15. A computer readable memory comprising program instructions that, when executed by a processor, implement a method managing access to a plurality of applications using a central server, the method comprising: receiving a user name and a user password of a user from a first application; authenticating the user using the user name and password; generating, in response to the successful authentication, identity assertion information comprising information associated with the user for use by a plurality of applications to authenticate the user; generating a first artifact associated with the identity assertion information, wherein the first artifact is used to obtain the identity assertion information; sending the first artifact to the first application; receiving the first artifact and a request for the identity assertion information from a second application, wherein the second application receives the first artifact from the first application; verifying the validity of the first artifact upon receipt from the second application; retrieving, after successful validation of the first artifact, the identity assertion information for the user using the first artifact; sending the identity assertion information to the second application, wherein the second application uses the identity assertion information to authorize the user to access the second application; rendering the first artifact invalid for future use by any of the plurality of applications; receiving a request for a second artifact from the second application; and providing the second artifact associated with the identity assertion information, wherein the second artifact is used to obtain the identity assertion information, wherein the first application and the second application are members of the plurality of applications.
17. The computer readable memory of claim 15 , wherein the identity assertion information is stored in the central server.