The GINA operates in the context of the Winlogon process and, as such, the GINA DLL is loaded very early in the boot process. The GINA DLL must follow rules so that the integrity of the system is maintained, particularly with respect to interaction with the user.
Note GINA DLLs are ignored in Windows Vista.
The most common use of the GINA is to communicate with an external device such as a smart-card reader. It is essential to set the start parameter for the device driver to system (Winnt.h: SERVICE_SYSTEM_START) to ensure that the driver is loaded by the time the GINA is invoked.
The purpose of a GINA DLL is to provide customizable user identification and authentication procedures. The default GINA does this by delegating SAS event monitoring to Winlogon, which receives and processes CTL+ALT+DEL secure attention sequences (SASs). A custom GINA is responsible for setting itself up to receive SAS events (other than the default CTRL+ALT+DEL SAS event) and notifying Winlogon when SAS events occur. Winlogon will evaluate its state to determine what is required to process the custom GINA's SAS. This processing usually includes calls to the GINA's SAS processing functions.
Which registry key value to alter to load and run a custom GINA DLL.
How to test a GINA DLL.