Active Directory Certificate Services (AD CS) requires key recovery agent certificates, exchange (XCHG) certificates, and keys in order to support key archival. The functioning of key recovery agent certificates, XCHG certificates, and the cryptographic service providers (CSPs) needed to create them is critical to a public key infrastructure.
Use a version of Windows Server 2008 that supports AD CS key archival
Key archival is available only with certification authorities (CAs) that are installed on computers running the Windows Server 2008 Enterprise operating system or the Windows Server 2008 Datacenter operating system.
Confirm that the CA you are using is installed on a computer running Windows Server 2008 Enterprise or Windows Server 2008 Datacenter.
To identify the Windows edition:
Open an Explorer window, right-click Computer, and click Properties.
In the section titled Windows edition, confirm that one of the versions that support key archival is listed.