One aspect of the invention defines a process which allows application providers to remotely activate and authenticate logins from an application client. In one implementation, this is achieved through a three step approach. First, the application client notifies the application service of its successful installation (e.g. by accessing a unique URL). Second, it leverages the built-in security features of a mobile network (e.g. security mechanisms of GSM or IMS access security) to securely deliver a message containing authentication information to the application client. Examples of message transports are SMS or SIP with IPsec as specified by IMS. Third, this information is used to authenticate the application client when accessing the remote application service (e.g. via the Internet).