MD5加密类

用户登陆案例，所有的用户名与密码是以明文的形式出现的那么就造成了一个不安全的隐患，因为如果数据库被黑了，则所有的信息也就可以看见了，所有为了保证数据的安全性，使用MD5加密，MD5是不可逆编码的。
MD5类的代码：
/*************************************************
md5 类实现了RSA Data Security, Inc.在提交给IETF
的RFC1321中的MD5 message-digest 算法。
*************************************************/

public class MD5 {
/* 下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的，
这里把它们实现成为static final是表示了只读，切能在同一个进程空间内的多个
Instance间共享*/
        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;

        static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 下面的三个成员是MD5计算过程中用到的3个核心数据，在原始的C实现中
           被定义到MD5_CTX结构中

         */
        private long[] state = new long[4];  // state (ABCD)
        private long[] count = new long[2];  // number of bits, modulo 2^64 (lsb first)
        private byte[] buffer = new byte[64]; // input buffer

/* digestHexStr是MD5的唯一一个公共成员，是最新一次计算结果的
　 16进制ASCII表示.
*/
        public String digestHexStr;

        /* digest,是最新一次计算结果的2进制内部表示，表示128bit的MD5值.
*/
        private byte[] digest = new byte[16];

/*
   getMD5ofStr是类MD5最主要的公共方法，入口参数是你想要进行MD5变换的字符串
   返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．
*/
        public String getMD5ofStr(String inbuf) {
                md5Init();
                md5Update(inbuf.getBytes(), inbuf.length());
                md5Final();
                digestHexStr = "";
                for (int i = 0; i < 16; i++) {
                        digestHexStr += byteHEX(digest[i]);
                }
                return digestHexStr;

        }
        // 这是MD5这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
        public MD5() {
                md5Init();

                return;
        }



        /* md5Init是一个初始化函数，初始化核心变量，装入标准的幻数 */
        private void md5Init() {
                count[0] = 0L;
                count[1] = 0L;
                ///* Load magic initialization constants.

                state[0] = 0x67452301L;
                state[1] = 0xefcdab89L;
                state[2] = 0x98badcfeL;
                state[3] = 0x10325476L;

                return;
        }
        /* F, G, H ,I 是4个基本的MD5函数，在原始的MD5的C实现中，由于它们是
        简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们
     　　实现成了private方法，名字保持了原来C中的。 */

        private long F(long x, long y, long z) {
                return (x & y) | ((~x) & z);

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

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

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

       /*
          FF,GG,HH和II将调用F,G,H,I进行近一步变换
          FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
          Rotation is separate from addition to prevent recomputation.
       */

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

        private long GG(long a, long b, long c, long d, long x, long s,
                long ac) {
                a += G (b, c, d) + x + ac;
                a = ((int) a << s) | ((int) a >>> (32 - s));
                a += b;
                return a;
        }
        private long HH(long a, long b, long c, long d, long x, long s,
                long ac) {
                a += H (b, c, d) + x + ac;
                a = ((int) a << s) | ((int) a >>> (32 - s));
                a += b;
                return a;
        }
        private long II(long a, long b, long c, long d, long x, long s,
                long ac) {
                a += I (b, c, d) + x + ac;
                a = ((int) a << s) | ((int) a >>> (32 - s));
                a += b;
                return a;
        }
        /*
         md5Update是MD5的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个
         函数由getMD5ofStr调用，调用之前需要调用md5init，因此把它设计成private的
        */
        private void md5Update(byte[] inbuf, int inputLen) {

                int i, index, partLen;
                byte[] block = new byte[64];
                index = (int)(count[0] >>> 3) & 0x3F;
                // /* Update number of bits */
                if ((count[0] += (inputLen << 3)) < (inputLen << 3))
                        count[1]++;
                count[1] += (inputLen >>> 29);

                partLen = 64 - index;

                // Transform as many times as possible.
                if (inputLen >= partLen) {
                        md5Memcpy(buffer, inbuf, index, 0, partLen);
                        md5Transform(buffer);

                        for (i = partLen; i + 63 < inputLen; i += 64) {

                                md5Memcpy(block, inbuf, 0, i, 64);
                                md5Transform (block);
                        }
                        index = 0;

                } else

                        i = 0;

                ///* Buffer remaining input */
                md5Memcpy(buffer, inbuf, index, i, inputLen - i);

        }

        /*
          md5Final整理和填写输出结果
        */
        private void md5Final () {
                byte[] bits = new byte[8];
                int index, padLen;

                ///* Save number of bits */
                Encode (bits, count,;

                ///* Pad out to 56 mod 64.
                index = (int)(count[0] >>> 3) & 0x3f;
                padLen = (index < 56) ? (56 - index) : (120 - index);
                md5Update (PADDING, padLen);

                ///* Append length (before padding) */
                md5Update(bits,;

                ///* Store state in digest */
                Encode (digest, state, 16);

        }

        /* md5Memcpy是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的
　　　　　 字节拷贝到output的outpos位置开始
        */

        private void md5Memcpy (byte[] output, byte[] input,
                int outpos, int inpos, int len)
        {
                int i;

                for (i = 0; i < len; i++)
                        output[outpos + i] = input[inpos + i];
        }

        /*
           md5Transform是MD5核心变换程序，有md5Update调用，block是分块的原始字节
        */
        private void md5Transform (byte block[]) {
                long a = state[0], b = state[1], c = state[2], d = state[3];
                long[] x = new long[16];

                Decode (x, block, 64);

                /* Round 1 */
                a = FF (a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */
                d = FF (d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */
                c = FF (c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */
                b = FF (b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */
                a = FF (a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */
                d = FF (d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */
                c = FF (c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */
                b = FF (b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */
                a = FF (a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */
                d = FF (d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */
                c = FF (c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */
                b = FF (b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */
                a = FF (a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */
                d = FF (d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */
                c = FF (c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */
                b = FF (b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */

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

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

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

                state[0] += a;
                state[1] += b;
                state[2] += c;
                state[3] += d;

        }

        /*Encode把long数组按顺序拆成byte数组，因为java的long类型是64bit的，
          只拆低32bit，以适应原始C实现的用途
        */
        private void Encode (byte[] output, long[] input, int len) {
                int i, j;

                for (i = 0, j = 0; j < len; i++, j += 4) {
                        output[j] = (byte)(input[i] & 0xffL);
                        output[j + 1] = (byte)((input[i] >>> & 0xffL);
                        output[j + 2] = (byte)((input[i] >>> 16) & 0xffL);
                        output[j + 3] = (byte)((input[i] >>> 24) & 0xffL);
                }
        }

        /*Decode把byte数组按顺序合成成long数组，因为java的long类型是64bit的，
          只合成低32bit，高32bit清零，以适应原始C实现的用途
        */
        private void Decode (long[] output, byte[] input, int len) {
                int i, j;


                for (i = 0, j = 0; j < len; i++, j += 4)
                        output[i] = b2iu(input[j]) |
                                (b2iu(input[j + 1]) << |
                                (b2iu(input[j + 2]) << 16) |
                                (b2iu(input[j + 3]) << 24);

                return;
        }

        /*
          b2iu是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
        */
        public static long b2iu(byte b) {
                return b < 0 ? b & 0x7F + 128 : b;
        }

/*byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示，
　因为java中的byte的toString无法实现这一点，我们又没有C语言中的
   sprintf(outbuf,"%02X",ib)
*/
        public static String byteHEX(byte ib) {
                char[] Digit = { '0','1','2','3','4','5','6','7','8','9',
                'A','B','C','D','E','F' };
                char [] ob = new char[2];
                ob[0] = Digit[(ib >>> 4) & 0X0F];
                ob[1] = Digit[ib & 0X0F];
                String s = new String(ob);
                return s;
        }
  public static void main(String args[])
     {
   MD5 md5=new MD5();
   System.out.println(md5.getMD5ofStr("haha"));
  }

}