[C#] - MD5 加密的具体流程

来源:http://www.chinaitpower.com/A/2005-05-13/116840.html

 

  1.来历
  MD5的全称是message-digest algorithm 5(信息-摘要算法,在90年代初由mit laboratory for computer science和rsa data security inc的ronald l. rivest开发出来,经md2、md3和md4发展而来。http://www.ietf.org/rfc/rfc1321.txt,是一份最权威的文档,由ronald l. rivest在1992年8月向ieft提交。
  
  2.用途
  MD5的作用是对一段信息(message)生成信息摘要(message-digest),该摘要对该信息具有唯一性,可以作为数字签名。用于验证文件的有效性(是否有丢失或损坏的数据),对用户密码的加密,在哈希函数中计算散列值
  
  3.特点
  输入一个任意长度的字节串,生成一个128位的整数。由于算法的某些不可逆特征,在加密应用上有较好的安全性。并且,MD5算法的使用不需要支付任何版权费用。
  
  4.说明
  唯一性和不可逆性都不是绝对的,从理论上分析是一种多对一的关系,但两个不同的信息产生相同摘要的概率很小。不可逆是指从输出反推输入所需的运算量和计算时间太大,使用穷搜字典的方法又需要太多的存储空间。
  
  5.算法描述
  
  算法输入是一个字节串,每个字节是8个bit.
  算法的执行分为以下几个步骤:
  
  第一步,补位:
  MD5算法先对输入的数据进行补位,使得数据的长度(以byte为单位)对64求余的结果是56。即数据扩展至LEN=K*64+56个字节,K为整数。
  补位方法:补一个1,然后补0至满足上述要求。相当于补一个0x80的字节,再补值为0的字节。这一步里总共补充的字节数为0~63个。
  
  第二步,附加数据长度:
  用一个64位的整数表示数据的原始长度(以bit为单位),将这个数字的8个字节按低位的在前,高位在后的顺序附加在补位后的数据后面。这时,数据被填补后的总长度为:
   LEN = K*64+56+8=(K+1)*64 Bytes。


  ※注意那个64位整数是输入数据的原始长度而不是填充字节后的长度,我就在这里栽了跟头.
  
  第三步,初始化MD5参数:
  有四个32位整数变量 (A,B,C,D) 用来计算信息摘要,每一个变量被初始化成以下以十六进制数表示的数值,低位的字节在前面。
   word A: 01 23 45 67
   word B: 89 ab cd ef
   word C: fe dc ba 98
   word D: 76 54 32 10
  ※注意低位的字节在前面指的是Little Endian平台上内存中字节的排列方式,而在程序中书写时,要写成:
   A=0x67452301
   B=0xefcdab89
   C=0x98badcfe
   D=0x10325476
  
  第四步,定义四个MD5基本的按位操作函数:
  X,Y,Z为32位整数。
   F(X,Y,Z) = (X and Y) or (not(X) and Z)
   G(X,Y,Z) = (X and Z) or (Y and not(Z))
   H(X,Y,Z) = X xor Y xor Z
   I(X,Y,Z) = Y xor (X or not(Z))
  
  再定义四个分别用于四轮变换的函数。
  设Mj表示消息的第j个子分组(从0到15),<<<s表示循环左移s位,则四种操作为:
   FF(a,b,c,d,Mj,s,ti)表示a=b+((a+(F(b,c,d)+Mj+ti)<<<s)
   GG(a,b,c,d,Mj,s,ti)表示a=b+((a+(G(b,c,d)+Mj+ti)<<<s)
   HH(a,b,c,d,Mj,s,ti)表示a=b+((a+(H(b,c,d)+Mj+ti)<<<s)
   II(a,b,c,d,Mj,s,ti)表示a=b+((a+(I(b,c,d)+Mj+ti)<<<s)
  
  
  第五步,对输入数据作变换。
  处理数据,N是总的字节数,以64个字节为一组,每组作一次循环,每次循环进行四轮操作。要变换的64个字节用16个32位的整数数组M[0 ...15]表示。而数组T[1 ... 64]表示一组常数, T[i]为4294967296*abs(sin(i))的32位整数部分,i的单位是弧度,i的取值从1到64。
  具体过程如下:

 

  
    
   /* 设置主循环变量 */
  For i
= 0 to N / 16 - 1 do
  
  
/* 每循环一次,把数据原文存放在16个元素的数组X中. */
  For j
= 0 to 15 do
  Set X[j] to M[i
* 16 + j].
  end
/ 结束对J的循环
  
  
/* Save A as AA, B as BB, C as CC, and D as DD.
  
*/
  AA
= A
  BB
= B
  CC
= C
  DD
= D
  
  
/* 第1轮 */
  
/* 以 [abcd k s i]表示如下操作
  a = b + ((a + F(b,c,d) + X[k] + T[i]) <<< s).
*/
  
/* Do the following 16 operations. */
  [ABCD 
0   7   1 ] [DABC  1 12   2 ] [CDAB  2 17   3 ] [BCDA  3 22   4 ]
  [ABCD 
4   7   5 ] [DABC  5 12   6 ] [CDAB  6 17   7 ] [BCDA  7 22   8 ]
  [ABCD 
8   7   9 ] [DABC  9 12 10 ] [CDAB 10 17 11 ] [BCDA 11 22 12 ]
  [ABCD
12   7 13 ] [DABC 13 12 14 ] [CDAB 14 17 15 ] [BCDA 15 22 16 ]
  
  
  
/* 第2轮* */
  
/* 以 [abcd k s i]表示如下操作
  a = b + ((a + G(b,c,d) + X[k] + T[i]) <<< s).
*/
  
/* Do the following 16 operations. */
  [ABCD 
1   5 17 ] [DABC  6   9 18 ] [CDAB 11 14 19 ] [BCDA  0 20 20 ]
  [ABCD 
5   5 21 ] [DABC 10   9 22 ] [CDAB 15 14 23 ] [BCDA  4 20 24 ]
  [ABCD 
9   5 25 ] [DABC 14   9 26 ] [CDAB  3 14 27 ] [BCDA  8 20 28 ]
  [ABCD
13   5 29 ] [DABC  2   9 30 ] [CDAB  7 14 31 ] [BCDA 12 20 32 ]
  
  
/* 第3轮 */
  
/* 以 [abcd k s i]表示如下操作
  a = b + ((a + H(b,c,d) + X[k] + T[i]) <<< s).
*/
  
/* Do the following 16 operations. */
  [ABCD 
5   4 33 ] [DABC  8 11 34 ] [CDAB 11 16 35 ] [BCDA 14 23 36 ]
  [ABCD 
1   4 37 ] [DABC  4 11 38 ] [CDAB  7 16 39 ] [BCDA 10 23 40 ]
  [ABCD
13   4 41 ] [DABC  0 11 42 ] [CDAB  3 16 43 ] [BCDA  6 23 44 ]
  [ABCD 
9   4 45 ] [DABC 12 11 46 ] [CDAB 15 16 47 ] [BCDA  2 23 48 ]
  
  
  
/* 第4轮 */
  
/* 以 [abcd k s i]表示如下操作
  a = b + ((a + I(b,c,d) + X[k] + T[i]) <<< s).
*/
  
/* Do the following 16 operations. */
  [ABCD 
0   6 49 ] [DABC  7 10 50 ] [CDAB 14 15 51 ] [BCDA  5 21 52 ]
  [ABCD
12   6 53 ] [DABC  3 10 54 ] [CDAB 10 15 55 ] [BCDA  1 21 56 ]
  [ABCD 
8   6 57 ] [DABC 15 10 58 ] [CDAB  6 15 59 ] [BCDA 13 21 60 ]
  [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 ("12345678901234567890123456789012345678901234567890123456789012345678901234567890") = 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。

 

  
    

// 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;
size
= n - m + 64 ;
}
else if (m == 56 )
{
zeros
= 0 ;
ones
= 0 ;
size
= n + 8 ;
}
else
{
zeros
= 63 - m + 56 ;
size
= n + 64 - m + 64 ;
}

ArrayList bs
= new ArrayList(input);
if (ones == 1 )
{
bs.Add((
byte ) 0x80 ); // 0x80 = $10000000
}
for ( int i = 0 ; i < zeros; i ++ )
{
bs.Add((
byte ) 0 );
}

UInt64 N
= (UInt64)n * 8 ;
byte h1 = ( byte )(N & 0xFF );
byte h2 = ( byte )((N >> 8 ) & 0xFF );
byte h3 = ( byte )((N >> 16 ) & 0xFF );
byte h4 = ( byte )((N >> 24 ) & 0xFF );
byte h5 = ( byte )((N >> 32 ) & 0xFF );
byte h6 = ( byte )((N >> 40 ) & 0xFF );
byte h7 = ( byte )((N >> 48 ) & 0xFF );
byte h8 = ( byte )(N >> 56 );
bs.Add(h1);
bs.Add(h2);
bs.Add(h3);
bs.Add(h4);
bs.Add(h5);
bs.Add(h6);
bs.Add(h7);
bs.Add(h8);
byte [] ts = ( byte [])bs.ToArray( typeof ( byte ));

/* Decodes input (byte[]) into output (UInt32[]). Assumes len is
* a multiple of 4.
*/
UInt32[] output
= new UInt32[size / 4 ];
for (Int64 i = 0 , j = 0 ; i < size; j ++ , i += 4 )
{
output[j]
= (UInt32)(ts[i] | ts[i + 1 ] << 8 | ts[i + 2 ] << 16 | ts[i + 3 ] << 24 );
}
return output;
}
private static UInt32[] MD5_Trasform(UInt32[] x)
{

UInt32 a, b, c, d;

for ( int k = 0 ; k < x.Length; k += 16 )
{
a
= A;
b
= B;
c
= C;
d
= D;

/* Round 1 */
FF(
ref a, b, c, d, x[k + 0 ], S11, 0xd76aa478 ); /* 1 */
FF(
ref d, a, b, c, x[k + 1 ], S12, 0xe8c7b756 ); /* 2 */
FF(
ref c, d, a, b, x[k + 2 ], S13, 0x242070db ); /* 3 */
FF(
ref b, c, d, a, x[k + 3 ], S14, 0xc1bdceee ); /* 4 */
FF(
ref a, b, c, d, x[k + 4 ], S11, 0xf57c0faf ); /* 5 */
FF(
ref d, a, b, c, x[k + 5 ], S12, 0x4787c62a ); /* 6 */
FF(
ref c, d, a, b, x[k + 6 ], S13, 0xa8304613 ); /* 7 */
FF(
ref b, c, d, a, x[k + 7 ], S14, 0xfd469501 ); /* 8 */
FF(
ref a, b, c, d, x[k + 8 ], S11, 0x698098d8 ); /* 9 */
FF(
ref d, a, b, c, x[k + 9 ], S12, 0x8b44f7af ); /* 10 */
FF(
ref c, d, a, b, x[k + 10 ], S13, 0xffff5bb1 ); /* 11 */
FF(
ref b, c, d, a, x[k + 11 ], S14, 0x895cd7be ); /* 12 */
FF(
ref a, b, c, d, x[k + 12 ], S11, 0x6b901122 ); /* 13 */
FF(
ref d, a, b, c, x[k + 13 ], S12, 0xfd987193 ); /* 14 */
FF(
ref c, d, a, b, x[k + 14 ], S13, 0xa679438e ); /* 15 */
FF(
ref b, c, d, a, x[k + 15 ], S14, 0x49b40821 ); /* 16 */

/* Round 2 */
GG(
ref a, b, c, d, x[k + 1 ], S21, 0xf61e2562 ); /* 17 */
GG(
ref d, a, b, c, x[k + 6 ], S22, 0xc040b340 ); /* 18 */
GG(
ref c, d, a, b, x[k + 11 ], S23, 0x265e5a51 ); /* 19 */
GG(
ref b, c, d, a, x[k + 0 ], S24, 0xe9b6c7aa ); /* 20 */
GG(
ref a, b, c, d, x[k + 5 ], S21, 0xd62f105d ); /* 21 */
GG(
ref d, a, b, c, x[k + 10 ], S22, 0x2441453 ); /* 22 */
GG(
ref c, d, a, b, x[k + 15 ], S23, 0xd8a1e681 ); /* 23 */
GG(
ref b, c, d, a, x[k + 4 ], S24, 0xe7d3fbc8 ); /* 24 */
GG(
ref a, b, c, d, x[k + 9 ], S21, 0x21e1cde6 ); /* 25 */
GG(
ref d, a, b, c, x[k + 14 ], S22, 0xc33707d6 ); /* 26 */
GG(
ref c, d, a, b, x[k + 3 ], S23, 0xf4d50d87 ); /* 27 */
GG(
ref b, c, d, a, x[k + 8 ], S24, 0x455a14ed ); /* 28 */
GG(
ref a, b, c, d, x[k + 13 ], S21, 0xa9e3e905 ); /* 29 */
GG(
ref d, a, b, c, x[k + 2 ], S22, 0xfcefa3f8 ); /* 30 */
GG(
ref c, d, a, b, x[k + 7 ], S23, 0x676f02d9 ); /* 31 */
GG(
ref b, c, d, a, x[k + 12 ], S24, 0x8d2a4c8a ); /* 32 */

/* Round 3 */
HH(
ref a, b, c, d, x[k + 5 ], S31, 0xfffa3942 ); /* 33 */
HH(
ref d, a, b, c, x[k + 8 ], S32, 0x8771f681 ); /* 34 */
HH(
ref c, d, a, b, x[k + 11 ], S33, 0x6d9d6122 ); /* 35 */
HH(
ref b, c, d, a, x[k + 14 ], S34, 0xfde5380c ); /* 36 */
HH(
ref a, b, c, d, x[k + 1 ], S31, 0xa4beea44 ); /* 37 */
HH(
ref d, a, b, c, x[k + 4 ], S32, 0x4bdecfa9 ); /* 38 */
HH(
ref c, d, a, b, x[k + 7 ], S33, 0xf6bb4b60 ); /* 39 */
HH(
ref b, c, d, a, x[k + 10 ], S34, 0xbebfbc70 ); /* 40 */
HH(
ref a, b, c, d, x[k + 13 ], S31, 0x289b7ec6 ); /* 41 */
HH(
ref d, a, b, c, x[k + 0 ], S32, 0xeaa127fa ); /* 42 */
HH(
ref c, d, a, b, x[k + 3 ], S33, 0xd4ef3085 ); /* 43 */
HH(
ref b, c, d, a, x[k + 6 ], S34, 0x4881d05 ); /* 44 */
HH(
ref a, b, c, d, x[k + 9 ], S31, 0xd9d4d039 ); /* 45 */
HH(
ref d, a, b, c, x[k + 12 ], S32, 0xe6db99e5 ); /* 46 */
HH(
ref c, d, a, b, x[k + 15 ], S33, 0x1fa27cf8 ); /* 47 */
HH(
ref b, c, d, a, x[k + 2 ], S34, 0xc4ac5665 ); /* 48 */

/* Round 4 */
II(
ref a, b, c, d, x[k + 0 ], S41, 0xf4292244 ); /* 49 */
II(
ref d, a, b, c, x[k + 7 ], S42, 0x432aff97 ); /* 50 */
II(
ref c, d, a, b, x[k + 14 ], S43, 0xab9423a7 ); /* 51 */
II(
ref b, c, d, a, x[k + 5 ], S44, 0xfc93a039 ); /* 52 */
II(
ref a, b, c, d, x[k + 12 ], S41, 0x655b59c3 ); /* 53 */
II(
ref d, a, b, c, x[k + 3 ], S42, 0x8f0ccc92 ); /* 54 */
II(
ref c, d, a, b, x[k + 10 ], S43, 0xffeff47d ); /* 55 */
II(
ref b, c, d, a, x[k + 1 ], S44, 0x85845dd1 ); /* 56 */
II(
ref a, b, c, d, x[k + 8 ], S41, 0x6fa87e4f ); /* 57 */
II(
ref d, a, b, c, x[k + 15 ], S42, 0xfe2ce6e0 ); /* 58 */
II(
ref c, d, a, b, x[k + 6 ], S43, 0xa3014314 ); /* 59 */
II(
ref b, c, d, a, x[k + 13 ], S44, 0x4e0811a1 ); /* 60 */
II(
ref a, b, c, d, x[k + 4 ], S41, 0xf7537e82 ); /* 61 */
II(
ref d, a, b, c, x[k + 11 ], S42, 0xbd3af235 ); /* 62 */
II(
ref c, d, a, b, x[k + 2 ], S43, 0x2ad7d2bb ); /* 63 */
II(
ref b, c, d, a, x[k + 9 ], S44, 0xeb86d391 ); /* 64 */

A
+= a;
B
+= b;
C
+= c;
D
+= d;
}
return new UInt32[] { A, B, C, D };
}
public static byte [] MD5Array( byte [] input)
{
MD5_Init();
UInt32[] block
= MD5_Append(input);
UInt32[] bits
= MD5_Trasform(block);

/* Encodes bits (UInt32[]) into output (byte[]). Assumes len is
* a multiple of 4.
*/
byte [] output = new byte [bits.Length * 4 ];
for ( int i = 0 , j = 0 ; i < bits.Length; i ++ , j += 4 )
{
output[j]
= ( byte )(bits[i] & 0xff );
output[j
+ 1 ] = ( byte )((bits[i] >> 8 ) & 0xff );
output[j
+ 2 ] = ( byte )((bits[i] >> 16 ) & 0xff );
output[j
+ 3 ] = ( byte )((bits[i] >> 24 ) & 0xff );
}
return output;
}

public static string ArrayToHexString( byte [] array, bool uppercase)
{
string hexString = "" ;
string format = " x2 " ;
if (uppercase)
{
format
= " X2 " ;
}
foreach ( byte b in array)
{
hexString
+= b.ToString(format);
}
return hexString;
}

public static string MDString( string message)
{
char [] c = message.ToCharArray();
byte [] b = new byte [c.Length];
for ( int i = 0 ; i < c.Length; i ++ )
{
b[i]
= ( byte )c[i];
}
byte [] digest = MD5Array(b);
return ArrayToHexString(digest, false );
}
public static string MDFile( string fileName)
{
FileStream fs
= File.Open(fileName, FileMode.Open, FileAccess.Read);
byte [] array = new byte [fs.Length];
fs.Read(array,
0 , ( int )fs.Length);
byte [] digest = MD5Array(array);
fs.Close();
return ArrayToHexString(digest, false );
}

public static string Test( string message)
{
return " rnMD5 ( " + message + " ) = " + MD5.MDString(message);
}
static void Main( string [] args)
{
Console.WriteLine(Test(
"" ));
Console.WriteLine();
Console.WriteLine(Test(
" a " ));
Console.WriteLine();
Console.WriteLine(Test(
" abc " ));
Console.WriteLine();
Console.WriteLine(Test(
" message digest " ));
Console.WriteLine();
Console.WriteLine(Test(
" abcdefghijklmnopqrstuvwxyz " ));
Console.WriteLine();
Console.WriteLine(Test(
" ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 " ));
Console.WriteLine();
Console.WriteLine(Test(
" 12345678901234567890123456789012345678901234567890123456789012345678901234567890 " ));
Console.ReadLine();
}
}

 

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