MD5加密算法

今天,因为要用到一个加密的过程,所以参照了一些网络上的内容,写了这个md5算法

package com.change.date;
/**
*Description: MD5加密算法
*
*Copyright: Copyright (c) 2005
*
*Company:  leemenz
*
* @author    李国庆
* @version   1.0.0.0
*/
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);
 }
 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 & 0xffL);
  output[j + 1] = (byte)((input >>> 8) & 0xffL);
  output[j + 2] = (byte)((input >>> 16) & 0xffL);
  output[j + 3] = (byte)((input >>> 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 = 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 String toMD5(String source){
 MD5 md5 = new MD5();
 return md5.getMD5ofStr(source);
}
}
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