descipher.java

用Java语言编写的数据传输小软件 基于P2P传输模式 可以多线程传送 类似于QQ 速度和QQ差不多

package des;

/**
 *  DESCipher.java
 */
import java.io.*;

public class DESCipher {
    // Initial
    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 };

    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 };

    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 };

    final int[] INVP = { 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 };

    public byte[] cipher(byte[] theMsg, byte[][] subKeys, String mode)
            throws Exception {
        if (theMsg.length < 8){
            throw new Exception("Message is less than 64 bits.");
        }
        
        theMsg = selectBits(theMsg, IP); // Initial Permutation
        int blockSize = IP.length;
        byte[] l = selectBits(theMsg, 0, blockSize / 2);
        byte[] r = selectBits(theMsg, blockSize / 2, blockSize / 2);
        int numOfSubKeys = subKeys.length;
        for (int k = 0; k < numOfSubKeys; k++) {
            byte[] rBackup = r;
            r = selectBits(r, E); // Expansion
            if (mode.equalsIgnoreCase("encrypt"))
                r = doXORBytes(r, subKeys[k]); // XOR with the sub key
            else
                r = doXORBytes(r, subKeys[numOfSubKeys - k - 1]);
            r = substitution6x4(r); // Substitution
            r = selectBits(r, P); // Permutation
            r = doXORBytes(l, r); // XOR with the previous left half
            l = rBackup; // Taking the previous right half
        }
        byte[] lr = concatenateBits(r, blockSize / 2, l, blockSize / 2);
        lr = selectBits(lr, INVP); // Inverse Permutation
        return lr;
    }
    
    /**
     * Function: Do XOR between byte[] a and byte[] b
     * 
     * @param a
     * @param b
     * @return the result byte[]
     */
    private byte[] doXORBytes(byte[] a, byte[] b) {
        byte[] out = new byte[a.length];
        for (int i = 0; i < a.length; i++) {
            out[i] = (byte) (a[i] ^ b[i]);
        }
        return out;
    }

    /* INITIALIZE THE S TABLES */
    final int[] S = { 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, 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13,// S1
            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,// S2
            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, // S3
            5, 10, 14, 7, 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12,
            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,// S4
            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,// S5
            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, 4, 11, 2, 14, 15, 0, 8, 13, // S6
            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,// S7
            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 // S8
    };

    /**
     * Function: Substitution the 6-bit blocks by 4-bit blocks
     * 
     * @param in
     * @return byte[] that has been substituted.
     */
    public byte[] substitution6x4(byte[] in) {
        in = splitBytes(in, 6); // Splitting byte[] into 6-bit blocks
        byte[] out = new byte[in.length / 2];
        int lhByte = 0;
        for (int b = 0; b < in.length; b++) { // Should be sub-blocks
            byte valByte = in[b];
            int r = 2 * (valByte >> 7 & 0x0001) + (valByte >> 2 & 0x0001); // 1
            // and
            // 6
            int c = valByte >> 3 & 0x000F; // Middle 4 bits
            int hByte = S[64 * b + 16 * r + c]; // 4 bits (half byte) output
            if (b % 2 == 0)
                lhByte = hByte; // Left half byte
            else
                out[b / 2] = (byte) (16 * lhByte + hByte);
        }
        return out;
    }

    /**
     * Function: Split byte[] into len-bit blocks
     * 
     * @param in
     * @param len
     * @return byte[] that has been splited
     */
    private byte[] splitBytes(byte[] in, int len) {
        int numOfBytes = (8 * in.length - 1) / len + 1;
        byte[] out = new byte[numOfBytes];
        for (int i = 0; i < numOfBytes; i++) {
            for (int j = 0; j < len; j++) {
                int val = getBit(in, len * i + j);
                setBit(out, 8 * i + j, val);
            }
        }
        return out;
    }

    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 };

    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 };

    final int[] SHIFTS = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };

    public byte[][] getSubkeys(byte[] theKey) throws Exception {
        int activeKeySize = PC1.length;
        int numOfSubKeys = SHIFTS.length;
        byte[] activeKey = selectBits(theKey, PC1);
        int halfKeySize = activeKeySize / 2;
        byte[] c = selectBits(activeKey, 0, halfKeySize);
        byte[] d = selectBits(activeKey, halfKeySize, halfKeySize);
        byte[][] subKeys = new byte[numOfSubKeys][];
        for (int k = 0; k < numOfSubKeys; k++) {
            c = rotateLeft(c, halfKeySize, SHIFTS[k]);
            d = rotateLeft(d, halfKeySize, SHIFTS[k]);
            byte[] cd = concatenateBits(c, halfKeySize, d, halfKeySize);
            subKeys[k] = selectBits(cd, PC2);
        }
        return subKeys;
    }

    private byte[] rotateLeft(byte[] in, int len, int step) {
        int numOfBytes = (len - 1) / 8 + 1;
        byte[] out = new byte[numOfBytes];
        for (int i = 0; i < len; i++) {
            int val = getBit(in, (i + step) % len);
            setBit(out, i, val);
        }
        return out;
    }

    private byte[] concatenateBits(byte[] a, int aLen, byte[] b, int bLen) {
        int numOfBytes = (aLen + bLen - 1) / 8 + 1;
        byte[] out = new byte[numOfBytes];
        int j = 0;
        for (int i = 0; i < aLen; i++) {
            int val = getBit(a, i);
            setBit(out, j, val);
            j++;
        }
        for (int i = 0; i < bLen; i++) {
            int val = getBit(b, i);
            setBit(out, j, val);
            j++;
        }
        return out;
    }

    private byte[] selectBits(byte[] in, int pos, int len) {
        int numOfBytes = (len - 1) / 8 + 1;
        byte[] out = new byte[numOfBytes];
        for (int i = 0; i < len; i++) {
            int val = getBit(in, pos + i);
            setBit(out, i, val);
        }
        return out;
    }

    /**
     * Function: Get byte[] reversed from byte[] using map
     * 
     * @param in
     * @param map
     * @return the result byte[] reversed using map
     */
    private byte[] selectBits(byte[] in, int[] map) {
        int numOfBytes = (map.length - 1) / 8 + 1;
        byte[] out = new byte[numOfBytes];
        for (int i = 0; i < map.length; i++) {
            int val = getBit(in, map[i] - 1);
            setBit(out, i, val);
        }
        return out;
    }

    /**
     * Function: Get byte[]'s bit at position 'pos'
     * 
     * @param data
     * @param pos
     * @return the wanted bit
     */
    private int getBit(byte[] data, int pos) {
        int posByte = pos / 8;
        int posBit = pos % 8;
        byte valByte = data[posByte];
        int valInt = valByte >> (8 - (posBit + 1)) & 0x0001;
        return valInt;
    }

    /**
     * Function: Set byte[]'s bit at position 'pos' to val
     * 
     * @param data
     * @param pos
     * @param val
     */
    private void setBit(byte[] data, int pos, int val) {
        int posByte = pos / 8;
        int posBit = pos % 8;
        byte oldByte = data[posByte];
        oldByte = (byte) (((0xFF7F >> posBit) & oldByte) & 0x00FF);
        byte newByte = (byte) ((val << (8 - (posBit + 1))) | oldByte);
        data[posByte] = newByte;
    }


}