[转载]MD5算法之C#程序 MD5算法描述[2]

[abcd  4  6 61]  [dabc 11 10 62]  [cdab  2 15 63]  [bcda  9 21 64]

/* 然后进行如下操作 */
a = a + aa
b = b + bb
c = c + cc
d = d + dd

next i /* 结束对i的循环*/

第六步，输出结果。
a，b，c，d连续存放，共16个字节，128位。按十六进制依次输出这个16个字节。

最后，用程序语言实现算法后，可以输入以下几个信息对程序作一个简单的测试，
看看程序有没有错误。
　md5 ("") = d41d8cd98f00b204e9800998ecf8427e
　md5 ("a") = 0cc175b9c0f1b6a831c399e269772661
　md5 ("abc") = 900150983cd24fb0d6963f7d28e17f72
　md5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0
　md5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b
　md5 ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789") =
d174ab98d277d9f5a5611c2c9f419d9f
  md5 ("123456789012345678901234567890123456789012345678901234567890123456789
01234567890") = 57edf4a22be3c955ac49da2e2107b67a

md5算法之c#程序

md5算法比较特别，最适合用汇编语言来写，好多高级语言对之无能无力或效率极低。
比如我最开始尝试用python和euphoria编写，发现不太容易。相比而言，c#作为c家簇
中新兴的一门.net语言，功能比较全面。花了一晚上的工夫终于用c#最先实现了md5。
主要是由于对算法的一些细节不太注意，结果输出总是不对，调试了好长时间。

[code]
//源文件：md5.cs
// md5 alogrithm
// by rufi 2004.6.20 http://rufi.yculblog.com/
using system;
using system.collections;
using system.io;

public class md5 {
  //static state variables
  private static uint32 a;
  private static uint32 b;
  private static uint32 c;
  private static uint32 d;

  //number of bits to rotate in tranforming
  private const int  s11 = 7;
  private const int  s12 = 12;
  private const int  s13 = 17;
  private const int  s14 = 22;
  private const int  s21 = 5;
  private const int  s22 = 9;
  private const int  s23 = 14;
  private const int  s24 = 20;
  private const int  s31 = 4;
  private const int  s32 = 11;
  private const int  s33 = 16;
  private const int  s34 = 23;
  private const int  s41 = 6;
  private const int  s42 = 10;
  private const int  s43 = 15;
  private const int  s44 = 21;

  /* f, g, h and i are basic md5 functions.
   * 四个非线性函数:
   *
   * f(x,y,z) =(x&y)|((~x)&z)
   * g(x,y,z) =(x&z)|(y&(~z))
   * h(x,y,z) =x^y^z
   * i(x,y,z)=y^(x|(~z))
   *
   * （&与，|或，~非，^异或）
   */
  private static uint32 f(uint32 x,uint32 y,uint32 z){
    return (x&y)|((~x)&z);
  }
  private static uint32 g(uint32 x,uint32 y,uint32 z){
    return (x&z)|(y&(~z));
  }
  private static uint32 h(uint32 x,uint32 y,uint32 z){
    return x^y^z;
  }
  private static uint32 i(uint32 x,uint32 y,uint32 z){
    return y^(x|(~z));
  }

  /* ff, gg, hh, and ii transformations for rounds 1, 2, 3, and 4.
   * rotation is separate from addition to prevent recomputation.
   */
  private static void ff(ref uint32 a,uint32 b,uint32 c,uint32 d,uint32 mj,int s,uint32 ti){
    a = a + f(b,c,d) + mj + ti;
    a = a << s | a >> (32-s);
    a += b;
  }
  private static void gg(ref uint32 a,uint32 b,uint32 c,uint32 d,uint32 mj,int s,uint32 ti){
    a = a + g(b,c,d) + mj + ti;
    a = a << s | a >> (32-s);
    a += b;
  }
  private static void hh(ref uint32 a,uint32 b,uint32 c,uint32 d,uint32 mj,int s,uint32 ti){
    a = a + h(b,c,d) + mj + ti;
    a = a << s | a >> (32-s);
    a += b;
  }
  private static void ii(ref uint32 a,uint32 b,uint32 c,uint32 d,uint32 mj,int s,uint32 ti){
    a = a + i(b,c,d) + mj + ti;
    a = a << s | a >> (32-s);
    a += b;
  }

  private static void md5_init(){
    a=0x67452301;  //in memory, this is 0x01234567
    b=0xefcdab89;  //in memory, this is 0x89abcdef
    c=0x98badcfe;  //in memory, this is 0xfedcba98
    d=0x10325476;  //in memory, this is 0x76543210
  }

  private static uint32[] md5_append(byte[] input){
    int zeros=0;
    int ones =1;
    int size=0;
    int n = input.length;
    int m = n%64;
    if( m < 56 ){
      zeros = 55-m;