e) Keystroke Analysis

A patent about a biometric system performing keystroke analysis has been obtained in 2002. The method developed showed to be by far the best one (among those performing keystroke analysis) able to recognize legal users and impostors who try to access a controlled resource. In 2002 the method has been extended to the analysis of free text and thoroughly tested. It has been showed to be the only method found in the literature to be able to effectively discriminate between legal users and intruders of the monitored system, with a very high level of accuracy and transparently to the users (and impostors).

The X.500 protocol directory allows to realize a sophisticated distributed database with a partial reproduction of the database. Substantially, it is a free scheme with research functions for the database content. In the 1992 standard from ISO and CCITT, the functionality of the X.500 service was extended introducing access control. Basic Access Control functionalities have been studied, and an algorithm was developed to verify at runtime the access control for a generic X.500 database. A new interesting concept has originated from the research and development on Directories: The Concept of MetaDirectory. A MetaDirectory is a controlled union of all the Directories of an Organisation, that on one side allows to have a single point of access to a common repository of data for the whole organisation, and on the other side allows to synchronise and the data contained in different data bases and to control the flow of data from one data base to another that is configured to receive the updates of the data from the "master" one. The interesting point is that the master ship is defined at the attribute level, and the values of attributes can be obtained via an appropriate computation from one or moresource attributes. We are experimenting with these new concepts in the area of controlled access to University data from web servers.

With the development of applications on computer networks, the problem of managing complex network systems became more and more important. Both within ISO/ITU and Internet, specific protocols and informative models have been developed to realize a distributed system to handle both network elements and distributed network applications. The two network management models are not equivalent, even if a comparative study of them points out interesting analogies. Cryptographic key management in a security system for telecommunications is an interesting area to apply the management model and the corresponding OSI protocols.

An interesting problem the is now being studied is the monitoring of Service Level Agreements. With the widespread adoption of outsourcing contract for the ITC services, the need has emerged of defining precisely the LEvel of Service that the provider must offer to the Users. The finalisation of document called Service Level Agreement is considered to be extremely beneficial to the achievement of customer satisfaction. The problem is now that of being able to monitor level of service that is being offered to group of Users and to be able to manage the resources of the ITC system so that the level of service defined in the SLA is actually met, thus avoiding that the users perceive a degradation of service.

MOnitoring Service LEvel Agreements is radically different than monitoring the performance of devices, computers, or telecommunication lines, because requires the measure of the service that is being delivered the actual users by applications, and not the service that the application "believes" is delivering to users. A Service Level Agreement Monitoring system must be able to allow the operators to identify the real causes of performance degradation, before the users perceive such a degradation and complain with the administrators.

This research is concerned with public key certification in distributed environments, proposing a certification scheme to exchange documents that are digitally signed. Our system, proposed in collaboration with the University of Cambridge, includes the implementation of a separate authority dedicated to delete the public key certificates that are no longer valid. Log file records are bound in a chain of hash values, so that they may not be deleted by the authority in an undetected way. The system has been implemented and a series of experiments is starting to integrate the above certification system with a few browser and mail services available on the market, both in Unix and Windows NT environments. Through this structure is possible to obtain a number of secure services that require signed and/or encrypted documents to be sent.

h.1) Secure Mailtools

In this research we studied PGP (Pretty Good Privacy), the most popular mail encryption and signature tool available worldwide. Within the context of two undergraduate theses, that were supervised by the security group, a public domain program, named "ACT", was implemented in 1997 and maintained in 1998, 1999, 2000, 2001 and 2002. This tool is compatible with PGP (versions prior to 5.0), but solves some of its weaknesses.

h.2) Digital Signatures and Authentication

The research was about the study of the mechanism to generate digital signatures based on public key algorithms. In collaboration with the University of Cambridge we made a new and alternative proposal to generate digital signatures based only on hash function chains. This mechanism turns out to be more efficient than the traditional approaches, and moreover it does not involve all the problems connected to the restrictions imposed by some countries about the export of encryption software.