how to pass the string to this MD5 program.? - c

Question

am trying to implement an application that uses an MD5 hash underneath, i have acquired the MD5 hash program from the internet, but i don't know how to pass the string from my program ( my program written in C) to the program that calculate the MD5 hash.
this is the main of the program that calculate the MD5 hash..
//
// MD5 Hashing Example - Using Windows Crypto API
//
// by Napalm # NetCore2K
//
#include <stdio.h>
#include <string.h>
#include "winmd5.h"
HCRYPTPROV hCryptProv;
int main(int argc, char *argv[])
{
int i;
CryptStartup();
if(argc > 1){
MD5Context ctx;
MD5Init(&ctx);
MD5Update(&ctx, (unsigned char *)argv[1], strlen(argv[1]));
MD5Final(&ctx);
for(i = 0; i < 16; i++)
printf("%02x", ctx.digest[i]);
printf("\n");
}else
printf("Usage: %s <string>\n", argv[0]);
CryptCleanup();
return 0;
}
this is the header file content..
//
// MD5 Hashing Example - Using Windows Crypto API
//
// by Napalm # NetCore2K
//
#include <windows.h>
#include <wincrypt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern HCRYPTPROV hCryptProv;
void PrintMD5(const char *);
typedef struct {
unsigned char digest[16];
unsigned long hHash;
} MD5Context;
BOOL CryptStartup()
{
if(CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET) == 0){
if(GetLastError() == NTE_EXISTS){
if(CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, 0) == 0){
return FALSE;
}
}
else return FALSE;
}
return TRUE;
}
void CryptCleanup()
{
if(hCryptProv) CryptReleaseContext(hCryptProv, 0);
hCryptProv = NULL;
}
void inline MD5Init(MD5Context *ctx)
{
CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &ctx->hHash);
}
void inline MD5Update(MD5Context *ctx, unsigned char const *buf, unsigned len)
{
CryptHashData(ctx->hHash, buf, len, 0);
}
void inline MD5Final(MD5Context *ctx)
{
DWORD dwCount = 16;
CryptGetHashParam(ctx->hHash, HP_HASHVAL, ctx->digest, &dwCount, 0);
if(ctx->hHash) CryptDestroyHash(ctx->hHash);
ctx->hHash = 0;
}
void PrintMD5(const char *s)
{
MD5Context ctx;
MD5Init(&ctx);
MD5Update(&ctx, (const unsigned char *)s, strlen(s));
MD5Final(&ctx);
int i;
for (i = 0; i < 16; i++) {
printf("%02x", ctx.hHash[i]);
}
printf("\n");
}
how should i call this Main(), and how to pass the String to it and get the result.?
thanks in advance.
Regards

Answer 1

You don't call main() again. You rather use this program as an example to write a separate function, like this:
void PrintMD5(const char *s)
{
MD5Context ctx;
MD5Init(&ctx);
MD5Update(&ctx, (const unsigned char *)s, strlen(s));
MD5Final(&ctx);
int i;
for (i = 0; i < 16; i++) {
printf("%02x", ctx.digest[i]);
}
printf("\n");
}
Then you can call this from your own program like:
PrintMD5("FooBarHelloWorld42");