An authorization server receives a request for an access token, for accessing a protected resource, from a client application executing on a device, wherein the request includes a client identifier that uniquely identifies the client application and a device identifier that uniquely identifies the device. The authorization server performs authentication of the client identifier and the device identifier. The authorization server returns a valid access token to the client application, based on the authentication of the client identifier and the device identifier, to enable the client application access to the protected resource.