package org.spongycastle.crypto.engines;

import java.util.Hashtable;

import org.spongycastle.crypto.BlockCipher;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.DataLengthException;
import org.spongycastle.crypto.OutputLengthException;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.crypto.params.ParametersWithSBox;
import org.spongycastle.util.Arrays;
import org.spongycastle.util.Strings;

/**
 * implementation of GOST 28147-89
 */
public class GOST28147Engine
    implements BlockCipher
{
    protected static final int  BLOCK_SIZE = 8;
    private int[]               workingKey = null;
    private boolean forEncryption;

    private byte[] S = Sbox_Default;

    // these are the S-boxes given in Applied Cryptography 2nd Ed., p. 333
    // This is default S-box!
    private static byte Sbox_Default[] = {
        0x4,0xA,0x9,0x2,0xD,0x8,0x0,0xE,0x6,0xB,0x1,0xC,0x7,0xF,0x5,0x3,
        0xE,0xB,0x4,0xC,0x6,0xD,0xF,0xA,0x2,0x3,0x8,0x1,0x0,0x7,0x5,0x9,
        0x5,0x8,0x1,0xD,0xA,0x3,0x4,0x2,0xE,0xF,0xC,0x7,0x6,0x0,0x9,0xB,
        0x7,0xD,0xA,0x1,0x0,0x8,0x9,0xF,0xE,0x4,0x6,0xC,0xB,0x2,0x5,0x3,
        0x6,0xC,0x7,0x1,0x5,0xF,0xD,0x8,0x4,0xA,0x9,0xE,0x0,0x3,0xB,0x2,
        0x4,0xB,0xA,0x0,0x7,0x2,0x1,0xD,0x3,0x6,0x8,0x5,0x9,0xC,0xF,0xE,
        0xD,0xB,0x4,0x1,0x3,0xF,0x5,0x9,0x0,0xA,0xE,0x7,0x6,0x8,0x2,0xC,
        0x1,0xF,0xD,0x0,0x5,0x7,0xA,0x4,0x9,0x2,0x3,0xE,0x6,0xB,0x8,0xC
    };
    
    /*
     * class content S-box parameters for encrypting
     * getting from, see: http://tools.ietf.org/id/draft-popov-cryptopro-cpalgs-01.txt
     *                    http://tools.ietf.org/id/draft-popov-cryptopro-cpalgs-02.txt
     */
    private static byte[] ESbox_Test = {
         0x4,0x2,0xF,0x5,0x9,0x1,0x0,0x8,0xE,0x3,0xB,0xC,0xD,0x7,0xA,0x6,
         0xC,0x9,0xF,0xE,0x8,0x1,0x3,0xA,0x2,0x7,0x4,0xD,0x6,0x0,0xB,0x5,
         0xD,0x8,0xE,0xC,0x7,0x3,0x9,0xA,0x1,0x5,0x2,0x4,0x6,0xF,0x0,0xB,
         0xE,0x9,0xB,0x2,0x5,0xF,0x7,0x1,0x0,0xD,0xC,0x6,0xA,0x4,0x3,0x8,
         0x3,0xE,0x5,0x9,0x6,0x8,0x0,0xD,0xA,0xB,0x7,0xC,0x2,0x1,0xF,0x4,
         0x8,0xF,0x6,0xB,0x1,0x9,0xC,0x5,0xD,0x3,0x7,0xA,0x0,0xE,0x2,0x4,
         0x9,0xB,0xC,0x0,0x3,0x6,0x7,0x5,0x4,0x8,0xE,0xF,0x1,0xA,0x2,0xD,
         0xC,0x6,0x5,0x2,0xB,0x0,0x9,0xD,0x3,0xE,0x7,0xA,0xF,0x4,0x1,0x8
    };
    
    private static byte[] ESbox_A = {
         0x9,0x6,0x3,0x2,0x8,0xB,0x1,0x7,0xA,0x4,0xE,0xF,0xC,0x0,0xD,0x5,
         0x3,0x7,0xE,0x9,0x8,0xA,0xF,0x0,0x5,0x2,0x6,0xC,0xB,0x4,0xD,0x1,
         0xE,0x4,0x6,0x2,0xB,0x3,0xD,0x8,0xC,0xF,0x5,0xA,0x0,0x7,0x1,0x9,
         0xE,0x7,0xA,0xC,0xD,0x1,0x3,0x9,0x0,0x2,0xB,0x4,0xF,0x8,0x5,0x6,
         0xB,0x5,0x1,0x9,0x8,0xD,0xF,0x0,0xE,0x4,0x2,0x3,0xC,0x7,0xA,0x6,
         0x3,0xA,0xD,0xC,0x1,0x2,0x0,0xB,0x7,0x5,0x9,0x4,0x8,0xF,0xE,0x6,
         0x1,0xD,0x2,0x9,0x7,0xA,0x6,0x0,0x8,0xC,0x4,0x5,0xF,0x3,0xB,0xE,
         0xB,0xA,0xF,0x5,0x0,0xC,0xE,0x8,0x6,0x2,0x3,0x9,0x1,0x7,0xD,0x4
    };
    
    private static byte[] ESbox_B = {
         0x8,0x4,0xB,0x1,0x3,0x5,0x0,0x9,0x2,0xE,0xA,0xC,0xD,0x6,0x7,0xF,
         0x0,0x1,0x2,0xA,0x4,0xD,0x5,0xC,0x9,0x7,0x3,0xF,0xB,0x8,0x6,0xE,
         0xE,0xC,0x0,0xA,0x9,0x2,0xD,0xB,0x7,0x5,0x8,0xF,0x3,0x6,0x1,0x4,
         0x7,0x5,0x0,0xD,0xB,0x6,0x1,0x2,0x3,0xA,0xC,0xF,0x4,0xE,0x9,0x8,
         0x2,0x7,0xC,0xF,0x9,0x5,0xA,0xB,0x1,0x4,0x0,0xD,0x6,0x8,0xE,0x3,
         0x8,0x3,0x2,0x6,0x4,0xD,0xE,0xB,0xC,0x1,0x7,0xF,0xA,0x0,0x9,0x5,
         0x5,0x2,0xA,0xB,0x9,0x1,0xC,0x3,0x7,0x4,0xD,0x0,0x6,0xF,0x8,0xE,
         0x0,0x4,0xB,0xE,0x8,0x3,0x7,0x1,0xA,0x2,0x9,0x6,0xF,0xD,0x5,0xC
    };
    
    private static byte[] ESbox_C = {
         0x1,0xB,0xC,0x2,0x9,0xD,0x0,0xF,0x4,0x5,0x8,0xE,0xA,0x7,0x6,0x3,
         0x0,0x1,0x7,0xD,0xB,0x4,0x5,0x2,0x8,0xE,0xF,0xC,0x9,0xA,0x6,0x3,
         0x8,0x2,0x5,0x0,0x4,0x9,0xF,0xA,0x3,0x7,0xC,0xD,0x6,0xE,0x1,0xB,
         0x3,0x6,0x0,0x1,0x5,0xD,0xA,0x8,0xB,0x2,0x9,0x7,0xE,0xF,0xC,0x4,
         0x8,0xD,0xB,0x0,0x4,0x5,0x1,0x2,0x9,0x3,0xC,0xE,0x6,0xF,0xA,0x7,
         0xC,0x9,0xB,0x1,0x8,0xE,0x2,0x4,0x7,0x3,0x6,0x5,0xA,0x0,0xF,0xD,
         0xA,0x9,0x6,0x8,0xD,0xE,0x2,0x0,0xF,0x3,0x5,0xB,0x4,0x1,0xC,0x7,
         0x7,0x4,0x0,0x5,0xA,0x2,0xF,0xE,0xC,0x6,0x1,0xB,0xD,0x9,0x3,0x8
    };
    
    private static byte[] ESbox_D = {
         0xF,0xC,0x2,0xA,0x6,0x4,0x5,0x0,0x7,0x9,0xE,0xD,0x1,0xB,0x8,0x3,
         0xB,0x6,0x3,0x4,0xC,0xF,0xE,0x2,0x7,0xD,0x8,0x0,0x5,0xA,0x9,0x1,
         0x1,0xC,0xB,0x0,0xF,0xE,0x6,0x5,0xA,0xD,0x4,0x8,0x9,0x3,0x7,0x2,
         0x1,0x5,0xE,0xC,0xA,0x7,0x0,0xD,0x6,0x2,0xB,0x4,0x9,0x3,0xF,0x8,
         0x0,0xC,0x8,0x9,0xD,0x2,0xA,0xB,0x7,0x3,0x6,0x5,0x4,0xE,0xF,0x1,
         0x8,0x0,0xF,0x3,0x2,0x5,0xE,0xB,0x1,0xA,0x4,0x7,0xC,0x9,0xD,0x6,
         0x3,0x0,0x6,0xF,0x1,0xE,0x9,0x2,0xD,0x8,0xC,0x4,0xB,0xA,0x5,0x7,
         0x1,0xA,0x6,0x8,0xF,0xB,0x0,0x4,0xC,0x3,0x5,0x9,0x7,0xD,0x2,0xE
    };
    
    //S-box for digest
    private static byte DSbox_Test[] = {
         0x4,0xA,0x9,0x2,0xD,0x8,0x0,0xE,0x6,0xB,0x1,0xC,0x7,0xF,0x5,0x3,
         0xE,0xB,0x4,0xC,0x6,0xD,0xF,0xA,0x2,0x3,0x8,0x1,0x0,0x7,0x5,0x9,
         0x5,0x8,0x1,0xD,0xA,0x3,0x4,0x2,0xE,0xF,0xC,0x7,0x6,0x0,0x9,0xB,
         0x7,0xD,0xA,0x1,0x0,0x8,0x9,0xF,0xE,0x4,0x6,0xC,0xB,0x2,0x5,0x3,
         0x6,0xC,0x7,0x1,0x5,0xF,0xD,0x8,0x4,0xA,0x9,0xE,0x0,0x3,0xB,0x2,
         0x4,0xB,0xA,0x0,0x7,0x2,0x1,0xD,0x3,0x6,0x8,0x5,0x9,0xC,0xF,0xE,
         0xD,0xB,0x4,0x1,0x3,0xF,0x5,0x9,0x0,0xA,0xE,0x7,0x6,0x8,0x2,0xC,
         0x1,0xF,0xD,0x0,0x5,0x7,0xA,0x4,0x9,0x2,0x3,0xE,0x6,0xB,0x8,0xC
    };
    
    private static byte DSbox_A[] = {
         0xA,0x4,0x5,0x6,0x8,0x1,0x3,0x7,0xD,0xC,0xE,0x0,0x9,0x2,0xB,0xF,
         0x5,0xF,0x4,0x0,0x2,0xD,0xB,0x9,0x1,0x7,0x6,0x3,0xC,0xE,0xA,0x8,
         0x7,0xF,0xC,0xE,0x9,0x4,0x1,0x0,0x3,0xB,0x5,0x2,0x6,0xA,0x8,0xD,
         0x4,0xA,0x7,0xC,0x0,0xF,0x2,0x8,0xE,0x1,0x6,0x5,0xD,0xB,0x9,0x3,
         0x7,0x6,0x4,0xB,0x9,0xC,0x2,0xA,0x1,0x8,0x0,0xE,0xF,0xD,0x3,0x5,
         0x7,0x6,0x2,0x4,0xD,0x9,0xF,0x0,0xA,0x1,0x5,0xB,0x8,0xE,0xC,0x3,
         0xD,0xE,0x4,0x1,0x7,0x0,0x5,0xA,0x3,0xC,0x8,0xF,0x6,0x2,0x9,0xB,
         0x1,0x3,0xA,0x9,0x5,0xB,0x4,0xF,0x8,0x6,0x7,0xE,0xD,0x0,0x2,0xC
    };
    
    //
    // pre-defined sbox table
    //
    private static Hashtable sBoxes = new Hashtable();
    
    static
    {
        addSBox("Default", Sbox_Default);
        addSBox("E-TEST", ESbox_Test);
        addSBox("E-A", ESbox_A);
        addSBox("E-B", ESbox_B);
        addSBox("E-C", ESbox_C);
        addSBox("E-D", ESbox_D);
        addSBox("D-TEST", DSbox_Test);
        addSBox("D-A", DSbox_A);
    }

    private static void addSBox(String sBoxName, byte[] sBox)
    {
        sBoxes.put(Strings.toUpperCase(sBoxName), sBox);        
    }
    
    /**
     * standard constructor.
     */
    public GOST28147Engine()
    {
    }

    /**
     * initialise an GOST28147 cipher.
     *
     * @param forEncryption whether or not we are for encryption.
     * @param params the parameters required to set up the cipher.
     * @exception IllegalArgumentException if the params argument is
     * inappropriate.
     */
    public void init(
        boolean           forEncryption,
        CipherParameters  params)
    {
        if (params instanceof ParametersWithSBox)
        {
            ParametersWithSBox   param = (ParametersWithSBox)params;

            //
            // Set the S-Box
            //
            byte[] sBox = param.getSBox();
            if (sBox.length != Sbox_Default.length)
            {
                throw new IllegalArgumentException("invalid S-box passed to GOST28147 init");
            }
            this.S = Arrays.clone(sBox);

            //
            // set key if there is one
            //
            if (param.getParameters() != null)
            {
                workingKey = generateWorkingKey(forEncryption,
                        ((KeyParameter)param.getParameters()).getKey());
            }
        }
        else if (params instanceof KeyParameter)
        {
            workingKey = generateWorkingKey(forEncryption,
                                  ((KeyParameter)params).getKey());
        }
        else if (params != null)
        {
           throw new IllegalArgumentException("invalid parameter passed to GOST28147 init - " + params.getClass().getName());
        }
    }

    public String getAlgorithmName()
    {
        return "GOST28147";
    }

    public int getBlockSize()
    {
        return BLOCK_SIZE;
    }

    public int processBlock(
        byte[] in,
        int inOff,
        byte[] out,
        int outOff)
    {
        if (workingKey == null)
        {
            throw new IllegalStateException("GOST28147 engine not initialised");
        }

        if ((inOff + BLOCK_SIZE) > in.length)
        {
            throw new DataLengthException("input buffer too short");
        }

        if ((outOff + BLOCK_SIZE) > out.length)
        {
            throw new OutputLengthException("output buffer too short");
        }

        GOST28147Func(workingKey, in, inOff, out, outOff);

        return BLOCK_SIZE;
    }

    public void reset()
    {
    }

    private int[] generateWorkingKey(
        boolean forEncryption,
        byte[]  userKey)
    {
         this.forEncryption = forEncryption;

        if (userKey.length != 32)
        {
            throw new IllegalArgumentException("Key length invalid. Key needs to be 32 byte - 256 bit!!!");
        }

        int key[] = new int[8];
        for(int i=0; i!=8; i++)
        {
            key[i] = bytesToint(userKey,i*4);
        }

        return key;
    }

    private int GOST28147_mainStep(int n1, int key)
    {
        int cm = (key + n1); // CM1

        // S-box replacing

        int om = S[  0 + ((cm >> (0 * 4)) & 0xF)] << (0 * 4);
           om += S[ 16 + ((cm >> (1 * 4)) & 0xF)] << (1 * 4);
           om += S[ 32 + ((cm >> (2 * 4)) & 0xF)] << (2 * 4);
           om += S[ 48 + ((cm >> (3 * 4)) & 0xF)] << (3 * 4);
           om += S[ 64 + ((cm >> (4 * 4)) & 0xF)] << (4 * 4);
           om += S[ 80 + ((cm >> (5 * 4)) & 0xF)] << (5 * 4);
           om += S[ 96 + ((cm >> (6 * 4)) & 0xF)] << (6 * 4);
           om += S[112 + ((cm >> (7 * 4)) & 0xF)] << (7 * 4);

        return om << 11 | om >>> (32-11); // 11-leftshift
    }

    private void GOST28147Func(
        int[]   workingKey,
        byte[]  in,
        int     inOff,
        byte[]  out,
        int     outOff)
    {
        int N1, N2, tmp;  //tmp -> for saving N1
        N1 = bytesToint(in, inOff);
        N2 = bytesToint(in, inOff + 4);

        if (this.forEncryption)
        {
          for(int k = 0; k < 3; k++)  // 1-24 steps
          {
            for(int j = 0; j < 8; j++)
            {
                tmp = N1;
                N1 = N2 ^ GOST28147_mainStep(N1, workingKey[j]); // CM2
                N2 = tmp;
            }
          }
          for(int j = 7; j > 0; j--)  // 25-31 steps
          {
              tmp = N1;
              N1 = N2 ^ GOST28147_mainStep(N1, workingKey[j]); // CM2
              N2 = tmp;
          }
        }
        else //decrypt
        {
          for(int j = 0; j < 8; j++)  // 1-8 steps
          {
             tmp = N1;
             N1 = N2 ^ GOST28147_mainStep(N1, workingKey[j]); // CM2
             N2 = tmp;
          }
          for(int k = 0; k < 3; k++)  //9-31 steps
          {
            for(int j = 7; j >= 0; j--)
            {
                if ((k == 2) && (j==0))
                {
                    break; // break 32 step
                }
                tmp = N1;
                N1 = N2 ^ GOST28147_mainStep(N1, workingKey[j]); // CM2
                N2 = tmp;
            }
          }
        }

        N2 = N2 ^ GOST28147_mainStep(N1, workingKey[0]);  // 32 step (N1=N1)

        intTobytes(N1, out, outOff);
        intTobytes(N2, out, outOff + 4);
    }

    //array of bytes to type int
    private int bytesToint(
        byte[]  in,
        int     inOff)
    {
        return  ((in[inOff + 3] << 24) & 0xff000000) + ((in[inOff + 2] << 16) & 0xff0000) +
                ((in[inOff + 1] << 8) & 0xff00) + (in[inOff] & 0xff);
    }

    //int to array of bytes
    private void intTobytes(
            int     num,
            byte[]  out,
            int     outOff)
    {
            out[outOff + 3] = (byte)(num >>> 24);
            out[outOff + 2] = (byte)(num >>> 16);
            out[outOff + 1] = (byte)(num >>> 8);
            out[outOff] =     (byte)num;
    }
    
    /**
     * Return the S-Box associated with SBoxName
     * @param sBoxName name of the S-Box
     * @return byte array representing the S-Box
     */
    public static byte[] getSBox(
        String sBoxName)
    {
        byte[] sBox = (byte[])sBoxes.get(Strings.toUpperCase(sBoxName));

        if (sBox == null)
        {
            throw new IllegalArgumentException("Unknown S-Box - possible types: "
                + "\"Default\", \"E-Test\", \"E-A\", \"E-B\", \"E-C\", \"E-D\", \"D-Test\", \"D-A\".");
        }

        return Arrays.clone(sBox);
    }
}
