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Create Content Key Example

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[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The content key is used to encrypt media samples for Windows Media DRM Import. The following code example demonstrates how to create and initialize a content key structure.

HRESULT CreateContentKey( WMDRM_IMPORT_CONTENT_KEY **ppContentKey, DWORD *pcbContentKey)
{
    // TODO: Set this value to the desired number of bytes for the content key data. 
    const DWORD IV_DATA_SIZE = 16;
    HRESULT hr = S_OK;
    WMDRM_IMPORT_CONTENT_KEY *pContentKey = NULL;

    // The content key.
    const BYTE rgbContentKey[] = {
        0x67, 0x39, 0x83, 0xb9,
        0x52, 0xa8, 0xe3
    };        
    const DWORD CONTENT_KEY_DATA_SIZE = sizeof(rgbContentKey);

    // Compute the total size of the content key structure
    DWORD cbContentKey = sizeof( WMDRM_IMPORT_CONTENT_KEY ) +
      IV_DATA_SIZE + CONTENT_KEY_DATA_SIZE;

    // Make sure we have a valid 
    if( NULL == ppContentKey )
    {
        hr = E_POINTER;
        goto EXIT;
    }

    // Allocate the content key, locally first
    pContentKey = (WMDRM_IMPORT_CONTENT_KEY *)new BYTE[ cbContentKey ];
    
    // Check the allocation was successful 
    if( NULL == pContentKey )
    {
        hr = E_OUTOFMEMORY;
        goto EXIT;
    }

    // Ininitalize the key
    ZeroMemory( pContentKey, cbContentKey );
    pContentKey->dwVersion = 0;
    pContentKey->cbStructSize = cbContentKey;

    // Set the initialization vector key type 
    pContentKey->dwIVKeyType = WMDRM_KEYTYPE_RC4;
    pContentKey->cbIVKey = IV_DATA_SIZE;
    
    // Generate a random initialization vector. Note that this random number
    //  generator is not very good. It is only intended to be demonstrative
    //  and it is not recommended for use in commercial strength code.
    srand((unsigned int)time(NULL));
    BYTE* pKeyData = pContentKey->rgbKeyData;
    for (size_t i = 0; i < IV_DATA_SIZE; ++i)
    {
        *pKeyData++ = (BYTE)(rand() & 0xFF); 
    }   
    
    // Set the content key type.
    pContentKey->dwContentKeyType = WMDRM_KEYTYPE_COCKTAIL;
    pContentKey->cbContentKey = CONTENT_KEY_DATA_SIZE;

    // Fill out the content key. 
    for (size_t i = 0; i < CONTENT_KEY_DATA_SIZE; ++i)
    {
        *pKeyData++ = rgbContentKey[i]; 
    }   
    

    // If all has been successful, set the parameters
    *ppContentKey = pContentKey;
    pContentKey = NULL;
    *pcbContentKey = cbContentKey;

EXIT:
    SAFE_ARRAY_DELETE( pContentKey );
    return hr;
}

DRM Import Examples