java中实现MD5加密

package Com.cs;

/*******************************************************************************
* md5 类实现了RSA Data Security, Inc.在提交给IETF 的RFC1321中的MD5 message-digest 算法。
******************************************************************************/
import java.lang.reflect.*;


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，且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, 8);

    // /* 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, 8);

    // /* 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] >>> 8) & 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]) << 8)
       | (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 m = new MD5();
    if (Array.getLength(args) == 0) { // 如果没有参数，执行标准的Test Suite

     System.out.println("MD5 Test suite:");
     System.out.println("MD5(""""):" + m.getMD5ofStr(""));
     System.out.println("MD5(""a""):" + m.getMD5ofStr("a"));
     System.out.println("MD5(""abc""):" + m.getMD5ofStr("abc"));
     System.out.println("MD5(""HelloWorld""):" + m.getMD5ofStr("HelloWorld"));
     System.out.println("MD5(""message digest""):"
       + m.getMD5ofStr("message digest"));
     System.out.println("MD5(""abcdefghijklmnopqrstuvwxyz""):"
       + m.getMD5ofStr("abcdefghijklmnopqrstuvwxyz"));
     System.out
       .println("MD5(""ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789""):"
         + m
           .getMD5ofStr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"));
    } else
     System.out
       .println("MD5(" + args[0] + ")=" + m.getMD5ofStr(args[0]));

}

}