   }
  }
  return cipher;  
 }
 
 private byte[] getInitializationVector() {
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");   
 }
 
 private byte[] getInitializationVectorCFB() {
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");   
 }
 
 private byte[] getNounce() {
//  char[] hexArray = "0123456789ABCDEF".toCharArray();
//  String nounceStr = "";
//  for (int i = 0 ; i < 16 ; i++) {
//   double random = Math.random();
//   int index = (int) (random * 16);
//   nounceStr += hexArray[index];   
//  }
//  return hexStringToByteArray(nounceStr);
  return hexStringToByteArray("247D8AC4DDB1AA739DC593821D0BC432");
 } 

 private byte[] mergeBytes(byte[] in1, byte[] in2) {
  byte[] out = new byte[in1.length + in2.length];
  int i = 0;
  for (int j = 0 ; j < in1.length ; j++) {
   out[i++] = in1[j];
  }
  for (int j = 0 ; j < in2.length ; j++) {
   out[i++] = in2[j];
  }
  return out;
 } 
}

Output
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESkeygen 
Key generated and saved in AESkey.txt 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt 
Usage: java < classname > < mode > 
 < mode > := (ECB|CBC|OFB|CFB) 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt ecb 
Encryption done! Please check AESciphertext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt ecb 
Decryption done! Please check AESplaintext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt cbc 
Encryption done! Please check AESciphertext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt cbc 
Decryption done! Please check AESplaintext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt ofb 
Encryption done! Please check AESciphertext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt ofb 
Decryption done! Please check AESplaintext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt cfb 
Encryption done! Please check AESciphertext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt cfb 
Decryption done! Please check AESplaintext.txt for output! 
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$

About Input/Output Files
AESkeygen.java - (output) AESkey.txt
AESencrypt.java - (input) AESkey.txt & AESplaintext.txt (output) AESciphertext.txt
AESdecrypt.java - (input) AESkey.txt & AESciphertext.txt (output) AESplaintext.txt

DES Implementation In Java with ECB | CBC | OFB | CFB Modes Of Operation

Note that these are ONLY basic level programs for easy understanding of the Data Encryption Standard (DES) algorithm

Key Generation - DESkeygen.java
 
import java.io.File;
import java.io.FileWriter;

public class DESkeygen {
 
 private final File file = new File("DESkey.txt");
 private final int KEY_LENGTH = 16;
 private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
 
 public DESkeygen() {
  try {   
   FileWriter fileWriter = new FileWriter(file);
   fileWriter.write("");
   for (int i = 0 ; i < KEY_LENGTH ; i++) {
    double random = Math.random();
    int index = (int) (random * 16);
    fileWriter.append(hexArray[index]);
    fileWriter.flush();
   }
   fileWriter.close();
   System.out.println("Key generated and saved in " + file.getName());
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }
 
 public static void main(String[] args) {
  new DESkeygen();
 }

}

Encryption - DESencrypt.java
 
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Arrays;


public class DESencrypt {
 
 private String mode = null;
 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
 
 /* Initial Permutation */
 static final int[] IP = {
  58, 50, 42, 34, 26, 18, 10, 2,
  60, 52, 44, 36, 28, 20, 12, 4,
  62, 54, 46, 38, 30, 22, 14, 6,
  64, 56, 48, 40, 32, 24, 16, 8,
  57, 49, 41, 33, 25, 17,  9, 1,
  59, 51, 43, 35, 27, 19, 11, 3,
  61, 53, 45, 37, 29, 21, 13, 5,
  63, 55, 47, 39, 31, 23, 15, 7
 };
 /* Inverse Initial Permutation */
 static final int[] IIP = {
  40, 8, 48, 16, 56, 24, 64, 32,
  39, 7, 47, 15, 55, 23, 63, 31,
  38, 6, 46, 14, 54, 22, 62, 30,
  37, 5, 45, 13, 53, 21, 61, 29,
  36, 4, 44, 12, 52, 20, 60, 28,
  35, 3, 43, 11, 51, 19, 59, 27,
  34, 2, 42, 10, 50, 18, 58, 26,
  33, 1, 41,  9, 49, 17, 57, 25
 };
 /* Expansion Permutation */
 static final int[] E = {
  32,  1,  2,  3,  4,  5,
  4,  5,  6,  7,  8,  9,
  8,  9, 10, 11, 12, 13,
  12, 13, 14, 15, 16, 17,
  16, 17, 18, 19, 20, 21,
  20, 21, 22, 23, 24, 25,
  24, 25, 26, 27, 28, 29,
  28, 29, 30, 31, 32,  1
 };
 /* Permutation Function */
 static final int[] P = {
  16,  7, 20, 21,
  29, 12, 28, 17,
  1, 15, 23, 26,
  5, 18, 31, 10,
  2,  8, 24, 14,
  32, 27,  3,  9,
  19, 13, 30,  6,
  22, 11,  4, 25
 };
 /* S-Boxes*/
 static final int[] S1 = {
  14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
   0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
   4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
  15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
 };
 static final int[] S2 = {
  15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
   3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
   0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
  13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
 };
 static final int[] S3 = {
  10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
  13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
  13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
   1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
 };
 static final int[] S4 = {
   7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
  13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
  10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
   3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
 };
 static final int[] S5 = {
   2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
  14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
   4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
  11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
 };
 static final int[] S6 = {
  12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
  10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
   9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
   4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
 };
 static final int[] S7 = {
   4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
  13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
   1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
   6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
 };
 static final int[] S8 = {
  13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
   1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
   7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
   2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
 };
 /* Permuted Choice One */
 static final int[] PC1 = {
  57, 49, 41, 33, 25, 17,  9,
   1, 58, 50, 42, 34, 26, 18,
  10,  2, 59, 51, 43, 35, 27,
  19, 11,  3, 60, 52, 44, 36,
  63, 55, 47, 39, 31, 23, 15,
   7, 62, 54, 46, 38, 30, 22,
  14,  6, 61, 53, 45, 37, 29,
  21, 13,  5, 28, 20, 12,  4
 };
 /* Permuted Choice Two */
 static final int[] PC2 = {
  14, 17, 11, 24,  1,  5,
   3, 28, 15,  6, 21, 10,
  23, 19, 12,  4, 26,  8,
  16,  7, 27, 20, 13,  2,
  41, 52, 31, 37, 47, 55,
  30, 40, 51, 45, 33, 48,
  44, 49, 39, 56, 34, 53,
  46, 42, 50, 36, 29, 32
 };
 /* Schedule of Left Shifts */
 static final int[] SHIFTS = {
  1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
 };
 
 public DESencrypt() {
  this.mode = "ECB";
 }
 
 public DESencrypt(String mode) {
  this.mode = mode;
 }
 
 private byte[] performXOR(byte[] one, byte[] two) {
  byte[] result = new byte[one.length];
  for (int i = 0 ; i < one.length ; i++) {
   result[i] = (byte) (one[i] ^ two[i]);
  }
  return result;
 }
 
 private byte[] permute(byte[] input, int[] mapping) {
  int byteCount = 1 + (mapping.length - 1) / 8;
  byte[] output = new byte[byteCount];
  int pos;
  
  for (int i = 0 ; i < mapping.length ; i++) {
   pos = mapping[i] - 1;
   int value = getBitFromArray(input, pos);
   setBitInArray(output, i, value);
  }  
  return output;
 } 

 private int getBitFromArray(byte[] array, int pos) {
  int value;
  int bytePos = pos / 8;
  int bitPos = pos % 8;  
  value = (array[bytePos] >> (8 - (bitPos + 1))) & 0x0001;  
  /* eg: right shift selected byte 5 times to get 3rd bit 
   * (bitPos = 2) at rightmost position and 
   * then AND with 0x0001*/
  return value;
 }
 
 private void setBitInArray(byte[] input, int pos, int value) {
  int bytePos = pos / 8;
  int bitPos = pos % 8;  
  byte old = input[bytePos];
  old = (byte) (((0xFF7F >> bitPos) & old) & 0x00FF);
  byte newByte = (byte) ((value << (8 - (bitPos + 1))) | old);
     input[bytePos] = newByte;
 }
 
 private byte[] hexStringToByteArray(String string) {
  int length = string.length();
  int n = (int)Math.ceil((length + 1) / 2);
  byte[] result = new byte[n];  
  for (int i = length - 1; i >= 0 ; i -= 2) { 
   if (i == 0) {
    result[i / 2] = (byte) ((Character.digit('0', 16) << 4)
      + Character.digit(string.charAt(i), 16));
   } else {
    result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4)
     + Character.digit(string.charAt(i), 16));
   }
  }
  return result;
 }
 
 public static String bytesToHex(byte[] bytes) {
     char[] hexChars = new char[bytes.length * 2];
     for ( int j = 0; j < bytes.length; j++ ) {
         int v = bytes[j] & 0xFF;
         hexChars[j * 2] = hexArray[v >>> 4];
         hexChars[j * 2 + 1] = hexArray[v & 0x0F];
     }
     return new String(hexChars);
 }
 
 private void printBytes(byte[] input) {    
  for (int i = 0 ; i < input.length; i++) {
   System.out.print(byteToBits(input[i]) + " ");
  }
  System.out.println();
 }
 
 private String byteToBits(byte b) {
  StringBuffer buffer = new StringBuffer();
  for (int i = 0 ; i < 8 ; i++)
   buffer.append((int)(b >> (8-(i+1)) & 0x0001));
  return buffer.toString();
 }

 private byte[] getBits(byte[] input, int startPos, int length) {
  int noOfBytes = (length-1)/8 + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < length ; i++) {
   int value = getBitFromArray(input, startPos + i);
   setBitInArray(output, i, value);
  }
  return output;
 } 
 
 private byte[] rotateLeft(byte[] input, int step, int length) {  
  int noOfBytes = (length - 1) / 8 + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < length ; i++) {
   int value = getBitFromArray(input, (i + step) % length);
   setBitInArray(output, i, value);
  }
  return output;
 }
 
 private byte[] concatBits(byte[] one, int oneLength, 
   byte[] two, int twoLength) {
  int noOfBytes = (oneLength + twoLength - 1) / 8 + 1;
  byte[] output = new byte[noOfBytes];
  int i = 0, j = 0;
  for (; i < oneLength ; i++) {
   int value = getBitFromArray(one, i);
   setBitInArray(output, j, value);
   j++;
  }  
  for (i = 0 ; i < twoLength ; i++) {
   int value = getBitFromArray(two, i);
   setBitInArray(output, j, value);
   j++;
  }
  return output;
 }
 
 private byte[][] getSubKeys(byte[] masterKey) {
  int noOfSubKeys = SHIFTS.length;
  int keySize = PC1.length;
  byte[] key = permute(masterKey, PC1);
  byte[][] subKeys = new byte[noOfSubKeys][keySize];
  byte[] leftHalf = getBits(key, 0, keySize/2);
  byte[] rightHalf = getBits(key, keySize/2, keySize/2);
  for (int i = 0 ; i < noOfSubKeys ; i++) {
   leftHalf = rotateLeft(leftHalf, SHIFTS[i], keySize/2);
   rightHalf = rotateLeft(rightHalf, SHIFTS[i], keySize/2);
   byte[] subKey = concatBits(leftHalf, keySize/2, rightHalf, keySize/2);
   subKeys[i] = permute(subKey, PC2); 
  }
  return subKeys;
 }
 
 public byte[] crypt(byte[] message, byte[] key, String operation) {
  if (message.length < 8) {
   System.out.println("Message should be atleast 64 bits");
   System.exit(1);
  }
  if (key.length != 8) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  int length = message.length;
  int n = (length + 7)/8 * 8;
  byte[] cipher = new byte[n];
  if (length == 8) {
   if (mode.equals("ECB")) {
    return cryptText(message, key, operation);
   } else if (mode.equals("CBC")) {
    byte[] iv = getInitializationVector();
    message = XORBytes(message, iv);
    return cryptText(message, key, operation);
   } else if (mode.equals("OFB")) {
    byte[] nounce = getNounce();
    byte[] temp = cryptText(nounce, key, operation);
    byte[] result = XORBytes(temp, message);
    return result;
   } else if (mode.equals("CFB")) {
    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
  }
  int i = 0;
  int k = 0;
  byte[] feedback = new byte[8];  
  if (mode.equals("CBC")) {
   feedback = getInitializationVector();
  } else if (mode.equals("OFB")) {
   feedback = getNounce();   
  } else if (mode.equals("CFB")) {
   feedback = getInitializationVectorCFB();
  }
  
  while (i < length) {
   byte[] block = new byte[8];
   byte[] result = new byte[8];
   int j = 0;
   for (; j < 8 && i < length; j++, i++) {
    block[j] = message[i];
   }
   while (j < 8) {
    /* pad with white spaces */
    block[j++] = 0x20;
   }
      
   //System.out.println("BLOCK: ");
   //printBytes(block);  
   if (mode.equals("ECB")) {
    result = cryptText(block, key, operation);
   } else if (mode.equals("CBC")) {
    if (operation.equals("encrypt")) {
     block = XORBytes(block, feedback);
     result = cryptText(block, key, operation);
     feedback = Arrays.copyOfRange(result, 0, 8);
    } else if (operation.equals("decrypt")) {
     result = cryptText(block, key, operation);
     result = XORBytes(result, feedback);
     feedback = Arrays.copyOfRange(block, 0, 8);
    }    
   } else if (mode.equals("OFB")) {
    result = cryptText(feedback, key, operation);
    feedback = Arrays.copyOfRange(result, 0, 8);
    result = XORBytes(result, block);    
   } else if (mode.equals("CFB")) {
    if (operation.equals("encrypt")) {
     result = cryptText(feedback, key, operation);
     byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
     byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
     byte[] temp1 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp1);     
     resultPart = Arrays.copyOfRange(result, 4, 8);
     blockPart = Arrays.copyOfRange(block, 4, 8);
     result = cryptText(feedback, key, operation);
     byte[] temp2 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp2);
     result = mergeBytes(temp1, temp2);
    } else if (operation.equals("decrypt")) {
     result = cryptText(feedback, key, "encrypt");
     byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
     byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
     byte[] temp1 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);     
     resultPart = Arrays.copyOfRange(result, 4, 8);
     blockPart = Arrays.copyOfRange(block, 4, 8);
     result = cryptText(feedback, key, "encrypt");
     byte[] temp2 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
     result = mergeBytes(temp1, temp2);
    }    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
   //System.out.println("RESULT: ");
   //printBytes(result);
   for (j = 0 ; j < 8 && k < cipher.length; j++, k++) {
    cipher[k] = result[j];
   }
  }
  return cipher;  
 }
 
 private byte[] getInitializationVector() {
  return hexStringToByteArray("DCBE6AE7EA5D5C61");   
 }
 
 private byte[] getInitializationVectorCFB() {
  return hexStringToByteArray("A5D5C61EFADB4351");   
 }
 
 private byte[] getNounce() {
//  char[] hexArray = "0123456789ABCDEF".toCharArray();
//  String nounceStr = "";
//  for (int i = 0 ; i < 16 ; i++) {
//   double random = Math.random();
//   int index = (int) (random * 16);
//   nounceStr += hexArray[index];   
//  }
//  return hexStringToByteArray(nounceStr);
  return hexStringToByteArray("DCBE6AE7EA5D5C61");
 } 

 private byte[] mergeBytes(byte[] in1, byte[] in2) {
  byte[] out = new byte[in1.length + in2.length];
  int i = 0;
  for (int j = 0 ; j < in1.length ; j++) {
   out[i++] = in1[j];
  }
  for (int j = 0 ; j < in2.length ; j++) {
   out[i++] = in2[j];
  }
  return out;
 }
 public byte[] cryptText(byte[] message, byte[] key, String operation) {
  if (message.length != 8) {
   System.out.println("Message should be 64 bits");
   System.exit(1);
  }
  if (key.length != 8) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  byte[] result = null;
  int blockSize = IP.length;
  byte[][] subKeys = getSubKeys(key);
  int noOfRounds = subKeys.length;
  /**
   * Initial Permutation
   */
  message = permute(message, IP);
  /**
   * Split message into two halves
   */
  byte[] leftHalf = getBits(message, 0, blockSize/2);
  byte[] rightHalf = getBits(message, blockSize/2, blockSize/2);
  for (int i = 0 ; i < noOfRounds ; i++) {
   byte[] temp = rightHalf;
   /**
    * Expansion
    */
   rightHalf = permute(rightHalf, E);
   /**
    * XOR rightHalf with roundKey
    */
   byte[] roundKey = null;
   if (operation.equalsIgnoreCase("encrypt")) {
    roundKey = subKeys[i];
   } else if (operation.equalsIgnoreCase("decrypt")) {
    roundKey = subKeys[noOfRounds - i - 1];
   } else {
    System.out.println("Unsupported operation");
    System.exit(0);
   }
   rightHalf = performXOR(rightHalf, roundKey);
   /**
    * S-Box
    */
   rightHalf = sBox(rightHalf);
   /**
    * Permutation
    */
   rightHalf = permute(rightHalf, P);
   /**
    * XOR rightHalf with leftHalf
    */
   rightHalf = performXOR(rightHalf, leftHalf);
   /**
    * L(i) = R(i-1)
    */
   leftHalf = temp;
  }
  /**
   * 32 bit swap
   */
  byte[] concatHalves = concatBits(rightHalf, blockSize/2, leftHalf, blockSize/2);
  /**
   * Inverse Initial Permutation
   */
  result = permute(concatHalves, IIP);
  return result;
 }
 
 public static byte[] XORBytes(byte[] in1, byte[] in2) {  
  byte[] out = new byte[in1.length];
  for (int i = 0 ; i < in1.length ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }
  return out;
 }
 
 private byte[] sBox(byte[] input) {  
  /**
   * Split input to 6-bit blocks
   */
  input = split(input,6);
  byte[] output = new byte[input.length/2];
  int leftHalf = 0;  
  for (int i = 0; i < input.length ; i++) {
   byte block = input[i];   
   /**
    * row - first and last bits
    * column - 4 bits in the middle
    */
   int row = 2 * (block >> 7 & 0x0001) + (block >> 2 & 0x0001);
   int col = block >> 3 & 0x000F;
   int[] selectedSBox = getSBox(i);
   int rightHalf = selectedSBox[16 * row + col];
   if (i % 2 == 0) {
    leftHalf = rightHalf;
   } else {
    output[i/2] = (byte) (16 * leftHalf + rightHalf);
    leftHalf = 0;
   }
  }
  return output;
 }

 private int[] getSBox(int i) {
  switch (i) {
   case 0: return S1;
   case 1: return S2;
   case 2: return S3;
   case 3: return S4;
   case 4: return S5;
   case 5: return S6;
   case 6: return S7;
   case 7: return S8; 
   default: return null;   
  }
 }

 private byte[] split(byte[] input, int length) {
  int noOfBytes = (8 * input.length - 1) / length + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < noOfBytes ; i++) {
   for (int j = 0; j < length ; j++) {
    int value = getBitFromArray(input, length * i + j);    
    setBitInArray(output, 8 * i + j, value);
   }
  }
  return output;
 }

 public static void main(String[] args) {
  try {
   if (args.length != 1) {
    System.out.println("Usage: java < classname > < mode >"
      + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
    return;
   }
   /* ECB, CBC, OFB, or CFB */   
   String mode = args[0];
   mode = mode.toUpperCase();
   DESencrypt des = new DESencrypt(mode); 
   File keyFile = new File("DESkey.txt");
   File textFile = new File("DESplaintext.txt");
   File cipherFile = new File("DESciphertext.txt");   
   FileReader keyFileReader = new FileReader(keyFile);
   BufferedReader bufferedReader = new BufferedReader(keyFileReader);
   FileInputStream textFileInputStream = new FileInputStream(textFile);
   FileOutputStream cipherFileOutputStream = new FileOutputStream(cipherFile);
   byte[] key = new byte[(int) keyFile.length()];
   String keyString = bufferedReader.readLine();
   key = des.hexStringToByteArray(keyString);
   byte[] message = new byte[(int) textFile.length()];
   textFileInputStream.read(message);        
   byte[] cipher = des.crypt(message, key, "encrypt");   
   cipherFileOutputStream.write(cipher);
   cipherFileOutputStream.flush();
   cipherFileOutputStream.close();
   bufferedReader.close();
   textFileInputStream.close();
   System.out.println("Encryption done! Please check DESciphertext.txt for output!");
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }
  
}

Decryption - DESdecrypt.java
 
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Arrays;


public class DESdecrypt {
 
 private String mode = null;
 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
 
 /* Initial Permutation */
 static final int[] IP = {
  58, 50, 42, 34, 26, 18, 10, 2,
  60, 52, 44, 36, 28, 20, 12, 4,
  62, 54, 46, 38, 30, 22, 14, 6,
  64, 56, 48, 40, 32, 24, 16, 8,
  57, 49, 41, 33, 25, 17,  9, 1,
  59, 51, 43, 35, 27, 19, 11, 3,
  61, 53, 45, 37, 29, 21, 13, 5,
  63, 55, 47, 39, 31, 23, 15, 7
 };
 /* Inverse Initial Permutation */
 static final int[] IIP = {
  40, 8, 48, 16, 56, 24, 64, 32,
  39, 7, 47, 15, 55, 23, 63, 31,
  38, 6, 46, 14, 54, 22, 62, 30,
  37, 5, 45, 13, 53, 21, 61, 29,
  36, 4, 44, 12, 52, 20, 60, 28,
  35, 3, 43, 11, 51, 19, 59, 27,
  34, 2, 42, 10, 50, 18, 58, 26,
  33, 1, 41,  9, 49, 17, 57, 25
 };
 /* Expansion Permutation */
 static final int[] E = {
  32,  1,  2,  3,  4,  5,
  4,  5,  6,  7,  8,  9,
  8,  9, 10, 11, 12, 13,
  12, 13, 14, 15, 16, 17,
  16, 17, 18, 19, 20, 21,
  20, 21, 22, 23, 24, 25,
  24, 25, 26, 27, 28, 29,
  28, 29, 30, 31, 32,  1
 };
 /* Permutation Function */
 static final int[] P = {
  16,  7, 20, 21,
  29, 12, 28, 17,
  1, 15, 23, 26,
  5, 18, 31, 10,
  2,  8, 24, 14,
  32, 27,  3,  9,
  19, 13, 30,  6,
  22, 11,  4, 25
 };
 /* S-Boxes*/
 static final int[] S1 = {
  14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
   0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
   4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
  15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
 };
 static final int[] S2 = {
  15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
   3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
   0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
  13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
 };
 static final int[] S3 = {
  10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
  13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
  13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
   1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
 };
 static final int[] S4 = {
   7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
  13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
  10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
   3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
 };
 static final int[] S5 = {
   2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
  14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
   4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
  11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
 };
 static final int[] S6 = {
  12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
  10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
   9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
   4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
 };
 static final int[] S7 = {
   4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
  13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
   1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
   6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
 };
 static final int[] S8 = {
  13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
   1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
   7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
   2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
 };
 /* Permuted Choice One */
 static final int[] PC1 = {
  57, 49, 41, 33, 25, 17,  9,
   1, 58, 50, 42, 34, 26, 18,
  10,  2, 59, 51, 43, 35, 27,
  19, 11,  3, 60, 52, 44, 36,
  63, 55, 47, 39, 31, 23, 15,
   7, 62, 54, 46, 38, 30, 22,
  14,  6, 61, 53, 45, 37, 29,
  21, 13,  5, 28, 20, 12,  4
 };
 /* Permuted Choice Two */
 static final int[] PC2 = {
  14, 17, 11, 24,  1,  5,
   3, 28, 15,  6, 21, 10,
  23, 19, 12,  4, 26,  8,
  16,  7, 27, 20, 13,  2,
  41, 52, 31, 37, 47, 55,
  30, 40, 51, 45, 33, 48,
  44, 49, 39, 56, 34, 53,
  46, 42, 50, 36, 29, 32
 };
 /* Schedule of Left Shifts */
 static final int[] SHIFTS = {
  1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
 };
 
 public DESdecrypt() {
  this.mode = "ECB";
 }
 
 public DESdecrypt(String mode) {
  this.mode = mode;
 }
 
 private byte[] performXOR(byte[] one, byte[] two) {
  byte[] result = new byte[one.length];
  for (int i = 0 ; i < one.length ; i++) {
   result[i] = (byte) (one[i] ^ two[i]);
  }
  return result;
 }
 
 private byte[] permute(byte[] input, int[] mapping) {
  int byteCount = 1 + (mapping.length - 1) / 8;
  byte[] output = new byte[byteCount];
  int pos;
  
  for (int i = 0 ; i < mapping.length ; i++) {
   pos = mapping[i] - 1;
   int value = getBitFromArray(input, pos);
   setBitInArray(output, i, value);
  }  
  return output;
 } 

 private int getBitFromArray(byte[] array, int pos) {
  int value;
  int bytePos = pos / 8;
  int bitPos = pos % 8;  
  value = (array[bytePos] >> (8 - (bitPos + 1))) & 0x0001;  
  /* eg: right shift selected byte 5 times to get 3rd bit 
   * (bitPos = 2) at rightmost position and 
   * then AND with 0x0001*/
  return value;
 }
 
 private void setBitInArray(byte[] input, int pos, int value) {
  int bytePos = pos / 8;
  int bitPos = pos % 8;  
  byte old = input[bytePos];
  old = (byte) (((0xFF7F >> bitPos) & old) & 0x00FF);
  byte newByte = (byte) ((value << (8 - (bitPos + 1))) | old);
     input[bytePos] = newByte;
 }
 
 private byte[] hexStringToByteArray(String string) {
  int length = string.length();
  int n = (int)Math.ceil((length + 1) / 2);
  byte[] result = new byte[n];  
  for (int i = length - 1; i >= 0 ; i -= 2) { 
   if (i == 0) {
    result[i / 2] = (byte) ((Character.digit('0', 16) << 4)
      + Character.digit(string.charAt(i), 16));
   } else {
    result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4)
     + Character.digit(string.charAt(i), 16));
   }
  }
  return result;
 }
 
 public static String bytesToHex(byte[] bytes) {
     char[] hexChars = new char[bytes.length * 2];
     for ( int j = 0; j < bytes.length; j++ ) {
         int v = bytes[j] & 0xFF;
         hexChars[j * 2] = hexArray[v >>> 4];
         hexChars[j * 2 + 1] = hexArray[v & 0x0F];
     }
     return new String(hexChars);
 }
 
 private void printBytes(byte[] input) {    
  for (int i = 0 ; i < input.length; i++) {
   System.out.print(byteToBits(input[i]) + " ");
  }
  System.out.println();
 }
 
 private String byteToBits(byte b) {
  StringBuffer buffer = new StringBuffer();
  for (int i = 0 ; i < 8 ; i++)
   buffer.append((int)(b >> (8-(i+1)) & 0x0001));
  return buffer.toString();
 }

 private byte[] getBits(byte[] input, int startPos, int length) {
  int noOfBytes = (length-1)/8 + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < length ; i++) {
   int value = getBitFromArray(input, startPos + i);
   setBitInArray(output, i, value);
  }
  return output;
 } 
 
 private byte[] rotateLeft(byte[] input, int step, int length) {  
  int noOfBytes = (length - 1) / 8 + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < length ; i++) {
   int value = getBitFromArray(input, (i + step) % length);
   setBitInArray(output, i, value);
  }
  return output;
 }
 
 private byte[] concatBits(byte[] one, int oneLength, 
   byte[] two, int twoLength) {
  int noOfBytes = (oneLength + twoLength - 1) / 8 + 1;
  byte[] output = new byte[noOfBytes];
  int i = 0, j = 0;
  for (; i < oneLength ; i++) {
   int value = getBitFromArray(one, i);
   setBitInArray(output, j, value);
   j++;
  }  
  for (i = 0 ; i < twoLength ; i++) {
   int value = getBitFromArray(two, i);
   setBitInArray(output, j, value);
   j++;
  }
  return output;
 }
 
 private byte[][] getSubKeys(byte[] masterKey) {
  int noOfSubKeys = SHIFTS.length;
  int keySize = PC1.length;
  byte[] key = permute(masterKey, PC1);
  byte[][] subKeys = new byte[noOfSubKeys][keySize];
  byte[] leftHalf = getBits(key, 0, keySize/2);
  byte[] rightHalf = getBits(key, keySize/2, keySize/2);
  for (int i = 0 ; i < noOfSubKeys ; i++) {
   leftHalf = rotateLeft(leftHalf, SHIFTS[i], keySize/2);
   rightHalf = rotateLeft(rightHalf, SHIFTS[i], keySize/2);
   byte[] subKey = concatBits(leftHalf, keySize/2, rightHalf, keySize/2);
   subKeys[i] = permute(subKey, PC2); 
  }
  return subKeys;
 }
 
 public byte[] crypt(byte[] message, byte[] key, String operation) {
  if (message.length < 8) {
   System.out.println("Message should be atleast 64 bits");
   System.exit(1);
  }
  if (key.length != 8) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  int length = message.length;
  int n = (length + 7)/8 * 8;
  byte[] cipher = new byte[n];
  if (length == 8) {
   if (mode.equals("ECB")) {
    return cryptText(message, key, operation);
   } else if (mode.equals("CBC")) {
    byte[] iv = getInitializationVector();
    message = XORBytes(message, iv);
    return cryptText(message, key, operation);
   } else if (mode.equals("OFB")) {    
    byte[] nounce = getNounce();
    byte[] temp = cryptText(nounce, key, "encrypt");
    byte[] result = XORBytes(temp, message);
    return result;
   } else if (mode.equals("CFB")) {
    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
  }
  int i = 0;
  int k = 0;
  byte[] feedback = new byte[8];  
  if (mode.equals("CBC")) {
   feedback = getInitializationVector();
  } else if (mode.equals("OFB")) {
   feedback = getNounce();   
  } else if (mode.equals("CFB")) {
   feedback = getInitializationVectorCFB();
  }
  
  while (i < length) {
   byte[] block = new byte[8];
   byte[] result = new byte[8];
   int j = 0;
   for (; j < 8 && i < length; j++, i++) {
    block[j] = message[i];
   }
   while (j < 8) {
    /* pad with white spaces */
    block[j++] = 0x20;
   }
      
   //System.out.println("BLOCK: ");
   //printBytes(block);  
   if (mode.equals("ECB")) {
    result = cryptText(block, key, operation);
   } else if (mode.equals("CBC")) {
    if (operation.equals("encrypt")) {
     block = XORBytes(block, feedback);
     result = cryptText(block, key, operation);
     feedback = Arrays.copyOfRange(result, 0, 8);
    } else if (operation.equals("decrypt")) {
     result = cryptText(block, key, operation);
     result = XORBytes(result, feedback);
     feedback = Arrays.copyOfRange(block, 0, 8);
    }    
   } else if (mode.equals("OFB")) {
    result = cryptText(feedback, key, "encrypt");
    feedback = Arrays.copyOfRange(result, 0, 8);
    result = XORBytes(result, block);    
   } else if (mode.equals("CFB")) {
    if (operation.equals("encrypt")) {
     result = cryptText(feedback, key, operation);
     byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
     byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
     byte[] temp1 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp1);     
     resultPart = Arrays.copyOfRange(result, 4, 8);
     blockPart = Arrays.copyOfRange(block, 4, 8);
     result = cryptText(feedback, key, operation);
     byte[] temp2 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp2);
     result = mergeBytes(temp1, temp2);
    } else if (operation.equals("decrypt")) {
     result = cryptText(feedback, key, "encrypt");
     byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
     byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
     byte[] temp1 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);     
     resultPart = Arrays.copyOfRange(result, 4, 8);
     blockPart = Arrays.copyOfRange(block, 4, 8);
     result = cryptText(feedback, key, "encrypt");
     byte[] temp2 = XORBytes(resultPart, blockPart);
     feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
     result = mergeBytes(temp1, temp2);
    }    
   } else {
    System.out.println("Unsupported mode of operation!");
    return null;
   }   
   //System.out.println("RESULT: ");
   //printBytes(result);
   for (j = 0 ; j < 8 && k < cipher.length; j++, k++) {
    cipher[k] = result[j];
   }
  }
  return cipher;  
 }
 
 private byte[] getInitializationVector() {
  return hexStringToByteArray("DCBE6AE7EA5D5C61");   
 }
 
 private byte[] getInitializationVectorCFB() {
  return hexStringToByteArray("A5D5C61EFADB4351");   
 }
 
 private byte[] getNounce() {
//  char[] hexArray = "0123456789ABCDEF".toCharArray();
//  String nounceStr = "";
//  for (int i = 0 ; i < 16 ; i++) {
//   double random = Math.random();
//   int index = (int) (random * 16);
//   nounceStr += hexArray[index];   
//  }
//  return hexStringToByteArray(nounceStr);
  return hexStringToByteArray("DCBE6AE7EA5D5C61");
 } 

 private byte[] mergeBytes(byte[] in1, byte[] in2) {
  byte[] out = new byte[in1.length + in2.length];
  int i = 0;
  for (int j = 0 ; j < in1.length ; j++) {
   out[i++] = in1[j];
  }
  for (int j = 0 ; j < in2.length ; j++) {
   out[i++] = in2[j];
  }
  return out;
 }
 public byte[] cryptText(byte[] message, byte[] key, String operation) {
  if (message.length != 8) {
   System.out.println("Message should be 64 bits");
   System.exit(1);
  }
  if (key.length != 8) {
   System.out.println("Key should be 64 bits");
   System.exit(1);
  }
  byte[] result = null;
  int blockSize = IP.length;
  byte[][] subKeys = getSubKeys(key);
  int noOfRounds = subKeys.length;
  /**
   * Initial Permutation
   */
  message = permute(message, IP);
  /**
   * Split message into two halves
   */
  byte[] leftHalf = getBits(message, 0, blockSize/2);
  byte[] rightHalf = getBits(message, blockSize/2, blockSize/2);
  for (int i = 0 ; i < noOfRounds ; i++) {
   byte[] temp = rightHalf;
   /**
    * Expansion
    */
   rightHalf = permute(rightHalf, E);
   /**
    * XOR rightHalf with roundKey
    */
   byte[] roundKey = null;
   if (operation.equalsIgnoreCase("encrypt")) {
    roundKey = subKeys[i];
   } else if (operation.equalsIgnoreCase("decrypt")) {
    roundKey = subKeys[noOfRounds - i - 1];
   } else {
    System.out.println("Unsupported operation");
    System.exit(0);
   }
   rightHalf = performXOR(rightHalf, roundKey);
   /**
    * S-Box
    */
   rightHalf = sBox(rightHalf);
   /**
    * Permutation
    */
   rightHalf = permute(rightHalf, P);
   /**
    * XOR rightHalf with leftHalf
    */
   rightHalf = performXOR(rightHalf, leftHalf);
   /**
    * L(i) = R(i-1)
    */
   leftHalf = temp;
  }
  /**
   * 32 bit swap
   */
  byte[] concatHalves = concatBits(rightHalf, blockSize/2, leftHalf, blockSize/2);
  /**
   * Inverse Initial Permutation
   */
  result = permute(concatHalves, IIP);
  return result;
 }
 
 public static byte[] XORBytes(byte[] in1, byte[] in2) {  
  byte[] out = new byte[in1.length];
  for (int i = 0 ; i < in1.length ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }
  return out;
 }
 
 private byte[] sBox(byte[] input) {  
  /**
   * Split input to 6-bit blocks
   */
  input = split(input,6);
  byte[] output = new byte[input.length/2];
  int leftHalf = 0;  
  for (int i = 0; i < input.length ; i++) {
   byte block = input[i];   
   /**
    * row - first and last bits
    * column - 4 bits in the middle
    */
   int row = 2 * (block >> 7 & 0x0001) + (block >> 2 & 0x0001);
   int col = block >> 3 & 0x000F;
   int[] selectedSBox = getSBox(i);
   int rightHalf = selectedSBox[16 * row + col];
   if (i % 2 == 0) {
    leftHalf = rightHalf;
   } else {
    output[i/2] = (byte) (16 * leftHalf + rightHalf);
    leftHalf = 0;
   }
  }
  return output;
 }

 private int[] getSBox(int i) {
  switch (i) {
   case 0: return S1;
   case 1: return S2;
   case 2: return S3;
   case 3: return S4;
   case 4: return S5;
   case 5: return S6;
   case 6: return S7;
   case 7: return S8; 
   default: return null;   
  }
 }

 private byte[] split(byte[] input, int length) {
  int noOfBytes = (8 * input.length - 1) / length + 1;
  byte[] output = new byte[noOfBytes];
  for (int i = 0 ; i < noOfBytes ; i++) {
   for (int j = 0; j < length ; j++) {
    int value = getBitFromArray(input, length * i + j);    
    setBitInArray(output, 8 * i + j, value);
   }
  }
  return output;
 }

 public static void main(String[] args) {
  try {
   if (args.length != 1) {
    System.out.println("Usage: java < classname > < mode >"
      + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
    return;
   }
   /* ECB, CBC, OFB, or CFB */
   String mode = args[0];
   mode = mode.toUpperCase();
   DESdecrypt des = new DESdecrypt(mode); 
   File keyFile = new File("DESkey.txt");
   File textFile = new File("DESplaintext.txt");
   File cipherFile = new File("DESciphertext.txt");   
   FileReader keyFileReader = new FileReader(keyFile);
   BufferedReader bufferedReader = new BufferedReader(keyFileReader);
   FileInputStream cipherFileInputStream = new FileInputStream(cipherFile);
   FileOutputStream textFileOutputStream = new FileOutputStream(textFile);
   byte[] key = new byte[(int) keyFile.length()];
   String keyString = bufferedReader.readLine();
   key = des.hexStringToByteArray(keyString);
   byte[] cipher = new byte[(int) cipherFile.length()];
   cipherFileInputStream.read(cipher);        
   byte[] message = des.crypt(cipher, key, "decrypt");   
   textFileOutputStream.write(message);
   textFileOutputStream.flush();
   textFileOutputStream.close();
   bufferedReader.close();
   cipherFileInputStream.close();
   System.out.println("Decryption done! Please check DESplaintext.txt for output!");
  } catch(Exception exp) {
   exp.printStackTrace();
  }
 }
  
}

Output
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESkeygen
Key generated and saved in DESkey.txt
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt
Usage: java <classname> <mode>
<mode> := (ECB|CBC|OFB|CFB)
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt ecb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt ecb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt cbc
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cbc
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt ofb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt ofb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt cfb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cfb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cfb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ 

About Input/Output Files
DESkeygen.java - (output) DESkey.txt 

DESencrypt.java - (input) DESkey.txt & DESplaintext.txt (output) DESciphertext.txt 
DESdecrypt.java - (input) DESkey.txt & DESciphertext.txt (output) DESplaintext.txt

AES Implementation in Java

AES.java

 
import java.util.Arrays;

public class AES {
 
 private static final int BITS = 16;
 private static final int ROUNDS = 10;
 private static final int NO_OF_WORDS_IN_KEY = 44;
 private static final int KEY_LENGTH = 16;
 private static final int BLOCK_LENGTH = 16;
 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
 int[] RC = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36};
 Word[] Rcon = new Word[ROUNDS]; 
 private byte[] word = null;
 
 static final int[] sBox = {
  0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
 };
  
 static final int[] invSBox = {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 
  0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 
  0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 
  0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 
  0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 
  0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 
  0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 
  0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 
  0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 
  0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 
  0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 
  0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 
  0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
 };
  
 
 public AES() {
  for (int i = 0 ; i < ROUNDS ; i++) {
   Rcon[i] = new Word();
   byte[] temp = new byte[4];
   temp[0] = (byte) (RC[i] & 0xff);
   temp[1] = 0;
   temp[2] = 0;
   temp[3] = 0;
   Rcon[i].setWord(temp);   
  }
  word = new byte[NO_OF_WORDS_IN_KEY];
 }
 
 /* Ref: http://www.samiam.org/galois.html */
 /* Galois Addition*/
 byte gadd(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Subtraction*/
 byte gsub(byte a, byte b) {
  return (byte) ((a ^ b) & 0xff);
 }
 /* Galois Multiplication*/
 byte gmul(byte a, byte b) {
  byte p = 0;
  int counter;
  byte high_bit_set;
  byte byte0x80 = hexStringToByteArray("80")[0];
  for (counter = 0 ; counter < 8 ; counter++) {
   if((b & 0x01) == 1) {
    //System.out.println("lower bit of b is set");
    p = (byte)((p ^ a) & 0xff);
   }   
   high_bit_set = (byte) (a & 0x80);
   //printByte("high_bit_set", high_bit_set);
   a <<= 1;
   if (high_bit_set == byte0x80) {
    //System.out.println("higher bit of a is set");
    a = (byte)((a ^ 0x1b) & 0xff);
   }
   b = (byte)((b >> 1) & 0x7f);
   
   //printByte("a", a);
   //printByte("b", b);
   //printByte("p", p);
  }
  return p;
 }
 
 byte gmul(byte a, int b) {
  byte t = (byte)(b & 0xff);
  return gmul(a, t);
 }
 
 /* Key Expansion */
 private byte[] expandKey(byte[] key) throws Exception {
  //System.out.println(key.length);
  //System.out.println(bytesToHex(key));
  if(key.length != KEY_LENGTH) {
   throw new Exception("Key should be of length, 128 bits");
  }
  Word[] w = new Word[NO_OF_WORDS_IN_KEY]; 
  Word temp;
  for (int i = 0; i < 4; i++) {
   w[i] = new Word(key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]); 
   //System.out.println("w" + i + " = " + w[i]);
  }
  
  for (int i = 4; i < 44; i++) {
   temp = w[i-1];
   Word temp1 = new Word();
   temp1.setWord(temp.getWord());
   //System.out.println("w" + (i-1) + " = " + temp);
   if (i % 4 == 0) {
    temp1.rotWord();
    //System.out.println("Rot=" + temp1);
    temp1.subWord();
    //System.out.println("Sub=" + temp1);
    temp1 = Word.XORWords(temp1, Rcon[(i/4) - 1]);
    //System.out.println("Rcon" + temp1);
   }
   w[i] = Word.XORWords(w[i-4], temp1);
   //System.out.println("w" + i + " = " + w[i]);   
  }
  return Word.wordsToBytes(w);
 }
 
 /* Substitute Bytes */
 private byte[] subBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) sBox[row * BITS + col];
  }
  return out;
 }
 
 /* Inverse Substitute Bytes */
 private byte[] inverseSubBytes(byte[] in) {
  byte[] out = new byte[BITS];
  for (int i = 0 ; i < BITS ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) invSBox[row * BITS + col];
  }
  return out;
 }
 
 /* Shift Rows */
 private byte[] shiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  //System.out.println("temp: " + bytesToHex(temp));
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = leftShift(a, i);
   in[4*i] = b[0];
   in[4*i+1] = b[1];
   in[4*i+2] = b[2];
   in[4*i+3] = b[3];
  }   
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] leftShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[1];
   out[1] = in[2];
   out[2] = in[3];
   out[3] = in[0];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Inverse Shift Rows */
 private byte[] inverseShiftRows(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   byte[] a = Arrays.copyOfRange(temp, (4 * i), (4 * i + 4));
   byte[] b = rightShift(a, i);
   in[4 * i] = b[0];
   in[4 * i + 1] = b[1];
   in[4 * i + 2] = b[2];
   in[4 * i + 3] = b[3];
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    out[4*j+i] = in[4*i+j];
   }
  }
  return out;
 }
 
 private byte[] rightShift(byte[] in, int times) {
  byte[] out = new byte[4];
  out = Arrays.copyOfRange(in, 0, 4);
  for (int i = 0 ; i < times ; i++) {
   out[0] = in[3];
   out[1] = in[0];
   out[2] = in[1];
   out[3] = in[2];
   in = Arrays.copyOfRange(out, 0, 4);
  }
  return out;
 }
 
 /* Mix Columns */
 private byte[] mixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 2)  ^ gmul(in[4*1+j], 3)  ^ in[4*2+j]    ^ in[4*3+j])    & 0xff);
   out[4*1+j] = (byte) ((in[4*0+j]    ^ gmul(in[4*1+j], 2)  ^ gmul(in[4*2+j], 3)  ^ in[4*3+j])    & 0xff);
   out[4*2+j] = (byte) ((in[4*0+j]    ^ in[4*1+j]    ^ gmul(in[4*2+j], 2)  ^ gmul(in[4*3+j], 3))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 3)  ^ in[4*1+j]    ^ in[4*2+j]    ^ gmul(in[4*3+j], 2))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 /* Inverse Mix Columns */
 private byte[] inverseMixColumns(byte[] in) {
  byte[] out = new byte[BITS];
  byte[] temp = new byte[BITS];  
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = in[4*i+j];
   }
  }
  in = temp;
  for (int j = 0 ; j < BITS/4 ; j++) {
   out[4*0+j] = (byte) ((gmul(in[4*0+j], 14)  ^ gmul(in[4*1+j], 11)  ^ gmul(in[4*2+j], 13)  ^ gmul(in[4*3+j], 9))  & 0xff);
   out[4*1+j] = (byte) ((gmul(in[4*0+j], 9)  ^ gmul(in[4*1+j], 14)  ^ gmul(in[4*2+j], 11)  ^ gmul(in[4*3+j], 13))  & 0xff);
   out[4*2+j] = (byte) ((gmul(in[4*0+j], 13)  ^ gmul(in[4*1+j], 9) ^ gmul(in[4*2+j], 14)  ^ gmul(in[4*3+j], 11))  & 0xff);
   out[4*3+j] = (byte) ((gmul(in[4*0+j], 11)  ^ gmul(in[4*1+j], 13) ^ gmul(in[4*2+j], 9) ^ gmul(in[4*3+j], 14))  & 0xff);
  }
  for (int i = 0 ; i < BITS/4 ; i++) {
   for (int j = 0 ; j < BITS/4 ; j++) {
    temp[4*j+i] = out[4*i+j];
   }
  }
  out = temp;
  return out;
 }
 
 private byte[] hexStringToByteArray(String string) {
  int length = string.length();
  int n = (int)Math.ceil((length + 1) / 2);
  byte[] result = new byte[n];  
  for (int i = length - 1; i >= 0 ; i -= 2) { 
   if (i == 0) {
    result[i / 2] = (byte) ((Character.digit('0', 16) << 4)
      + Character.digit(string.charAt(i), 16));
   } else {
    result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4)
     + Character.digit(string.charAt(i), 16));
   }
  }
  return result;
 }
 
 /* http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java */
 public static String bytesToHex(byte[] bytes) {
     char[] hexChars = new char[bytes.length * 2];
     for ( int j = 0; j < bytes.length; j++ ) {
         int v = bytes[j] & 0xFF;
         hexChars[j * 2] = hexArray[v >>> 4];
         hexChars[j * 2 + 1] = hexArray[v & 0x0F];
     }
     return new String(hexChars);
 }
 
 private void printBytes(byte[] input) {    
  for (int i = 0 ; i < input.length; i++) {
   System.out.print(byteToBits(input[i]) + " ");
  }
  System.out.println();
 }
 
 private void printByte(String msg, byte input) {
  byte[] temp = new byte[1];
  temp[0] = input;
  System.out.println(msg + ": " + bytesToHex(temp));  
 }
 
 private String byteToBits(byte b) {
  StringBuffer buffer = new StringBuffer();
  for (int i = 0 ; i < 8 ; i++)
   buffer.append((int)(b >> (8-(i+1)) & 0x0001));
  return buffer.toString();
 }
 
 private byte[] getRoundKey(int round) {
  byte[] out = new byte[KEY_LENGTH];
  out = Arrays.copyOfRange(word, 16*round, 16*round+16);  
  return out;
 }
 
 public static byte[] XORBytes(byte[] in1, byte[] in2) {  
  byte[] out = new byte[BLOCK_LENGTH];
  for (int i = 0 ; i < BLOCK_LENGTH ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }   
  return out;
 }
 
 public byte[] encrypt(byte[] plainText, byte[] key) throws Exception {
  byte[] cipher = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(0);
  /* Round 0 */
  cipher = XORBytes(plainText, roundKey);
  //System.out.println("Round 0\n" + bytesToHex(cipher));
  /* Rounds 1 to 9*/
  for (int i = 1 ; i < 10 ; i++) {
   //System.out.println("Round " + i);
   cipher = subBytes(cipher);
   //System.out.println("SubBytes: " + bytesToHex(cipher));
   cipher = shiftRows(cipher);
   //System.out.println("ShiftRows: " + bytesToHex(cipher));
   cipher = mixColumns(cipher);
   //System.out.println("MixColumns: " + bytesToHex(cipher));
   roundKey = getRoundKey(i);
   //System.out.println("RoundKey: " + bytesToHex(roundKey));
   cipher = XORBytes(cipher, roundKey);   
   //System.out.println("CIPHER: " + bytesToHex(cipher));
  }
  /* Round 10*/
  //System.out.println("Round 10");
  cipher = subBytes(cipher);
  //System.out.println("SubBytes: " + bytesToHex(cipher));
  cipher = shiftRows(cipher);
  //System.out.println("ShiftRows: " + bytesToHex(cipher));
  roundKey = getRoundKey(10);
  //System.out.println("RoundKey: " + bytesToHex(roundKey));
  cipher = XORBytes(cipher, roundKey);
  //System.out.println("CIPHER: " + bytesToHex(cipher));
  return cipher;
 }
 
 public byte[] decrypt(byte[] cipher, byte[] key) throws Exception {
  byte[] plainText = new byte[BLOCK_LENGTH];  
  this.word = expandKey(key);
  byte[] roundKey = getRoundKey(10);
  /* Round 0 */
  plainText = XORBytes(cipher, roundKey);
  /* Rounds 1 to 9*/
  for (int i = 9 ; i > 0 ; i--) {
   plainText = inverseShiftRows(plainText);
   plainText = inverseSubBytes(plainText);
   roundKey = getRoundKey(i);
   plainText = XORBytes(plainText, roundKey);
   plainText = inverseMixColumns(plainText);
  }
  /* Round 10*/
  plainText = inverseShiftRows(plainText);
  plainText = inverseSubBytes(plainText);
  roundKey = getRoundKey(0);
  plainText = XORBytes(plainText, roundKey);
  return plainText;
 }
 
 public static void main(String[] args) throws Exception {
  AES aes = new AES();
  byte[] plainText = aes.hexStringToByteArray("0123456789abcdeffedcba9876543210");
  System.out.println("PLAIN TEXT: " + bytesToHex(plainText));
  byte[] key = aes.hexStringToByteArray("0f1571c947d9e8590cb7add6af7f6798");
  System.out.println("KEY: " + bytesToHex(key));
  byte[] cipher = aes.encrypt(plainText, key);
  System.out.println("CIPHER TEXT: " + bytesToHex(cipher)); 
  plainText = aes.decrypt(cipher, key);
  System.out.println("DECRYPTED CIPHER TEXT: " + bytesToHex(plainText));
    
 }
}
Word.java

 

public class Word {
 
 private byte[] word = null;
 
 public Word() {
  word = new byte[4];
 }
 
 public Word(byte k0, byte k1, byte k2, byte k3) {
  this();
  word[0] = k0;
  word[1] = k1;
  word[2] = k2;
  word[3] = k3;
 }
 
 public byte[] getWord() {
  return word;
 }
 
 public void setWord(byte[] word) {
  this.word = word;
 }
 
 public static byte[] wordToBytes(Word word) {
  return word.getWord();
 }
 
 public static byte[] wordsToBytes(Word[] words) {
  byte[] out = new byte[4 * words.length];
  for (int i = 0 ; i < words.length ; i++) {
   byte[] temp = words[i].getWord();
   out[4*i] = temp[0];
   out[4*i+1] = temp[1];
   out[4*i+2] = temp[2];
   out[4*i+3] = temp[3];   
  }
  return out;
 }
 
 public void rotWord() {
  byte[] temp = this.getWord();
  byte[] newWord = new byte[4];
  newWord[0] = temp[1];
  newWord[1] = temp[2];
  newWord[2] = temp[3];
  newWord[3] = temp[0]; 
  this.setWord(newWord);
 }
 
 public void subWord() {
  byte[] in = this.getWord();
  byte[] out = new byte[4];  
  for (int i = 0 ; i < 4 ; i++) {
   byte a = in[i];
   int row = (a >> 4) & 0x000F;
   int col = a & 0x000F;   
   out[i] = (byte) AES.sBox[row * 16 + col];
  }
  for (int i = 0 ; i < 4 ; i++) {
   this.word[i] = out[i];
  }  
 } 
 
 public static Word XORWords(Word word1, Word word2) {
  Word outWord = new Word();
  byte[] in1 = word1.getWord();
  byte[] in2 = word2.getWord();
  byte[] out = new byte[4];
  for (int i = 0 ; i < 4 ; i++) {
   out[i] = (byte)((in1[i] ^ in2[i]) & 0xff);
  }
  outWord.setWord(out);  
  return outWord;
 }
 
 public String toString() {
  return AES.bytesToHex(this.getWord());
 }
}

Output

PLAIN TEXT: 0123456789ABCDEFFEDCBA9876543210
KEY: 0F1571C947D9E8590CB7ADD6AF7F6798
CIPHER TEXT: FF0B844A0853BF7C6934AB4364148FB9
DECRYPTED CIPHER TEXT: 0123456789ABCDEFFEDCBA9876543210

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