c++实现MD5算法实现代码

测试结果和百度百科测试例子一致。

实现过程中需要注意事项：最后把四个变量A B C D 链接成结果时 ，注意变量高低位的先后顺序，具体参考 LinkResult（）方法。

md5.h

#ifndef _MD5_H_
#define _MD5_H_

#include <iostream>
#include <string>
using namespace std;

class MD5
{
  public:
    typedef unsigned char uchar8; //make sure it is 8bit
    typedef char char8; //make sure it is 8bit
    MD5();

    void init();

    void UpdateMd5(const uchar8 input[], const int length);
    void UpdateMd5(const char8 input[], const int length);   

    void Finalize();

    void ComputMd5(const uchar8 input[], const int length);
    void ComputMd5(const char8 input[], const int length); 

    string GetMd5();

    void printMd5();

  private:
    typedef unsigned int uint32;    //make sure it is 32 bit;
    typedef unsigned long long uint64; //make sure it is 64 bit;
    uint32 A, B, C, D;
    const static int blockLen_ = 64;  // 512/8
    //the remain after last updata (because md5 may be computed segment by segment)
    uchar8 remain_[blockLen_];
    int remainNum_ ;     // the number of remain_, < 64
    uint64 totalInputBits_;
    uchar8 md5Result_[16];  //bit style md5 result,totally 128 bit
    char md5Result_hex_[33]; //hexadecimal style result; md5Result_hex_[32]='\0'
    bool isDone_;      // indicate the comput is finished;

    inline uint32 RotateLeft(const uint32 x, int n);
    inline uint32 F(const uint32 x, const uint32 y, const uint32 z);
    inline uint32 G(const uint32 x, const uint32 y, const uint32 z);
    inline uint32 H(const uint32 x, const uint32 y, const uint32 z);
    inline uint32 I(const uint32 x, const uint32 y, const uint32 z);
    inline void FF(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
            const uint32 Mj, const int s, const uint32 ti);
    inline void GG(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
            const uint32 Mj, const int s, const uint32 ti);
    inline void HH(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
            const uint32 Mj, const int s, const uint32 ti);
    inline void II(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
            const uint32 Mj, const int s, const uint32 ti);

    void UcharToUint(uint32 output[], const uchar8 input[], const unsigned int transLength);

    void FourRound(const uchar8 block[]);  

    void LinkResult();

};

/* user guide
  you can comput the md5 by using the funtion ComputMd5
  eg:
    MD5 m;
    MD5::char8 str[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    m.ComputMd5(str,sizeof(str) - 1);
    m.printMd5();

  if you want to comput segment by segment,you can do as follow, and init() is suggested
  the begging,and Finalize() must call in the end:

    MD5 M;
    m.init();
    MD5::uchar8 str1[] = "ABCDEFGHIJKLMN";
    MD5::uchar8 str2[] = "OPQRSTUVWXYZabcdefghijk";
    MD5::uchar8 str3[] = "lmnopqrstuvwxyz";
    m.UpdateMd5(str1,sizeof(str1) - 1);
    m.UpdateMd5(str2,sizeof(str2) - 1);
    m.UpdateMd5(str3,sizeof(str3) - 1);
    m.Finalize();
    m.printMd5();

  if you want to comput the md5 of a file, you can use the interface of this program.
*/

#endif

md5.cpp

#include"md5.h"

#include<iostream>
using namespace std;

const int S[4][4] = {7, 12, 17, 22,
           5, 9, 14, 20,
           4, 11, 16, 23,
           6, 10, 15, 21};
void MD5::init()
{
  A = 0x67452301;
  B = 0xefcdab89;
  C = 0x98badcfe;
  D = 0x10325476;
  remainNum_ = 0;
  remain_[0] = '\0';
  md5Result_hex_[0] = '\0';
  md5Result_[0] = '\0';
  totalInputBits_ = 0;
  isDone_ = false;
}

MD5::MD5()
{
  init();
}

inline MD5::uint32 MD5::RotateLeft(const uint32 x, int n)
{
  return (x << n) | (x >> (32-n));
  // if x is signed, use: (x << n) | ((x & 0xFFFFFFFF) >> (32-n))
}
inline MD5::uint32 MD5::F(const uint32 x, const uint32 y, const uint32 z)
{
  return (x & y) | ((~x) & z);
}
inline MD5::uint32 MD5::G(const uint32 x, const uint32 y, const uint32 z)
{
  return (x & z) | (y & (~z));
}
inline MD5::uint32 MD5::H(const uint32 x, const uint32 y, const uint32 z)
{
  return x ^ y ^ z;
}
inline MD5::uint32 MD5::I(const uint32 x, const uint32 y, const uint32 z)
{
  return y ^ (x | (~z));
}

inline void MD5::FF(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
          const uint32 Mj, const int s, const uint32 ti)
{
  a = b + RotateLeft(a + F(b, c, d) + Mj + ti, s);
}
inline void MD5::GG(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
          const uint32 Mj, const int s, const uint32 ti)
{
  a = b + RotateLeft(a + G(b, c, d) + Mj + ti, s);
}
inline void MD5::HH(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
          const uint32 Mj, const int s, const uint32 ti)
{
  a = b + RotateLeft(a + H(b, c, d) + Mj + ti, s);
}
inline void MD5::II(uint32 &a, const uint32 b, const uint32 c, const uint32 d,
          const uint32 Mj, const int s, const uint32 ti)
{
  a = b + RotateLeft(a + I(b, c, d) + Mj + ti, s);
}     

// link A B C D to result(bit style result and hexadecimal style result)
void MD5::LinkResult()
{
  //bit style result
  for(int i = 0; i < 4; i++) //link A: low to high
  {
    md5Result_[i] = (A >> 8*i) & 0xff;
  }
  for(int i = 4; i<8; i++)  //link B: low to high
  {
    md5Result_[i] = (B >> 8*(i - 4)) & 0xff;
  }
  for(int i = 8; i<12; i++) //link C: low to high
  {
    md5Result_[i] = (C >> 8*(i - 8)) & 0xff;
  }
  for(int i = 12; i<16; i++) //link D: low to high
  {
    md5Result_[i] = (D >> 8*(i - 12)) & 0xff;
  }

  //change to hexadecimal style result
  // note: it is not the same as simply link hex(A) hex(B) hex(C) hex(D)
  for(int i = 0; i < 16; i++)
    sprintf(& md5Result_hex_[i*2], "%02x", md5Result_[i]);
  md5Result_hex_[32] = '\0';

}

//print the md5 by hex
void MD5::printMd5()
{
  if(!isDone_)
  {
    cout<< "Error: computation is not finished" <<endl;

  }
  else
    cout<< "MD5 Value: " << md5Result_hex_ <<endl;
}

//get the md5 value of hex style
string MD5::GetMd5()
{
  if(!isDone_)
  {
    cout<< "Error: computation is not finished" <<endl;
    exit(0);
  }
  string a((const char *)md5Result_hex_);
  return a;
}

void MD5::UcharToUint(uint32 output[], const uchar8 input[], const unsigned int transLength)
{
  for(int i = 0, j = 0; j < transLength; i++, j += 4)
  {
    output[i] = ((uint32)input[j]) | (((uint32)input[j+1]) << 8) |
        (((uint32)input[j+2]) << 16) | (((uint32)input[j+3]) << 24);
  }
}

// four round on a block of 512 bits;
void MD5::FourRound(const uchar8 block[])
{
  uint32 a = A, b = B, c = C, d = D;
  uint32 M[16];
  UcharToUint(M, block, blockLen_); //blockLen_ is a const int =64;

  //round 1
  FF (a, b, c, d, M[ 0], S[0][0], 0xd76aa478);
  FF (d, a, b, c, M[ 1], S[0][1], 0xe8c7b756);
  FF (c, d, a, b, M[ 2], S[0][2], 0x242070db);
  FF (b, c, d, a, M[ 3], S[0][3], 0xc1bdceee);
  FF (a, b, c, d, M[ 4], S[0][0], 0xf57c0faf);
  FF (d, a, b, c, M[ 5], S[0][1], 0x4787c62a);
  FF (c, d, a, b, M[ 6], S[0][2], 0xa8304613);
  FF (b, c, d, a, M[ 7], S[0][3], 0xfd469501);
  FF (a, b, c, d, M[ 8], S[0][0], 0x698098d8);
  FF (d, a, b, c, M[ 9], S[0][1], 0x8b44f7af);
  FF (c, d, a, b, M[10], S[0][2], 0xffff5bb1);
  FF (b, c, d, a, M[11], S[0][3], 0x895cd7be);
  FF (a, b, c, d, M[12], S[0][0], 0x6b901122);
  FF (d, a, b, c, M[13], S[0][1], 0xfd987193);
  FF (c, d, a, b, M[14], S[0][2], 0xa679438e);
  FF (b, c, d, a, M[15], S[0][3], 0x49b40821); 

  // round 2
  GG (a, b, c, d, M[ 1], S[1][0], 0xf61e2562);
  GG (d, a, b, c, M[ 6], S[1][1], 0xc040b340);
  GG (c, d, a, b, M[11], S[1][2], 0x265e5a51);
  GG (b, c, d, a, M[ 0], S[1][3], 0xe9b6c7aa);
  GG (a, b, c, d, M[ 5], S[1][0], 0xd62f105d);
  GG (d, a, b, c, M[10], S[1][1], 0x2441453);
  GG (c, d, a, b, M[15], S[1][2], 0xd8a1e681);
  GG (b, c, d, a, M[ 4], S[1][3], 0xe7d3fbc8);
  GG (a, b, c, d, M[ 9], S[1][0], 0x21e1cde6);
  GG (d, a, b, c, M[14], S[1][1], 0xc33707d6);
  GG (c, d, a, b, M[ 3], S[1][2], 0xf4d50d87);
  GG (b, c, d, a, M[ 8], S[1][3], 0x455a14ed);
  GG (a, b, c, d, M[13], S[1][0], 0xa9e3e905);
  GG (d, a, b, c, M[ 2], S[1][1], 0xfcefa3f8);
  GG (c, d, a, b, M[ 7], S[1][2], 0x676f02d9);
  GG (b, c, d, a, M[12], S[1][3], 0x8d2a4c8a);

  //round 3
  HH (a, b, c, d, M[ 5], S[2][0], 0xfffa3942);
  HH (d, a, b, c, M[ 8], S[2][1], 0x8771f681);
  HH (c, d, a, b, M[11], S[2][2], 0x6d9d6122);
  HH (b, c, d, a, M[14], S[2][3], 0xfde5380c);
  HH (a, b, c, d, M[ 1], S[2][0], 0xa4beea44);
  HH (d, a, b, c, M[ 4], S[2][1], 0x4bdecfa9);
  HH (c, d, a, b, M[ 7], S[2][2], 0xf6bb4b60);
  HH (b, c, d, a, M[10], S[2][3], 0xbebfbc70);
  HH (a, b, c, d, M[13], S[2][0], 0x289b7ec6);
  HH (d, a, b, c, M[ 0], S[2][1], 0xeaa127fa);
  HH (c, d, a, b, M[ 3], S[2][2], 0xd4ef3085);
  HH (b, c, d, a, M[ 6], S[2][3], 0x4881d05);
  HH (a, b, c, d, M[ 9], S[2][0], 0xd9d4d039);
  HH (d, a, b, c, M[12], S[2][1], 0xe6db99e5);
  HH (c, d, a, b, M[15], S[2][2], 0x1fa27cf8);
  HH (b, c, d, a, M[ 2], S[2][3], 0xc4ac5665); 

  //round 4
  II (a, b, c, d, M[ 0], S[3][0], 0xf4292244);
  II (d, a, b, c, M[ 7], S[3][1], 0x432aff97);
  II (c, d, a, b, M[14], S[3][2], 0xab9423a7);
  II (b, c, d, a, M[ 5], S[3][3], 0xfc93a039);
  II (a, b, c, d, M[12], S[3][0], 0x655b59c3);
  II (d, a, b, c, M[ 3], S[3][1], 0x8f0ccc92);
  II (c, d, a, b, M[10], S[3][2], 0xffeff47d);
  II (b, c, d, a, M[ 1], S[3][3], 0x85845dd1);
  II (a, b, c, d, M[ 8], S[3][0], 0x6fa87e4f);
  II (d, a, b, c, M[15], S[3][1], 0xfe2ce6e0);
  II (c, d, a, b, M[ 6], S[3][2], 0xa3014314);
  II (b, c, d, a, M[13], S[3][3], 0x4e0811a1);
  II (a, b, c, d, M[ 4], S[3][0], 0xf7537e82);
  II (d, a, b, c, M[11], S[3][1], 0xbd3af235);
  II (c, d, a, b, M[ 2], S[3][2], 0x2ad7d2bb);
  II (b, c, d, a, M[ 9], S[3][3], 0xeb86d391); 

  A += a;
  B += b;
  C += c;
  D += d;
}

// update md5,must consider the remain_.
void MD5::UpdateMd5(const uchar8 input[], const int length)
{
  isDone_ = false;
  totalInputBits_ += (length << 3);

  int start = blockLen_ - remainNum_; //blockLen_ = 64
  //copy a part of input to remain_ so it can form a block(size=64)

  if(start <= length)
  {
    // can form a block,then do FourRound to this block
      memcpy(&remain_[remainNum_], input, start) ;
      FourRound(remain_);

      int i;
      for(i = start; i <= length - blockLen_; i += blockLen_)
      {
        FourRound(&input[i]);
      }
      remainNum_ = length - i;
      memcpy(remain_, &input[i], remainNum_);
  }
  else
  {
    // can not form a block, function return;
    memcpy(&remain_[remainNum_], input, length);
    remainNum_ += length;
  }  

}

void MD5::UpdateMd5(const char8 input[], const int length)
{
  UpdateMd5((const uchar8 *)input, length);
}

// padding with 100000... to remain_ and add the 64bit original size of input
void MD5::Finalize()
{
  if(isDone_ == true)
    return;

  uchar8 padding[64] = {
  0x80, 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
  };

  int temp = 56 - remainNum_; //56 = 448/8
  if(temp > 0)
  {
    UpdateMd5(padding, temp);
    totalInputBits_ -= (temp << 3);
  }
  else if(temp < 0)
  {
    UpdateMd5(padding, 64 + temp);
    totalInputBits_ -= ((64 + temp) << 3);
  }

  // trans totalInputBits_ to uchar8 (64bits)
  uchar8 Bits[8];
  for(int i = 0; i < 8; i++)
  {
    Bits[i] = (totalInputBits_ >> 8*i) & 0xff;
  }

  UpdateMd5(Bits, 8); // add the number of original input (the last 64bits)

  LinkResult();
  isDone_ = true;
}

// comput the md5 based on input, (just this one input)
void MD5::ComputMd5(const uchar8 input[], const int length)
{
  init();
  UpdateMd5(input, length);
  Finalize();
}

void MD5::ComputMd5(const char8 input[], const int length)
{
  ComputMd5((const uchar8 *)input, length);
}