APPLICATION USER SINGLE SIGN-ON

Systems and methods are disclosed for accessing protected data. A computing device may have a secured stared storage accessible by two or more applications operating on the mobile device. The computing device may obtain a first token from an authorization service to verify user identity for a first application. The first token may be stored in the shared storage area, and be accessible to one or more applications sharing the storage space. In response to a user attempt to access a web service using a second application, the user identity may be verified using the first token. The authorization service may verify user credentials, and send a second token to the computing device. The second token may be a proxy ticket authorizing access and exchange of protected data between the second application and a web service. The second token may also be stored in the secure storage area.