Use Windows Crypto API to calculate a MD5 string.

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Introduction

The source code demonstrates how to invoke the Windows Crypto API to calculate a MD5 string.

The MD5 Message-Digest Algorithm is described in Internet RFC 132.

The sample uses the class Cmd5Capi, a very simple MFC class to wrap the standard win api necesary calls.

Includes required

#include <wincrypt.h> // Cryptographic API Prototypes and Definitions

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Victor M. Valenzuela

Web Developer

Spain

Member

Now, I works for Aurigae S.A a spanish services enterprise, specialized on information technologies for critical mission applications, mainly in the areas of payment system management, stock trading and telecommunications.

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Thanks

Asaf G

0:05 6 May '08

A simple example on how to use the CryptoAPI, just what I needed.
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How to decrypt data?

ivax

0:49 4 Oct '05

In my app, I need to decrypt data from a Password field in order to compare with Original Data. How can I do?
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Re: How to decrypt data?

John A. Johnson

0:06 26 Oct '05

md5 is well known as an irreversible method, or almost quite difficult to be reversible.
This way you can ensure privacy and security because there is no way to "reverse" the stored string.

For this reason, the approach must different,in the code you don’t have to "decode", but, "code" the inputted data.

so, to explain the concept, this is a wrong way:

if (szFromGUIPass == DeCode(szStoredPass))
{
...
}

this must be the solution

if (Code(szFromGUIPass) == szStoredPass)
{
...
}

A better solution : here is the code

Elmue

10:43 22 Apr '04

Hello

Your code has one big problem :
It takes only a string as input.
No more compiler errors !
(And your code is written in MFC and is not usable without modifications in a project (e.g. bad error handling))

But if you need the MD5 of a file and the file is 3 Gigabyte of size you will not be able to load the file into a string !
For that you need an algorithm that is capable to calculate from multiple smaller blocks of the file.

I attach a reusable C++ class (without MFC) which performs this task with highest speed !

After you are ready destroy the MD5 class or call FreeBuffer();

Header :
___________________________________________________________

// cMD5.h: interface for the cMD5 class.

#if !defined(AFX_CMD5_H__6C2F7C61_93D8_11D8_A8BA_000AE637F271__INCLUDED_)
#define AFX_CMD5_H__6C2F7C61_93D8_11D8_A8BA_000AE637F271__INCLUDED_
 
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#define _ReadBufSize 1000000
 
class cMD5  
{
public:
    char* CalcMD5FromString(const char *s8_Input);
    char* CalcMD5FromFile  (const char *s8_Path);
 
    void FreeBuffer();
    cMD5();
    virtual ~cMD5();
 
private:
    struct MD5Context 
    {
        unsigned long buf[4];
        unsigned long bits[2];
        unsigned char in[64];
    };
 
    void MD5Init();
    void MD5Update(unsigned char *buf, unsigned len);
    void MD5Final (unsigned char digest[16]);
    
    void MD5Transform(unsigned long buf[4], unsigned long in[16]);
    char* MD5FinalToString();
    
    void byteReverse (unsigned char *buf, unsigned longs);
 
    char *mp_s8ReadBuffer;
    MD5Context ctx;
    char   ms8_MD5[40]; // Output buffer
};
 
#endif // !defined(AFX_CMD5_H__6C2F7C61_93D8_11D8_A8BA_000AE637F271__INCLUDED_)

_______________________________________________________

and the cpp file :

________________________________________________________

#include "cMD5.h"
 
#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif
 

cMD5::cMD5()
{
    // don't alloc buffer here, only on request
    mp_s8ReadBuffer = 0;
}
 
cMD5::~cMD5()
{
    FreeBuffer();
}
 
void cMD5::FreeBuffer()
{
    if (mp_s8ReadBuffer) delete mp_s8ReadBuffer;
}
 
/*********************************************************************
//
//         calculate MD5 from a file of any size (also size = 0)
//         returns "" on file error
//
/********************************************************************/
 
char* cMD5::CalcMD5FromFile(const char *s8_Path)
{
    if (!mp_s8ReadBuffer) mp_s8ReadBuffer = new char[_ReadBufSize];
 
    MD5Init();
 
    // ++++++++++++ Read file block by block +++++++++++

    HANDLE h_File = CreateFile(s8_Path, GENERIC_READ, FILE_SHARE_READ, 0, 
                               OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
        
    if (h_File == INVALID_HANDLE_VALUE)
        return "";
 
    int s32_Size = GetFileSize(h_File, 0);
 
    while (s32_Size > 0)
    {
        unsigned long u32_Read = 0;
        if (!ReadFile(h_File, mp_s8ReadBuffer, _ReadBufSize, &u32_Read, 0))
        {
            CloseHandle(h_File);
            return "";
        }
 
        MD5Update((unsigned char*)mp_s8ReadBuffer, u32_Read);
 
        s32_Size -= u32_Read;
    };
 
    CloseHandle(h_File);
 
    // ++++++++++++ Signature --> String +++++++++++

    return MD5FinalToString();
}
 

/*********************************************************************
//
//                calculate MD5 from a string
//
/********************************************************************/
 

char* cMD5::CalcMD5FromString(const char *s8_Input)
{
    MD5Init();
    MD5Update((unsigned char*)s8_Input, strlen(s8_Input));
 
    return MD5FinalToString();
}
 

/*********************************************************************
//
//                           Calculation functions
//
/*********************************************************************
/*
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void cMD5::MD5Init()
{
    ctx.buf[0] = 0x67452301;
    ctx.buf[1] = 0xefcdab89;
    ctx.buf[2] = 0x98badcfe;
    ctx.buf[3] = 0x10325476;
 
    ctx.bits[0] = 0;
    ctx.bits[1] = 0;
}
 
/*
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void cMD5::MD5Update(unsigned char *buf, unsigned len)
{
    unsigned long t;
 
    /* Update bitcount */
 
    t = ctx.bits[0];
    if ((ctx.bits[0] = t + ((unsigned long) len << 3)) < t)
    ctx.bits[1]++;  /* Carry from low to high */
    ctx.bits[1] += len >> 29;
 
    t = (t >> 3) & 0x3f;    /* Bytes already in shsInfo->data */
 
    /* Handle any leading odd-sized chunks */
 
    if (t) {
    unsigned char *p = (unsigned char *) ctx.in + t;
 
    t = 64 - t;
    if (len < t) {
        memcpy(p, buf, len);
        return;
    }
    memcpy(p, buf, t);
    cMD5::byteReverse(ctx.in, 16);
    MD5Transform(ctx.buf, (unsigned long *) ctx.in);
    buf += t;
    len -= t;
    }
    /* Process data in 64-byte chunks */
 
    while (len >= 64) {
    memcpy(ctx.in, buf, 64);
    cMD5::byteReverse(ctx.in, 16);
    MD5Transform(ctx.buf, (unsigned long *) ctx.in);
    buf += 64;
    len -= 64;
    }
 
    /* Handle any remaining bytes of data. */
 
    memcpy(ctx.in, buf, len);
}
 

/*
 * Convert signature to CString
 */
char* cMD5::MD5FinalToString()
{
    unsigned char signature[16];
    MD5Final(signature);
 
    ms8_MD5[0] = 0;
    char s8_Temp[5];
    for (int i=0; i<16; i++) 
    {
        sprintf(s8_Temp, "%02X", signature[i]);
        strcat(ms8_MD5, s8_Temp);
    }
 
    return ms8_MD5;
}
 

/*
 * Final wrapup - pad to 64-byte boundary with the bit pattern 
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void cMD5::MD5Final(unsigned char digest[16])
{
    unsigned count;
    unsigned char *p;
 
    /* Compute number of bytes mod 64 */
    count = (ctx.bits[0] >> 3) & 0x3F;
 
    /* Set the first char of padding to 0x80.  This is safe since there is
       always at least one byte free */
    p = ctx.in + count;
    *p++ = 0x80;
 
    /* Bytes of padding needed to make 64 bytes */
    count = 64 - 1 - count;
 
    /* Pad out to 56 mod 64 */
    if (count < 8) {
    /* Two lots of padding:  Pad the first block to 64 bytes */
    memset(p, 0, count);
    cMD5::byteReverse(ctx.in, 16);
    MD5Transform(ctx.buf, (unsigned long *) ctx.in);
 
    /* Now fill the next block with 56 bytes */
    memset(ctx.in, 0, 56);
    } else {
    /* Pad block to 56 bytes */
    memset(p, 0, count - 8);
    }
    cMD5::byteReverse(ctx.in, 14);
 
    /* Append length in bits and transform */
    ((unsigned long *) ctx.in)[14] = ctx.bits[0];
    ((unsigned long *) ctx.in)[15] = ctx.bits[1];
 
    MD5Transform(ctx.buf, (unsigned long *) ctx.in);
    cMD5::byteReverse((unsigned char *) ctx.buf, 4);
    memcpy(digest, ctx.buf, 16);
    memset(&ctx, 0, sizeof(MD5Context));        /* In case it's sensitive */
}
 

/* The four core functions - F1 is optimized somewhat */
 
/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))
 
/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f, w, x, y, z, data, s) \
    ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )
 
/*
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
void cMD5::MD5Transform(unsigned long buf[4], unsigned long in[16])
{
    register unsigned long a, b, c, d;
 
    a = buf[0];
    b = buf[1];
    c = buf[2];
    d = buf[3];
 
    MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
    MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
    MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
    MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
    MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
    MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
    MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
    MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
    MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
    MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
    MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
    MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
    MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
    MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
    MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
    MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
 
    MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
    MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
    MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
    MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
    MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
    MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
    MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
    MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
    MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
    MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
    MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
    MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
    MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
    MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
    MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
    MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
 
    MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
    MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
    MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
    MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
    MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
    MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
    MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
    MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
    MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
    MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
    MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
    MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
    MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
    MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
    MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
    MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
 
    MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
    MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
    MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
    MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
    MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
    MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
    MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
    MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
    MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
    MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
    MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
    MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
    MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
    MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
    MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
    MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
 
    buf[0] += a;
    buf[1] += b;
    buf[2] += c;
    buf[3] += d;
}
 
#ifdef sgi
#define HIGHFIRST
#endif
 
#ifdef sun
#define HIGHFIRST
#endif
 

#ifndef HIGHFIRST
    void cMD5::byteReverse(unsigned char *buf, unsigned longs)  
    {
        // Nothing
    }
#else
    // Note: this code is harmless on little-endian machines.
    void cMD5::byteReverse(unsigned char *buf, unsigned longs)
    {
        unsigned long t;
        do {
        t = (unsigned long) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
            ((unsigned) buf[1] << 8 | buf[0]);
        *(unsigned long *) buf = t;
        buf += 4;
        } while (--longs);
    }
#endif

Re: A better solution : here is the code

HughJampton

6:11 25 Apr '05

Excellent, very usefull class. One small syntax error prevents compiling: #define MD5STEP(f, w, x, y, z, data, s) \ ( w += f(x, y, z) + data, w = w<<s \| w>>(32-s), w += x ) Lose the backslash! Hugh
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Re: A better solution : here is the code

Anonymous

12:32 25 Apr '05

Hello This is no syntax error ! It is allowed to span #define's over multiple lines if every line ends with a backslash. On all modern compilers it should be possible to compile this. It seems you use an outdated compiler or a compiler that does not comply the standard rules for C++ syntax ! Try it on Visual Studio 6 and you will see no error ! Elmü
Sign In·View Thread·Permalink	2.00/5 (1 vote)

Re: A better solution : here is the code

HughJampton

15:00 25 Apr '05

Sorry, you're absolutley right. I am using VS6, but I'd un-split the line and left the '\' in. Hugh (who learns something new everyday!)
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Excellent code - one simple modification

Douglas R. Keesler

15:41 5 Jun '05

The MD5FinalToString() method returns an upper case hash, which is great for hashing files. You don't want to mess around with case matching to find out if the file was modified. However, if you're getting a hash from string input, most likely you are either creating an encryption key or storing a password validation string. In the latter event string case doesn't matter, but if you're creating an encryption key, mixed case makes a much stronger key. So I added a new function called MD5ToEncryptionKey(). It is basically a copy/paste of the aforementioned method, with a slight modification. Here is the code:

char* DCipher::MD5ToEncryptionKey()     //commented lines are my modifications
{
    unsigned char signature[16];
    MD5Final(signature);
 
	srand(16);      // Seed the Random Number Generator
	int val;        // Declare an integer

    ms8_MD5[0] = 0;
    char s8_Temp[5];
    for (int i=0; i<16; i++) 
    {
		val = rand() % 2;   // val = remainder of rand()/2
                           
		if(val < 1) // if even num, use upper - else use lower
			sprintf(s8_Temp, "%02X", signature[i]);
		else	
			sprintf(s8_Temp, "%02x", signature[i]);	
                             
        strcat(ms8_MD5, s8_Temp);
    }
 
    return ms8_MD5;
}

I simply seeded the random number generator to ensure the same random numbers would be generated on each call. Then by taking the modulus (remainder) of the random number divided by two, I determined whether it was odd or even. If an even random number use upper case hex, else use lower case hex (of course it has no effect on decimal digits).

Then I changed CalcMD5FromString() to return a call to this function.

One suggestion: if you use this for file encryption, change to function to accept an integer as a parameter and pass the file-size to the function, then you could seed the random number generator with that number. That way you would generate a different sequence of random numbers for each file, but ensure the sequence would repeat reliably for each file.

BTW, I incorporated this class into an overall file encryption class I was working on. The class is designed for internal file encryption. I use it in conjunction with my serialization overrides, to be able to read and save data with standard serialization methods, but always have the data encrypted on disk. The point of this class was to be able to generate encryption keys that were not generated of user input and were not stored anywhere. [It generates a 64-byte (512 bit) encryption key] I also wanted to be able to add a signature to the file that is not part of the encryption scheme, but would not allow files to be decrypted unless the signature matched - this is not for security, but for file control - so we don't try to decrypt files that don't belong to the app.

All of this has been incorporated into a single class which is achieved by creating an instance of the class, and then calling the method passing only the filepath and your apps signature. It's availabe in both generic class and DLL. I plan on posting an article on CP when I get time, offering this back to the public domain. It may be a couple weeks or so before I get time to write the article. If you want this, or need it sooner, post a message and I'll try to make a "article-less" download available.

It has some MFC in it, but very little. It could easily be modified for cross-platform projects.

Cheers to all!

In business, if two people always agree, one of them is unnecessary.

Re: A better solution : here is the code

pscholl

6:01 6 Jun '08

This is an excellent piece of code, but it has a problem with VS2008 Beta.
With a Unicode build, the following line

HANDLE h_File = CreateFile(s8_Path, GENERIC_READ, FILE_SHARE_READ, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

gives me the following error:
error C2664: 'CreateFileW' : cannot convert parameter 1 from 'const char *' to 'LPCWSTR'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

What is the correct syntax to avoid this error? I don't feel confident to experiment myself.

Likewise, with a non-unicode build I get the following warnings:
warning C4996: 'sprintf': This function or variable may be unsafe. Consider using sprintf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
warning C4996: 'strcat': This function or variable may be unsafe. Consider using strcat_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.

I would prefer not to disable the warnings, so if someone could tell me how to code this correctly so that it works with all builds in both VC6 and VS2008 I would very much appreciate it.

Thanks

Re: A better solution : here is the code

Elmue

14:40 6 Jun '08

Hello

It is obvious that you are new to C++.

I did not write the code to be compiled under Unicode.
Replace

char* cMD5::CalcMD5FromFile(const char *s8_Path)
....
HANDLE h_File = CreateFile(s8_Path, GENERIC_READ,

with

char* cMD5::CalcMD5FromFile(const WCHAR *u16_Path)
....
HANDLE h_File = CreateFileW(u16_Path, GENERIC_READ,

ATTENTION:
Do NOT replace the other chars* in the code !!!
They hold the MD5 data.

You switch off the usless warning with

#pragma warning(disable: 4996)

You can REALLY ignore the warnings.
There is NO problem with using sprintf() if you do it the right way.
Mircrosoft only tells you, that these functions have the risk of a buffer overflow if the code is badly written. But a clean code will NEVER produce a buffer overflow.

Newer code will use strings instead, but I suppose that you will not change all the code, which works perfectly, because of a stupid warning?

Elmü

Problem with this constructor.

Mr.Prakash

16:28 20 Jan '04

Cmd5Capi::Cmd5Capi(CString & csBuffer)
{
Digest(csBuffer);
}

I feel this constructed is not a good way to do the operation,
The Digest method is allocating memeory using GetBuffer and aquiring handle for the context, how is error handled if either of them fail?

This one i am not sure but looks obvious correct me if i am wroung
The return value of Digest is CString, while the return value of the constructor is the object itself, so how am i going to get the return value from this constructor?
the value is simplely lost making this constructor of no effect.

regards.

Tech.Support : Mam, is your pc running under windows?
Customer : No actually its close to the main door.

Compile Error !

freedem

15:00 2 Dec '03

I compiled your source with VC 6.0 , but got 17 errors : .... error C2065: 'HCRYPTPROV' : undeclared identifier error C2065: 'hCryptProv' : undeclared identifier error C2065: 'HCRYPTHASH' : undeclared identifier ..... but it can be compiled in vc++ .net . Why ?
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Re: Compile Error !

Victor M. Valenzuela

21:28 2 Dec '03

This definitions are part of the cryptoapi. Try to upgrade de VC 6 with the last service pack.
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Re: Compile Error !

Mihai Moga

20:44 29 Mar '06

add the following lines to your source code: #include <wincrypt.h> #pragma comment(lib, "crypt32") #pragma comment(lib, "advapi32") The Visual C++ .NET includes those files and more.
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Re: Compile Error !

bahram_cho

20:42 6 Apr '07

Hello add #define _WIN32_WINNT 0x0400 before #include "Wincrypt.h" in "md5Capi.h" file
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compilation Errors

rohitgad

7:40 24 Sep '03

Well, I wouldn't comment anything on the article or style of coding. I'm new to Crypto API, so this gave me a headstart. However, there wa a major issue I had to sort out to weed out the "undeclared identifier" compile time error associated with wincrypt.h. I noticed that wincrypt.h has an #if(_WIN32_WINNT >= 0x0400) in the benginning and a corresponding #endif statement at the end. I was compiling on Windows 2000. So the undeclared identifier issue was sorted out by commenting these 2 lines! Whew!
- Rohit

Re: compilation Errors

Vinayak

9:54 16 Jun '04

Hi,

I was wondering whether your solution to comment out lines from wincrypt.h was warranted or not because I do not know why did Microsoft put the following:

#if(_WIN32_WINNT >= 0x0400)
...

in the first place; and I think its not an elegant idea to hack around with header files outside the source control of the company which owns them, even if it means to just copy a new and modified wincrypt.h to your own project.

Maybe the following could be a more "non-invasive" method. Place the following lines in md5Capi.h:

#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0400
#include // Cryptographic API Prototypes and Definitions
#endif

However, I once again caution everyone who wishes to use this workaround that there must be a reason why the condition #if(_WIN32_WINNT >= 0x0400) is there in the first place, maybe someone could point it out to us.

Thanks and Regards,
Vinayak

Re: compilation Errors

Scott B.

18:59 21 Mar '06

The problem related to _WIN32_WINNT is explained in Microsoft article ID #320479 which includes an "official" workaround.
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Different Output

Atif Goheer

16:42 5 Aug '03

I am using the MD5 hash in my application. It works fine under normal settings but when i compile the project as UNICODE it starts giving me some crappy output. Any Answers??
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Re: Different Output

qihongbo

22:04 28 Sep '03

replace the code: BYTE* pbContent= (BYTE)csBuffer.GetBuffer(cbContent); to: USES_CONVERSION; BYTE pbContent= (BYTE*)T2A(csBuffer.GetBuffer(cbContent));
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Thanks

Paul Hooper

14:40 25 Apr '03

I actually haven't used your code but you have pointed me to something I didn't know existed. Great help. Paul Hooper If you spend your whole life looking over your shoulder, they will get you from the front instead.
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Crypto.h

Anonymous

3:15 4 Nov '02

where is the crypto.h file?
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Re: Crypto.h

Stefan-Mihai MOGA

0:49 27 Jun '05

The file you need is "wincrypt.h" which is located to PlatformSDK folder; this folder is part of Microsoft Visual C++ .NET package; if you are using Visual C++ 5.0/6.0 please install the Windows SDK package, available free of charge from Microsoft website. Good luck!
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Needs improvements

Vagif Abilov

2:46 30 Aug '02

There are several improvements that both article and code need:

1. More careful code packaging. It's not enough to ZIP all files in the directory. You end up with some temporary files included in the package. Remember that the more compact is solution, the more elegant it looks. In your package there are about 200 KB of files included. However, 3 largest files (with extension NCB, OPT and APS) are intermediate files that occupy about 150 KB (75%!) of space and are not part of the project. You should examine source files before including them into a package.

2. Better C++ coding. Let's take as an example the following method:

CString &Cmd5Capi::Digest(CString & csBuffer)

Why is buffer declared as "CString&" and "const CString&" (or even "LPCTSTR")? It should not be modified by the method. The same goes for return value. Why is it "CString&" and not "const CString&"?

3. The method digest might as well be declared as static, so MD5 digest could be computed without allocating an instance of Cmd5Capi class.

However, it's a good attempt for a first article.

Best regards

Vagif Abilov
MCP (Visual C++)
Oslo, Norway

If you're in a war, instead of throwing a hand grenade at the enemy, throw one of those small pumpkins. Maybe it'll make everyone think how stupid war is, and while they are thinking, you can throw a real grenade at them.
Jack Handey, Deep Thoughts