AES

AES.java

import java.math.BigInteger;
import java.security.NoSuchAlgorithmException;

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


public class AES {

	/**************************************************
	 * HELPER/UTILITY AES FUNCTIONS
	 */

	public String[] splitStringToArray(String input)
	{
		String[] array = new String[ input.length()/2];

		for(int i = 0; i< array.length; i++ )
		{
			array[i] = input.substring(2*i, 2*i + 2);
		}

		return array;
	}

	public String mergeStringFromArray(String[] input)
	{
		String str = "";
		for(int i=0; i< input.length; i++)
		{
			str += input[i];
		}
		return str;
	}

	private void PrintStateArray(int i )
	{
		System.out.print(" Round "+i+" Encryption: ");
		for(int r = 0; r < 4; r++)
		{
			for(int c = 0; c < 4; c++)
			{
				System.out.print(state[ r  ][ c ]);
			}
		}
		System.out.print("\n");
	}
	//Number to String Byte
	private String hString(int num )
	{
		String fmt = String.format("%02X",num);

		if( fmt.length() > 2 )
		{
			fmt = fmt.substring(1);
		}

		return fmt;
	}

	/**************************************************
	 * CORE AES FUNCTIONS
	 */

	int Nk = 4;
	int Nr = 10;
	int Nb = 4;
	String state[][];
	String[] keyExpansion;

	public AES()
	{
		state = new String[4][4];
	}

	private void AddRoundKey( int round )
	{

		for(int r = 0; r < 4; r++)
		{
			for(int c = 0; c < 4; c++)
			{
				int word = Integer.parseInt(keyExpansion[round*4+c].substring(2*r, 2*r +2),16);
				int st = Integer.parseInt(state[r][c],16);
				int res = st ^ word;
				state[r][c] = String.format("%02X",  res);
			}
		}
	}

	private void SubBytes()
	{
		for(int r = 0; r < 4 ; r++)
		{
			for(int c = 0; c < 4 ; c++)
			{
				state[r][c] = sBox[ Integer.parseInt( state[r][c], 16 ) ];
			}
		}
	}

	private void ShiftRows()
	{
		for(int r = 1; r < 4 ; r++)
		{
			String[] temp = new String[4];
			for(int c = 0; c < 4 ; c++)
			{
				temp[c] = state[r][(c+r)%4];
			}
			System.arraycopy(temp, 0, state[r], 0, 4);
		}
	}

	private void MixColumns()
	{
        for(int c = 0; c < 4; c++) {
        	
            int[] a = new int[4];
            int[] b = new int[4];
            int h;
            
            
        	for(int r = 0; r < 4; r++)
        	{
        		 a[r] = Integer.parseInt(state[r][c], 16);
        		 h = Integer.parseInt(state[r][c],16) & 0x80; /* hi bit */
        		 
        		 b[r] = Integer.parseInt(state[r][c],16) << 1;
        		 
        		 if( h == 0x80) 
                     b[r] ^= 0x1B; /* Rijndael's Galois field */
        	}
        	
            state[0][c] = hString(b[0] ^ a[3] ^ a[2] ^ b[1] ^ a[1]);
            state[1][c] = hString(b[1] ^ a[0] ^ a[3] ^ b[2] ^ a[2]);
            state[2][c] = hString(b[2] ^ a[1] ^ a[0] ^ b[3] ^ a[3]);
            state[3][c] = hString(b[3] ^ a[2] ^ a[1] ^ b[0] ^ a[0]);
        }
	}

	private String SubWord(String input)
	{
		String[] arrayinput = splitStringToArray(input);

		for(int i = 0; i < 4; i++ )
		{
			arrayinput[i] = sBox[Integer.parseInt(arrayinput[i], 16)];
		}
		return mergeStringFromArray(arrayinput);
	}

	private String RotWord(String input)
	{
		String[] arrayinput = splitStringToArray(input);

		String temp = arrayinput[0];

		for(int i = 0; i < 3; i++)
		{
			arrayinput[i] = arrayinput[i+1];
		}
		arrayinput[3] = temp;

		return mergeStringFromArray(arrayinput);
	}

	private void KeyExpansion(String Key)
	{
		keyExpansion = new String[4 * Nb *(Nr + 1)]; //176 bytes

		for(int i = 0; i < Nk ; i++ )
		{
			keyExpansion[i] = Key.substring(8*i, 8*i + 2) + Key.substring(8*i + 2, (8*i+2) + 2) + 
							 Key.substring(8*i +4, (8*i+4) + 2) + Key.substring(8*i+6, (8*i+6) + 2);
			System.out.println("i="+i+" | expandedKey[i] = Key[4i]  + Key [4i+1]  +  Key[4i+2]  + Key[4i+3] = "+keyExpansion[i]);
		}

		for(int i = Nk; i < Nb *(Nr + 1); i++)
		{
			String temp = keyExpansion[i - 1];

			if( i % Nk == 0)
			{
				BigInteger RconValue = new BigInteger(Rcon[i/Nk],16);
				//System.out.println("Rcon["+i/Nk+"] = "+ String.format("%0" + (4 << 1) + "X", RconValue));

				String rotword = RotWord(temp);
				String subword = SubWord(rotword);
				temp =  String.format("%0" + (4 << 1) + "X", new BigInteger( subword ,16).xor( RconValue ) );

				System.out.print("i="+i+" | expandedKey[i] = SubWord(RotWord(w[i-1])) ^ Rcon[i/Nk] ");
			}
			else if ( Nk > 6 && i % Nk == 4)
			{
				temp = SubWord(temp);
				System.out.print("i="+i+" | expandedKey[i] = SubWord(w[i-Nk]) ");
			}
			else
			{
				System.out.print("i="+i+" | expandedKey[i] = w[i-1] ");
			}
			keyExpansion[i] =  String.format("%0" + (4 << 1) + "X", new BigInteger(keyExpansion[i-Nk], 16).xor( new BigInteger(temp,16)) );
			System.out.print("^ w[i-Nk] = "+keyExpansion[i] +"\n");
		}

	}

	public void encrypt( String PlainText, String Key)
	{

		for(int i = 0; i < 16; i++)
		{
			state[i % 4 ][ i / 4] = PlainText.substring(2 * i, 2*i + 2);
		}

		//Do Key Shedule
		KeyExpansion(Key);
		int i = 0;

		System.out.println("***************************************");
		System.out.println("Starting Encyrption: ");
		System.out.println("***************************************");

		AddRoundKey( 0 );
		PrintStateArray( i );

		for(i = 1; i < 16; i++)
		{
			SubBytes();
			ShiftRows();
			MixColumns();
			AddRoundKey( 1 );
			PrintStateArray( 1 );
		}
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {

		//String PT = "3243f6a8885a308d313198a2e0370734";
		//String Key = "2B7E151628AED2A6ABF7158809CF4F3C";

		String PT = "00112233445566778899aabbccddeeff";
		String Key = "000102030405060708090a0b0c0d0e0f";
		AES Impl = new AES();
		Impl.encrypt(PT, Key);
	}

	private String[] Rcon ={"8D000000", "01000000", "02000000", "04000000" ,"08000000" , "10000000", "20000000", "40000000" ,"80000000" , "1B000000", "36000000"};
	private String[] sBox = 
		{
		   "63", "7C", "77", "7B", "F2", "6B", "6F", "C5", "30", "01", "67", "2B", "FE", "D7", "AB", "76",
		   "CA", "82", "C9", "7D", "FA", "59", "47", "F0", "AD", "D4", "A2", "AF", "9C", "A4", "72", "C0",
		   "B7", "FD", "93", "26", "36", "3F", "F7", "CC", "34", "A5", "E5", "F1", "71", "D8", "31", "15",
		   "04", "C7", "23", "C3", "18", "96", "05", "9A", "07", "12", "80", "E2", "EB", "27", "B2", "75",
		   "09", "83", "2C", "1A", "1B", "6E", "5A", "A0", "52", "3B", "D6", "B3", "29", "E3", "2F", "84",
		   "53", "D1", "00", "ED", "20", "FC", "B1", "5B", "6A", "CB", "BE", "39", "4A", "4C", "58", "CF",
		   "D0", "EF", "AA", "FB", "43", "4D", "33", "85", "45", "F9", "02", "7F", "50", "3C", "9F", "A8",
		   "51", "A3", "40", "8F", "92", "9D", "38", "F5", "BC", "B6", "DA", "21", "10", "FF", "F3", "D2",
		   "CD", "0C", "13", "EC", "5F", "97", "44", "17", "C4", "A7", "7E", "3D", "64", "5D", "19", "73",
		   "60", "81", "4F", "DC", "22", "2A", "90", "88", "46", "EE", "B8", "14", "DE", "5E", "0B", "DB",
		   "E0", "32", "3A", "0A", "49", "06", "24", "5C", "C2", "D3", "AC", "62", "91", "95", "E4", "79",
		   "E7", "C8", "37", "6D", "8D", "D5", "4E", "A9", "6C", "56", "F4", "EA", "65", "7A", "AE", "08",
		   "BA", "78", "25", "2E", "1C", "A6", "B4", "C6", "E8", "DD", "74", "1F", "4B", "BD", "8B", "8A",
		   "70", "3E", "B5", "66", "48", "03", "F6", "0E", "61", "35", "57", "B9", "86", "C1", "1D", "9E",
		   "E1", "F8", "98", "11", "69", "D9", "8E", "94", "9B", "1E", "87", "E9", "CE", "55", "28", "DF",
		   "8C", "A1", "89", "0D", "BF", "E6", "42", "68", "41", "99", "2D", "0F", "B0", "54", "BB", "16"
		};

}