Contoh Program C: Mengimpor Kunci Teks Biasa

Banyak fungsi dalam SDK ini mengharuskan Anda mengidentifikasi kunci dengan menggunakan handel HCRYPTKEY. Jika kunci Anda terkandung dalam array byte, Anda dapat membuat handel dengan menggunakan fungsiCryptImportKey seperti yang ditunjukkan dalam contoh berikut.

Contoh ini menunjukkan tugas dan fungsi CryptoAPI berikut:

• Memperoleh handel ke penyedia layanan kriptografi dengan memanggil CryptAcquireContext.
• Mengimpor kunci teks biasa ke dalam kontainer kunci CSP dengan memanggil CryptImportKey.
• Mengekspor kunci dari kontainer kunci dengan memanggil CyptExportKey.
• Mencetak kunci yang diekspor ke konsol untuk memverifikasi bahwa kunci teks biasa memang diimpor ke dalam kontainer.
• Melepaskan memori yang dicadangkan untuk kunci teks biasa.
• Merilis CSP dengan memanggil CryptReleaseContext.

#include <stdio.h>
#include <tchar.h>
#include <windows.h>
#include <wincrypt.h>
#pragma comment(lib, "crypt32.lib")

// DesKeyBlob:      A plaintext key BLOB stored in a byte array. The 
//                  byte array  must have the following format:
//                      BLOBHEADER hdr;
//                      DWORD dwKeySize;
//                      BYTE rgbKeyData [];

BYTE DesKeyBlob[] = {
    0x08,0x02,0x00,0x00,0x01,0x66,0x00,0x00, // BLOB header 
    0x08,0x00,0x00,0x00,                     // key length, in bytes
    0xf1,0x0e,0x25,0x7c,0x6b,0xce,0x0d,0x34  // DES key with parity
    };

int _tmain()
{
//--------------------------------------------------------------------
// Declare variables.
//
// hProv:           Cryptographic service provider (CSP). This example
//                  uses the Microsoft Enhanced Cryptographic 
//                  Provider.
// hKey:            Key to be used. In this example, you import the 
//                  key as a PLAINTEXTKEYBLOB.
// dwBlobLen:       Length of the plaintext key.
// pbKeyBlob:       Pointer to the exported key.

HCRYPTPROV hProv  = NULL;
HCRYPTKEY hKey    = NULL;
DWORD dwBlobLen;
BYTE* pbKeyBlob;

//--------------------------------------------------------------------
// Acquire a handle to the CSP.

if(!CryptAcquireContext(
   &hProv,
   NULL,
   MS_ENHANCED_PROV,
   PROV_RSA_FULL,
   CRYPT_VERIFYCONTEXT))
   {
      // If the key container cannot be opened, try creating a new
      // container by specifying a container name and setting the 
      // CRYPT_NEWKEYSET flag.
      if(NTE_BAD_KEYSET == GetLastError())
      {
         if(!CryptAcquireContext(
            &hProv,
            L"mytestcontainer",
            MS_ENHANCED_PROV,
            PROV_RSA_FULL,
            CRYPT_NEWKEYSET | CRYPT_VERIFYCONTEXT))
            {
               printf("Error in AcquireContext 0x%08x \n",
                  GetLastError());
               return 1;
            }
      }
      else 
      {
         printf(" Error in AcquireContext 0x%08x \n",GetLastError());
         return 1;
      }
   }

   // Use the CryptImportKey function to import the PLAINTEXTKEYBLOB
   // BYTE array into the key container. The function returns a 
   // pointer to an HCRYPTKEY variable that contains the handle of
   // the imported key.

   if (!CryptImportKey(
       hProv,
       DesKeyBlob,
       sizeof(DesKeyBlob),
       0,
       CRYPT_EXPORTABLE,
       &hKey ) )
   {
      printf("Error 0x%08x in importing the Des key \n",
         GetLastError());
   }

   // For the purpose of this example, you can export the key and 
   // print it to verify that the plain text key created above is  
   // the key that was imported into the CSP.
   // Call CryptExportKey once to determine the length of the key.
   // Allocate memory for the BLOB, and call CryptExportKey again
   // to retrieve the key from the CSP key container.

   if(!CryptExportKey(   
      hKey,    
      NULL,    
      PLAINTEXTKEYBLOB,
      0,    
      NULL, 
      &dwBlobLen)) 
      {
         printf("Error 0x%08x computing BLOB length.\n",
            GetLastError());
         return 1;
      }

   if(pbKeyBlob = (BYTE*)malloc(dwBlobLen)) 
   {
      printf("Memory has been allocated for the BLOB. \n");
   }
   else
   {
      printf("Out of memory. \n");
      return 1;
   }

   if(!CryptExportKey(   
      hKey, 
      NULL,    
      PLAINTEXTKEYBLOB,    
      0,    
      pbKeyBlob,    
      &dwBlobLen))
      {
         printf("Error 0x%08x exporting key.\n", GetLastError());
         return 1;
      }

   DWORD count = 0;
   printf("Printing Key BLOB for verification \n");
   for(count=0; count < dwBlobLen;)
   {
      printf("%02x",pbKeyBlob[count]);
      count ++;
   }

   // Free resources.

   if(pbKeyBlob)
   {
      free(pbKeyBlob);
   }

   if(hProv)
   {
      CryptReleaseContext(hProv, 0);
   }

    return 0;
}