Creating the CSP DLL

A CSP DLL is created like any other DLL. This procedure is explained in the MSDN documentation.

For a CSP with hardware components, the DLL might involve writing a smart card device driver or the embedded code that runs on the card. For information on writing any needed device drivers, see the Microsoft Device Developer Kit (DDK).

Every custom CSP DLL must expose all of the CryptoSPI functions listed in Entry Points. If a CSP does not actually support a particular function, a call to that function must at least return the E_NOTIMPL error code. A CSP that does not perform all of the cryptographic processes can be created; for example, a CSP specializing in signature verification that does not support data encryption functions.

Custom CSPs may involve more than one DLL; however, this is discouraged because it can create run-time complications. For more information, see CPAcquireContext. Regardless of the number of DLLs used for a custom CSP, all of them must be signed by Microsoft to enable the CSP to be used with the released versions of Windows 2000, Windows NT, or Windows 95 and later.