Single sign on technology enables shared access to a protected service, such as an application, from a plurality of dynamically associated computing devices. After logging into the application from one of the computing device, a user may access the application from the other computing devices without re-authentication. A user may also log out from the application from any of the computing device. Unique machine identifications, such as device DNA, for identifying each of the computing devices are used in, for example, a method, apparatus (such as a login server) and computer program product. A single session may be shared across multiple computing devices. The same authentication token, such as a SAML token, may also be used for all of the computing devices having the same user session.