MD5相关知识
JAVA
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MD5相关知识

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////////////////////////////////////////*
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;

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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;

1
/* 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;

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}
// 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。 /*/

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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
/*/

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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 md5 = new MD5();
System.out.println(md5.getMD5ofStr(“admin”));
}
}

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本文链接：https://royalscholar.cn/2017/02/08/MD5相关知识/

# JAVA, MD5

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