Question

我正在尝试用c ++实现基本的MD5算法。我主要遵循the wiki page's算法，这似乎很简单。但是，我现在一直在争夺一段时间。我没有获得空字符串的必需哈希值。我甚至已经到目前为止看到64轮中的每一轮都发生了什么，但无济于事。这就是我到目前为止所做的。代码没有经过优化或编写得特别好，但我刚刚将它们一起攻击，所以看看我是否在正确的轨道上。

#include "md5.h"
#include <iostream>
#include <iomanip>
#include <windows.h>

using namespace std;

unsigned int rotateL(unsigned int x, int n)
{
    return ((x) << n) | ((x) >> (32 - n));

}

int main()
{
//The required hash value using existing md5 algorithm

MD5 md5 ;
cout << "empty str is:" << endl;
puts( md5.digestString( "" ) ) ;


//Initialize Vars
unsigned int a = 0x67452301;
unsigned int b = 0xefcdab89;
unsigned int c = 0x98badcfe;
unsigned int d = 0x10325476;

//Make a copy of above
unsigned int A = a;
unsigned int B = b;
unsigned int C = c;
unsigned int D = d;


//Assuming an empty string ""
//The message would be appended with 1 and then padded with 0's
//so m = 10000....until 512 bits
//is this true?
unsigned int m[16] = {0x80000000, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
    , 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

int r[64] =  {7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22
    ,5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20
        ,4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23
        ,6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21};

unsigned int k[64] = { 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee
    ,0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501
        ,0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be
        ,0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821
        ,0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa
        ,0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8
        ,0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed
        ,0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a
        ,0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c
        ,0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70
        ,0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05
        ,0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665
        ,0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039
        ,0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1
        ,0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1
        ,0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 };


// Do an ititial Round just for testing...
unsigned int f = 0;
cout << "Doing round " << dec << 1 << endl;
f = (b & c) | ((~b) & d);   //round 1
cout << "f is " << hex << f << endl;
unsigned int temp = d;
d = c;
c = b;
int i = 0;
int g = 0;
cout << "k is " << hex << k[0] << endl;
cout << "r is " << dec << r[0] << endl;
b = b^(rotateL( a ^ f ^ k[0] ^ m[0] ,r[0]));
a = temp;

cout << "a is " << hex << a << endl;
cout << "b is " << hex << b << endl;
cout << "c is " << hex << c << endl;
cout << "d is " << hex << d << endl;

for (int i=1;i<16;i++){
    cout << "Doing round " << dec << i+1 << endl;
    f = (b & c) | ((~b) & d);   //round 1
    g = i;
    cout << "f is " << hex << f << endl;
    //res = d & b | ~d & c; //round 2

    unsigned int temp = d;
    d = c;
    c = b;
    cout << "k is " << hex << k[i] << endl;
    cout << "r is " << dec << r[i] << endl;
    b = b^(rotateL( a ^ f ^ k[i] ^ m[g] ,r[i]));
    a = temp;

    cout << "a is " << hex << a << endl;
    cout << "b is " << hex << b << endl;
    cout << "c is " << hex << c << endl;
    cout << "d is " << hex << d << endl;
    system("PAUSE");
}

for (int i=16;i<32;i++){
    cout << "Doing round " << dec << i+1 << endl;
    f = d & b | ~d & c; //round 2
    cout << "f is " << hex << f << endl;

    g = ((5*i)+1)%16;

    unsigned int temp = d;
    d = c;
    c = b;
    cout << "k is " << hex << k[i] << endl;
    cout << "r is " << dec << r[i] << endl;
    b = b^(rotateL( a ^ f ^ k[i] ^ m[g] ,r[i]));
    a = temp;

    cout << "a is " << hex << a << endl;
    cout << "b is " << hex << b << endl;
    cout << "c is " << hex << c << endl;
    cout << "d is " << hex << d << endl;
    system("PAUSE");
}


for (int i=32;i<48;i++){
    cout << "Doing round " << dec << i+1 << endl;
    f = b ^ c ^ d;
    cout << "f is " << hex << f << endl;

    g = ((3*i)+5)%16;

    unsigned int temp = d;
    d = c;
    c = b;
    cout << "k is " << hex << k[i] << endl;
    cout << "r is " << dec << r[i] << endl;
    b = b^(rotateL( a ^ f ^ k[i] ^ m[g] ,r[i]));
    a = temp;

    cout << "a is " << hex << a << endl;
    cout << "b is " << hex << b << endl;
    cout << "c is " << hex << c << endl;
    cout << "d is " << hex << d << endl;
    system("PAUSE");
}

for (int i=48;i<64;i++){
    cout << "Doing round " << dec << i+1 << endl;
    f = c ^ (b | ~ d);
    cout << "f is " << hex << f << endl;

    g = ((7*i))%16;

    unsigned int temp = d;
    d = c;
    c = b;
    cout << "k is " << hex << k[i] << endl;
    cout << "r is " << dec << r[i] << endl;
    b = b^(rotateL( a ^ f ^ k[i] ^ m[g] ,r[i]));
    a = temp;

    cout << "a is " << hex << a << endl;
    cout << "b is " << hex << b << endl;
    cout << "c is " << hex << c << endl;
    cout << "d is " << hex << d << endl;
    system("PAUSE");
}

A = A ^ a;
B = B ^ b;
C = C ^ c;
D = D ^ d;

cout << "Finally: " << endl;
cout << "A is " << hex << A << endl;
cout << "B is " << hex << B << endl;
cout << "D is " << hex << C << endl;
cout << "D is " << hex << D << endl;

//The above would now be appended but they 
//do not equal to the required hash! 
//So clearly it is wrong??


return 0;

}

我有一种感觉，也许我在填充阶段做错了但我无法弄明白。任何帮助将不胜感激！

Answer 1

这可能是您的问题之一：

for (int i=1;i<16;i++){

我认为“i”需要初始化为0而不是1.因为维基百科代码显示如下：

//Main loop:
    for i from 0 to 63
        if 0 ≤ i ≤ 15 then
            f := (b and c) or ((not b) and d)
            g := i

此外，当你在每一轮更新“b”时，你按如下方式实现它：

b = b^(rotateL( a ^ f ^ k[i] ^ m[g] ,r[i]));

但维基百科页面上的参考代码实现如下：

b := b + leftrotate((a + f + k[i] + w[g]) , r[i])

请注意，参考代码只是将所有这些值相加，您使用的是xor（^）运算符。

我怀疑还有其他问题，因此您可能需要使用参考代码仔细检查您的实现。

在c ++中实现基本的MD5算法

1 个答案: