//ver- und wieder entschlüsseln eines Strings mit einem Passwort
#include <windows.h>
#include <stdio.h>
#include <wincrypt.h>
 
// lc cryptencryptdata.c advapi32.lib
//----------------------------------------------------------------------------
void CryptandEncryptData(BYTE Buf[100],char *Password)
 {
  HCRYPTPROV hProv;
  HCRYPTHASH hPwdHash;
  HCRYPTKEY hKey;
  DWORD DataLen;
  DWORD i;
 
  DataLen = lstrlen(Buf)+1;
 
  printf("vorher:\t\t%s\n",Buf);
 if(!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0))
  {
    printf("error: %d\n",GetLastError());
    exit(1);
  }
 if(!CryptCreateHash(hProv, CALG_MD5, 0, 0, &hPwdHash))
  {
    printf("error: %d\n",GetLastError());
    CryptReleaseContext(hProv, 0);
    exit(1);
  }
 if(!CryptHashData(hPwdHash, Password, lstrlen(Password)+1, 0))
  {
    printf("error: %d\n",GetLastError());
    CryptDestroyHash(hPwdHash);
    CryptReleaseContext(hProv, 0);
    exit(1);
  }
 if(!CryptDeriveKey(hProv, CALG_RC4, hPwdHash, CRYPT_CREATE_SALT, &hKey)) 
  {
    printf("error: %d\n",GetLastError());
    CryptDestroyHash(hPwdHash);
    CryptReleaseContext(hProv, 0);
    exit(1);
  }
 
 printf("CryptDeriveKey:\t");
 for(i=0; i<DataLen; i++) printf("%02x ", Buf[i]);
 printf("\n");
 
 CryptEncrypt(hKey, 0, TRUE, 0, Buf, &DataLen, 100);
 
 printf("Crypt:\t");
 for(i=0; i<DataLen; i++) printf("0x%02x, ",Buf[i]);
 printf("\n");
 CryptDecrypt(hKey, 0, TRUE, 0, Buf, &DataLen);
 
 printf("Decrypt:\t");
 for(i=0; i<DataLen; i++) printf("%02x ",Buf[i]);
 printf("\n");
 printf("nachher:\t%s\n", Buf);
 
 CryptDestroyKey(hKey);
 CryptDestroyHash(hPwdHash);
 CryptReleaseContext(hProv, 0);
}
 
//--------------------------------------------------------------------------
 
int main (int argc, char **argv)
{
  /* Sind die erforderlichen Kommandozeilenargumente vorhanden? */
    if (argc != 3) {
        fprintf( stderr, "usage: %s stringtoCrypt password\n",argv[0]);
        exit(1);
    }
 
  //printf("%s\t%s\n", argv[1],argv[2]);
 CryptandEncryptData(argv[1],argv[2]);
 return 0;
}