ID3D11VideoContext::DecryptionBlt method (d3d11.h)

Article
07/27/2022

Writes encrypted data to a protected surface.

Syntax

void DecryptionBlt(
  [in] ID3D11CryptoSession        *pCryptoSession,
  [in] ID3D11Texture2D            *pSrcSurface,
  [in] ID3D11Texture2D            *pDstSurface,
  [in] D3D11_ENCRYPTED_BLOCK_INFO *pEncryptedBlockInfo,
  [in] UINT                       ContentKeySize,
  [in] const void                 *pContentKey,
  [in] UINT                       IVSize,
  [in] void                       *pIV
);

Parameters

[in] pCryptoSession

A pointer to the ID3D11CryptoSession interface.

[in] pSrcSurface

A pointer to the surface that contains the source data.

[in] pDstSurface

A pointer to the protected surface where the encrypted data is written.

[in] pEncryptedBlockInfo

A pointer to a D3D11_ENCRYPTED_BLOCK_INFO structure, or NULL.

If the driver supports partially encrypted buffers, pEncryptedBlockInfo indicates which portions of the buffer are encrypted. If the entire surface is encrypted, set this parameter to NULL.

To check whether the driver supports partially encrypted buffers, call ID3D11VideoDevice::GetContentProtectionCaps and check for the D3D11_CONTENT_PROTECTION_CAPS_PARTIAL_DECRYPTION capabilities flag. If the driver does not support partially encrypted buffers, set this parameter to NULL.

[in] ContentKeySize

The size of the encrypted content key, in bytes.

[in] pContentKey

A pointer to a buffer that contains a content encryption key, or NULL. To query whether the driver supports the use of content keys, call ID3D11VideoDevice::GetContentProtectionCaps and check for the D3D11_CONTENT_PROTECTION_CAPS_CONTENT_KEY capabilities flag.

If the driver supports content keys, use the content key to encrypt the surface. Encrypt the content key using the session key, and place the resulting cipher text in pContentKey. If the driver does not support content keys, use the session key to encrypt the surface and set pContentKey to NULL.

[in] IVSize

The size of the pIV buffer, in bytes.

[in] pIV

A pointer to a buffer that contains the initialization vector (IV).

For 128-bit AES-CTR encryption, pIV points to a D3D11_AES_CTR_IV structure. The caller allocates the structure and generates the IV. When you generate the first IV, initialize the structure to a random number. For each subsequent IV, simply increment the IV member of the structure, ensuring that the value always increases. This procedure enables the driver to validate that the same IV is never used more than once with the same key pair.

For other encryption types, a different structure might be used, or the encryption might not use an IV.

Return value

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

Not all hardware or drivers support this functionality for all cryptographic types. This function can only be called when the D3D11_CONTENT_PROTECTION_CAPS_DECRYPTION_BLT cap is reported.

This method does not support writing to sub-rectangles of the surface.

If the hardware and driver support a content key:

The data is encrypted by the caller using the content key.
The content key is encrypted by the caller using the session key.
The encrypted content key is passed to the driver.

Otherwise, the data is encrypted by the caller using the session key and NULL is passed as the content key.

If the driver and hardware support partially encrypted buffers, pEncryptedBlockInfo indicates which portions of the buffer are encrypted and which is not. If the entire buffer is encrypted, pEncryptedBlockinfo should be NULL.

The D3D11_ENCRYPTED_BLOCK_INFO allows the application to indicate which bytes in the buffer are encrypted. This is specified in bytes, so the application must ensure that the encrypted blocks match the GPU’s crypto block alignment.

This function does not honor a D3D11 predicate that may have been set.

If the application uses D3D11 queries, this function may not be accounted for with D3D11_QUERY_EVENT and D3D11_QUERY_TIMESTAMP when using feature levels lower than 11. D3D11_QUERY_PIPELINE_STATISTICS will not include this function for any feature level.

Requirements

Requirement	Value
Minimum supported client	Windows 8 [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2012 [desktop apps \| UWP apps]
Target Platform	Windows
Header	d3d11.h