Download An Authentication Framework for Nomadic Users in Ubiquitous

47
3. If screen saver is active, it is unlocked.
4. Server sends a new session command to GNOME display manager (GDM) through a Client running in user space. As response, GDM starts a new session by launching an X server. The authentication Server waits for a predefined period of time to allow new session to start. It expects a feedback from the authentication Client running within new session. However, if it does not receive any reply, the new session is killed to avoid any security breach.
5. It switches the computer display to currently active virtual terminal, so that user can view his session.
6. It also locks or suspends all those sessions which do not belong to the current user.
3. State=Known: This state is reached whenever RFID reader reports the tag whose corresponding user is already authenticated. It means that same user is present across multiple authentication events, so it is a kind of steady state. In our prototype, the repeated authentication is necessary to achieve persistence. In this state, following functions are performed.
1. It keeps the session unlocked.
2. It switches the display to the virtual console terminal corresponding to the currently active user.
The authentication Server communicates using network sockets, with other modules of the authentication mechanism. The numerical values of sockets can be found in the header file. Here, we describe them by referring to their enumerated names. Following sockets are used for the interprocess communication.
�
SESSION_FEEDBACK_SOCKET: This socket is used to receive messages from all Clients.
�
USER_BROADCAST_SOCKET: It is used to broadcast user name in the system. Since, there are multiple Client applications in the system, therefore each Client is associated with a unique socket number in a set. This socket serves as base number for the set. For example the authentication Client corresponding to the first active session is USER_BROADCAST_SOCKET + 1, the second session Client is USER_BROADCAST_SOCKET + 2 and so on. �
USER_CMD_SOCKET: From this socket, Server receives commands from user programs. These commands are in a standard format. For example, DLG application sends delegation or revocation requests on this socket. �
USER_REPLY_SOCKET: This socket complements USER_CMD_SOCKET, and thus it is used to send replies to corresponding user program for their requests.
5. Authentication 'Client'
The authentication Client is a process which runs in user space with the corresponding user's privileges. This means, on a given system, there are multiple copies of Client application corresponding to each user. Server keeps track of all Clients running in a particular session and only sends the session specific commands. Client serves two purposes.
1. It receives commands from Server and executes them in the current user space. However, it does not know which commands are being sent, as the authentication Client always receive a formatted string and execute it on console. In this sense, it may be considered as an access point for Server in a particular session.