authenticated-key-exchange.md

title	description	keywords	ms.date
Authenticated Key Exchange	Authenticated Key Exchange	authenticated key exchange WDK COPP key exchange WDK COPP	04/20/2017

Authenticated Key Exchange

This section applies only to Windows Server 2003 SP1 and later, and Windows XP SP2 and later.

The following figure shows establishing a secure connection through authentication and key exchange. First, the video miniport driver supplies the graphics hardware certificate to the application. Next, the application extracts the public key from the graphics hardware certificate. After the application generates a data integrity key (k_DI), the application uses the public key to encrypt a sequence that includes the data integrity key and supplies the sequence to the driver.

Command and status messages are subsequently passed unencrypted; however, for each message, MACs are created by using the data integrity key.

:::image type="content" source="images/coppkey.png" alt-text="Diagram illustrating the process of authentication and key exchange to establish a secure connection.":::

For more information about MACs, see Cryptographic Primitives Used by COPP.

The following table describes the values in the preceding figure.

Value	Description
rGH	128-bit random number generated by the driver.
CertGH	Variable-length digital certificate used by the graphics hardware.
PGH(rGH, kDI, status_start, command_start)	Start sequence for the secure channel, which consists of the following items concatenated together: 128-bit random number generated by the driver. 128-bit random data integrity session key generated by the application. 32-bit random starting status sequence number generated by the application. 32-bit random starting command sequence number generated by the application. The application encrypts the sequence by using the public key obtained from the graphic hardware certificate. The sequence is 2,048 bits long; the remainder of the sequence is padded with 0s.