Architectural Support for the Pocket Companion:
A Highly Personal Hand-held Computing Device

Arne Helme and Sape J. Mullender
Faculty of Computer Science / SPA
University of Twente, Netherlands

An exiting prospect for the next decade is the deployment of a new generation of hand-held computers that can be used to participate in an on-line information community. The combination of networking and mobility will engender new applications and services, and provides means for users to stay in touch while one the move and to receive notifications of important events. In addition, it also gives people a whole new way to interact with the infrastructure of large public institutions, such as airports, supermarkets, or even whole cities.

The Moby Dick1 project is targeted at developing and defining the architecture of a new generation of mobile hand-held computers called Pocket Companions. The Pocket Companion is a small portable computer and communications device that can replace cash, cheque book passport, keys, diary, phone, pager, maps and possibly briefcases as well. Since we expect Pocket Companions to store wealth of personal information, we regard them as highly personal computers.

The communication infrastructure for the Pocket Companion will be provided by the public networks, building owners, airlines, railways and others. One interesting research problem is finding simple and effective ways in which bandwidth allocation and charging for bandwidth can be done in internetworks of communication-service providers. Another issue is the problem of locating a mobile device in order to send a message to it. Keeping track of billions of mobile devices in an internet of thousands of organizations requires completely new solutions -- the present ones do not scale nearly enough.

When one carries a Pocket Companion into an railway station, we may expect two kinds of services offered through the building network. One, as discussed above, is that of providing a connection to the internetwork, allowing the Pocket Companion to communicate to the outside world. The other is a service specific to railway stations: offering information about the railway timetable, platform information, directions through the building and the possibility to buy a ticket.

These services, offered by organizations receiving visitors and customers, work by virtue of a mechanism that detects newly arrived Pocket Companions and establishes a connection to them over which services provided by the organization are announced. Detecting new arrivals is needed for locating devices and data-relay services in any case.

An interesting area of study is how information services should be offered on a Pocket Companion. Allowing the organization offering the service to run arbitrary programs on one's highly personal Pocket Companion constitutes a serious security risk -- programs could, for instance, masquerade as regular applications and steal information from the unwitting user, or they could try to take over the Pocket Companion and steal its secrets (such as encryption keys).

The security architecture of the Pocket Companion and the infrastructure in which it is used will have to be carefully designed, especially since Pocket Companions will also be used in financial transactions.

1. Moby Dick is a joint European project (Esprit Long Term Research 20422).