EncryptionBlt routine

The EncryptionBlt function reads encrypted data from a protected surface.



__checkReturn HRESULT APIENTRY EncryptionBlt(
  _In_       HANDLE                  hDevice,
{ ... }


hDevice [in]

A handle to the display device (graphics context).

pData [in]

A pointer to a D3DDDIARG_ENCRYPTIONBLT structure that describes the parameters of the encrypted bit-block transfer (bitblt) operation.

Return value

EncryptionBlt returns one of the following values:

Return codeDescription

The encrypted bitblt operation is successfully performed.


EncryptionBlt could not allocate the required memory for it to complete.


The driver does not support the EncryptionBlt function.



Hardware and drivers can optionally support EncryptionBlt. Some hardware might also require to use a separate key to decrypt the data that is read back. The driver returns this key in a block of memory that the pIV member of D3DDDIARG_ENCRYPTIONBLT points to.

If the driver and hardware use a separate key for the encryption bitblt, the application must recognize this fact and use the key.

If the crypto type is D3DCRYPTOTYPE_AES128_CTR, pIV points to a D3DAES_CTR_IV structure that the application allocates. However, the actual contents of the D3DAES_CTR_IV structure are filled in by the driver and hardware. When the driver and hardware generate the first initialization vector, they should initialize the IV member of the D3DAES_CTR_IV structure to a random number (that is not too big). Each subsequent initialization vector should simply increment the IV member, which ensures that the IV always increases in value. This fact enables the application to validate that the same IV is never used multiple times with the same key pair.

EncryptionBlt cannot read back sub-rectangles. EncryptionBlt also cannot read back partially encrypted buffers because many of the hardware-based solutions do not allow non-encrypted reads from protected memory.

The Direct3D runtime verifies that the destination surface specified by the DstSubResourceIndex member of D3DDDIARG_ENCRYPTIONBLT is in system memory and that no stretching, colorspace conversion, and so on is performed. An application should ensure that the system memory buffer is properly aligned and that the buffer's size matches the source surface. The driver should verify the memory alignment and the buffer size (DstResourceSize member of D3DDDIARG_ENCRYPTIONBLT) and fail if these conditions are not correct.


Target platform


EncryptionBlt is supported beginning with the Windows 7 operating system.


D3dumddi.h (include D3dumddi.h)

See also




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