MD5加密算法原理(含代码)以及SHA算法相关信息

package com.md5Impl;

public class MD5 {

    static final String hexs[] = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F"};
    //下面这些S11-S44实际上是一个4*4的矩阵，在四轮循环运算中用到
    static final int S11 = 7;
    static final int S12 = 12;
    static final int S13 = 17;
    static final int S14 = 22;
    static final int S21 = 5;
    static final int S22 = 9;
    static final int S23 = 14;
    static final int S24 = 20;
    static final int S31 = 4;
    static final int S32 = 11;
    static final int S33 = 16;
    static final int S34 = 23;
    static final int S41 = 6;
    static final int S42 = 10;
    static final int S43 = 15;
    static final int S44 = 21;
    //标准的幻数
    private static final long A = 0x67452301L;
    private static final long B = 0xefcdab89L;
    private static final long C = 0x98badcfeL;
    private static final long D = 0x10325476L;
    //java不支持无符号的基本数据（unsigned）
    private long[] result = {A, B, C, D};//存储hash结果，共4×32=128位，初始化值为（幻数的级联）

    public static void main(String[] args) {
        MD5 md = new MD5();
//        System.out.println("md5(abc)=" + md.digest("abc"));
        System.out.println("md5(abc)=" + md.digest("qwe"));
    }

    /**
     * 从inputBytes的index开始取512位，作为新的分组
     * 将每一个512位的分组再细分成16个小组，每个小组64位（8个字节）
     *
     * @param inputBytes
     * @param index
     * @return
     */
    private static long[] divGroup(byte[] inputBytes, int index) {
        long[] temp = new long[16];
        for (int i = 0; i < 16; i++) {
            temp[i] = b2iu(inputBytes[4 * i + index]) |
                    (b2iu(inputBytes[4 * i + 1 + index])) << 8 |
                    (b2iu(inputBytes[4 * i + 2 + index])) << 16 |
                    (b2iu(inputBytes[4 * i + 3 + index])) << 24;
        }
        return temp;
    }

    /**
     * 这时不存在符号位（符号位存储不再是代表正负），所以需要处理一下
     *
     * @param b
     * @return
     */
    public static long b2iu(byte b) {
        return b < 0 ? b & 0x7F + 128 : b;
    }

    /**
     * 下面是处理要用到的线性函数
     */
    private static long F(long x, long y, long z) {
        return (x & y) | ((~x) & z);
    }

    private static long G(long x, long y, long z) {
        return (x & z) | (y & (~z));
    }

    private static long H(long x, long y, long z) {
        return x ^ y ^ z;
    }

    private static long I(long x, long y, long z) {
        return y ^ (x | (~z));
    }

    private static long FF(long a, long b, long c, long d, long x, long s,
                           long ac) {
        a += (F(b, c, d) & 0xFFFFFFFFL) + x + ac;
        a = ((a & 0xFFFFFFFFL) << s) | ((a & 0xFFFFFFFFL) >>> (32 - s));
        a += b;
        return (a & 0xFFFFFFFFL);
    }

    private static long GG(long a, long b, long c, long d, long x, long s,
                           long ac) {
        a += (G(b, c, d) & 0xFFFFFFFFL) + x + ac;
        a = ((a & 0xFFFFFFFFL) << s) | ((a & 0xFFFFFFFFL) >>> (32 - s));
        a += b;
        return (a & 0xFFFFFFFFL);
    }

    private static long HH(long a, long b, long c, long d, long x, long s,
                           long ac) {
        a += (H(b, c, d) & 0xFFFFFFFFL) + x + ac;
        a = ((a & 0xFFFFFFFFL) << s) | ((a & 0xFFFFFFFFL) >>> (32 - s));
        a += b;
        return (a & 0xFFFFFFFFL);
    }

    private static long II(long a, long b, long c, long d, long x, long s,
                           long ac) {
        a += (I(b, c, d) & 0xFFFFFFFFL) + x + ac;
        a = ((a & 0xFFFFFFFFL) << s) | ((a & 0xFFFFFFFFL) >>> (32 - s));
        a += b;
        return (a & 0xFFFFFFFFL);
    }

    private String digest(String inputStr) {
        byte[] inputBytes = inputStr.getBytes();
        int byteLen = inputBytes.length;//长度（字节）
        int groupCount = 0;//完整分组的个数
        groupCount = byteLen / 64;//每组512位（64字节）
        long[] groups = null;//每个小组(64字节)再细分后的16个小组(4字节)

        //处理每一个完整的分组
        for (int step = 0; step < groupCount; step++) {
            groups = divGroup(inputBytes, step * 64);
            trans(groups);//处理分组，核心算法
        }

        //处理完整分组后的尾巴
        int rest = byteLen % 64;//512位分组后的余数
        byte[] tempBytes = new byte[64];
        if (rest <= 56) {
            for (int i = 0; i < rest; i++)
                tempBytes[i] = inputBytes[byteLen - rest + i];
            if (rest < 56) {
                tempBytes[rest] = (byte) (1 << 7);
                for (int i = 1; i < 56 - rest; i++)
                    tempBytes[rest + i] = 0;
            }
            long len = (long) (byteLen << 3);
            for (int i = 0; i < 8; i++) {
                tempBytes[56 + i] = (byte) (len & 0xFFL);
                len = len >> 8;
            }
            groups = divGroup(tempBytes, 0);
            trans(groups);//处理分组
        } else {
            for (int i = 0; i < rest; i++)
                tempBytes[i] = inputBytes[byteLen - rest + i];
            tempBytes[rest] = (byte) (1 << 7);
            for (int i = rest + 1; i < 64; i++)
                tempBytes[i] = 0;
            groups = divGroup(tempBytes, 0);
            trans(groups);//处理分组

            for (int i = 0; i < 56; i++)
                tempBytes[i] = 0;
            long len = (long) (byteLen << 3);
            for (int i = 0; i < 8; i++) {
                tempBytes[56 + i] = (byte) (len & 0xFFL);
                len = len >> 8;
            }
            groups = divGroup(tempBytes, 0);
            trans(groups);//处理分组
        }

        //将Hash值转换成十六进制的字符串
        String resStr = "";
        long temp = 0;
        for (int i = 0; i < 4; i++) {
            for (int j = 0; j < 4; j++) {
                temp = result[i] & 0x0FL;
                String a = hexs[(int) (temp)];
                result[i] = result[i] >> 4;
                temp = result[i] & 0x0FL;
                resStr += hexs[(int) (temp)] + a;
                result[i] = result[i] >> 4;
            }
        }
        return resStr;
    }

    /**
     * 主要的操作，四轮循环
     *
     * @param groups[]--每一个分组512位（64字节）
     */
    private void trans(long[] groups) {
        long a = result[0], b = result[1], c = result[2], d = result[3];
        /*第一轮*/
        a = FF(a, b, c, d, groups[0], S11, 0xd76aa478L); /* 1 */
        d = FF(d, a, b, c, groups[1], S12, 0xe8c7b756L); /* 2 */
        c = FF(c, d, a, b, groups[2], S13, 0x242070dbL); /* 3 */
        b = FF(b, c, d, a, groups[3], S14, 0xc1bdceeeL); /* 4 */
        a = FF(a, b, c, d, groups[4], S11, 0xf57c0fafL); /* 5 */
        d = FF(d, a, b, c, groups[5], S12, 0x4787c62aL); /* 6 */
        c = FF(c, d, a, b, groups[6], S13, 0xa8304613L); /* 7 */
        b = FF(b, c, d, a, groups[7], S14, 0xfd469501L); /* 8 */
        a = FF(a, b, c, d, groups[8], S11, 0x698098d8L); /* 9 */
        d = FF(d, a, b, c, groups[9], S12, 0x8b44f7afL); /* 10 */
        c = FF(c, d, a, b, groups[10], S13, 0xffff5bb1L); /* 11 */
        b = FF(b, c, d, a, groups[11], S14, 0x895cd7beL); /* 12 */
        a = FF(a, b, c, d, groups[12], S11, 0x6b901122L); /* 13 */
        d = FF(d, a, b, c, groups[13], S12, 0xfd987193L); /* 14 */
        c = FF(c, d, a, b, groups[14], S13, 0xa679438eL); /* 15 */
        b = FF(b, c, d, a, groups[15], S14, 0x49b40821L); /* 16 */

        /*第二轮*/
        a = GG(a, b, c, d, groups[1], S21, 0xf61e2562L); /* 17 */
        d = GG(d, a, b, c, groups[6], S22, 0xc040b340L); /* 18 */
        c = GG(c, d, a, b, groups[11], S23, 0x265e5a51L); /* 19 */
        b = GG(b, c, d, a, groups[0], S24, 0xe9b6c7aaL); /* 20 */
        a = GG(a, b, c, d, groups[5], S21, 0xd62f105dL); /* 21 */
        d = GG(d, a, b, c, groups[10], S22, 0x2441453L); /* 22 */
        c = GG(c, d, a, b, groups[15], S23, 0xd8a1e681L); /* 23 */
        b = GG(b, c, d, a, groups[4], S24, 0xe7d3fbc8L); /* 24 */
        a = GG(a, b, c, d, groups[9], S21, 0x21e1cde6L); /* 25 */
        d = GG(d, a, b, c, groups[14], S22, 0xc33707d6L); /* 26 */
        c = GG(c, d, a, b, groups[3], S23, 0xf4d50d87L); /* 27 */
        b = GG(b, c, d, a, groups[8], S24, 0x455a14edL); /* 28 */
        a = GG(a, b, c, d, groups[13], S21, 0xa9e3e905L); /* 29 */
        d = GG(d, a, b, c, groups[2], S22, 0xfcefa3f8L); /* 30 */
        c = GG(c, d, a, b, groups[7], S23, 0x676f02d9L); /* 31 */
        b = GG(b, c, d, a, groups[12], S24, 0x8d2a4c8aL); /* 32 */

        /*第三轮*/
        a = HH(a, b, c, d, groups[5], S31, 0xfffa3942L); /* 33 */
        d = HH(d, a, b, c, groups[8], S32, 0x8771f681L); /* 34 */
        c = HH(c, d, a, b, groups[11], S33, 0x6d9d6122L); /* 35 */
        b = HH(b, c, d, a, groups[14], S34, 0xfde5380cL); /* 36 */
        a = HH(a, b, c, d, groups[1], S31, 0xa4beea44L); /* 37 */
        d = HH(d, a, b, c, groups[4], S32, 0x4bdecfa9L); /* 38 */
        c = HH(c, d, a, b, groups[7], S33, 0xf6bb4b60L); /* 39 */
        b = HH(b, c, d, a, groups[10], S34, 0xbebfbc70L); /* 40 */
        a = HH(a, b, c, d, groups[13], S31, 0x289b7ec6L); /* 41 */
        d = HH(d, a, b, c, groups[0], S32, 0xeaa127faL); /* 42 */
        c = HH(c, d, a, b, groups[3], S33, 0xd4ef3085L); /* 43 */
        b = HH(b, c, d, a, groups[6], S34, 0x4881d05L); /* 44 */
        a = HH(a, b, c, d, groups[9], S31, 0xd9d4d039L); /* 45 */
        d = HH(d, a, b, c, groups[12], S32, 0xe6db99e5L); /* 46 */
        c = HH(c, d, a, b, groups[15], S33, 0x1fa27cf8L); /* 47 */
        b = HH(b, c, d, a, groups[2], S34, 0xc4ac5665L); /* 48 */

        /*第四轮*/
        a = II(a, b, c, d, groups[0], S41, 0xf4292244L); /* 49 */
        d = II(d, a, b, c, groups[7], S42, 0x432aff97L); /* 50 */
        c = II(c, d, a, b, groups[14], S43, 0xab9423a7L); /* 51 */
        b = II(b, c, d, a, groups[5], S44, 0xfc93a039L); /* 52 */
        a = II(a, b, c, d, groups[12], S41, 0x655b59c3L); /* 53 */
        d = II(d, a, b, c, groups[3], S42, 0x8f0ccc92L); /* 54 */
        c = II(c, d, a, b, groups[10], S43, 0xffeff47dL); /* 55 */
        b = II(b, c, d, a, groups[1], S44, 0x85845dd1L); /* 56 */
        a = II(a, b, c, d, groups[8], S41, 0x6fa87e4fL); /* 57 */
        d = II(d, a, b, c, groups[15], S42, 0xfe2ce6e0L); /* 58 */
        c = II(c, d, a, b, groups[6], S43, 0xa3014314L); /* 59 */
        b = II(b, c, d, a, groups[13], S44, 0x4e0811a1L); /* 60 */
        a = II(a, b, c, d, groups[4], S41, 0xf7537e82L); /* 61 */
        d = II(d, a, b, c, groups[11], S42, 0xbd3af235L); /* 62 */
        c = II(c, d, a, b, groups[2], S43, 0x2ad7d2bbL); /* 63 */
        b = II(b, c, d, a, groups[9], S44, 0xeb86d391L); /* 64 */

        /*加入到之前计算的结果当中*/
        result[0] += a;
        result[1] += b;
        result[2] += c;
        result[3] += d;
        result[0] = result[0] & 0xFFFFFFFFL;
        result[1] = result[1] & 0xFFFFFFFFL;
        result[2] = result[2] & 0xFFFFFFFFL;
        result[3] = result[3] & 0xFFFFFFFFL;
    }

}

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