Graphical identification and authentication

The graphical identification and authentication (GINA) is a component of Windows 2000, Windows XP and Windows Server 2003 that provides secure authentication and interactive logon services. GINA is a replaceable dynamically linked library that is loaded early in the boot process in the context of Winlogon when the machine is started. It is responsible for handling the secure attention sequence, typically Control-Alt-Delete, and interacting with the user when this sequence is received. GINA is also responsible for starting initial processes for a user (such as the Windows Shell) when they first log on. GINA is discontinued in Windows Vista.

A default GINA library, MSGINA.DLL, is provided by Microsoft as part of the operating system, and offers the following features:

Winlogon can be configured to use a different GINA, providing for non-standard authentication methods such as smart card readers or identification based on biometrics, or to provide an alternate visual interface to the default GINA. Developers who implement a replacement GINA are required to provide implementations for a set of API calls which cover functionality such as displaying a "workstation locked" dialog, processing the secure attention sequence in various user states, responding to queries as to whether or not locking the workstation is an allowed action, supporting the collection of user credentials on Terminal Services-based connections, and interacting with a screensaver.

A custom GINA could be made entirely from scratch, or just be the original GINA with modifications. A custom GINA can be specified by placing a string named GinaDLL in the registry location HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon. The Winlogon component is solely responsible for calling these APIs in the GINA library.

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