Activity Report 2004

Laboratory of Cryptography and System Security (CrySyS)
Department of Telecommunications
Budapest University of Technology and Economics

The laboratory has three types of activities: research, teaching, and maintaining industrial partnership. Following this classification, this report is divided into three parts.

In 2004, we did research in three areas: security in the world of ubiquitous computing, security of smart card applications, and Internet security.

Security in the world of ubiquitous computing

The vision of ubiquitous computing is to surround people with all kinds of embedded computing devices that could assist them in their everyday activity and make their life easier. In order to take full advantage of this new paradigm, it is expected that these devices will form networks through which they can communicate with each other and reach existing computing infrastructures such as the Internet. In many applications, devices will use wireless links; however, they will be unable to transmit to a large distance due to severe constraints on their available energy and bandwidth. These issues have generated much interest in a new generation of networking technology called multi-hop wireless networking. Examples for multi-hop wireless networks include sensor networks, mesh networks, and mobile ad hoc networks.

Since multi-hop wireless networks are of paramount importance for ubiquitous computing, we have focused our research on them. In particular, we worked on the following two topics: routing security and cooperation.

AZIMUTH - analyzing and designing secure routing protocols for multi-hop wireless networks

Routing is one of the most basic networking functions in multi-hop networks. Hence, an adversary can easily paralyze the operation of the network by attacking the routing protocol. This has been realized by many researchers, and several "secure" routing protocols have been proposed for wireless ad hoc networks. However, the security of those protocols have been analyzed either by informal means only, or with formal methods that have never been intended for the analysis of this kind of protocols. Our research revealed that many of the proposed protocols (e.g., SRP and Ariadne) are flawed in the sense that they do not achieve the properties claimed by their authors. We beleive that the main reason for this is the lack of a mathematical model in which rigourous definitions of security can be given and protocols can be proven secure (or not) with respect to these definitions. We addressed these problems by proposing a sound mathematical technique for the analysis of routing protocols. Our method is an adoptation of the simulation paradigm to ad hoc routing protocols. We demonstrated the usefulness of our approach by proposing a new on-demand source routing protocol, called endairA, and proving it to be secure in our model.

Researchers involved in this project: Gergely Ács (student), Levente Buttyán, and István Vajda

Publications: BV04sasn, A04tdk

INCOME - incentives for cooperation in multi-domain wireless networks

In multi-hop wireless networks, data packets are relayed by the devices (and base stations) in several wireless hops from their source to their destination. Hence, the proper operation of the network requires the devices to cooperate. If the devices belong to the same administrative domain, then they collaborate by default. This is the common situation in military and rescue applications. However, in many civilian applications, the devices fall into different administrative domains. In this case, cooperation between devices of different domains cannot be taken for granted, because it costs energy and it has no direct advantages. In fact, the devices (or their users) may tend to be selfish, and deny packet forwarding for the benefit of devices belonging to foreign domains in order to save their own resources. In this project, our goal was to study under what conditions cooperation can emerge spontaneously in the network. The emergence of cooperation between agents of conflicting interests has been observed in some biological, political, and social systems. The question we were interested in is: can this happen in wireless networks too?

Note: Some parts of this project has been carried out in collaboration with the group of Prof. Jean-Pierre Hubaux at the Swiss Federal Institute of Technology -- Lasuanne (EPFL).

Researchers involved in this project: Levente Buttyán, Tamás Holczer (student), Péter Schaffer (student)

Publications: BHS04ht, HS04tdk, FHB05persens, FHB05ieeetmc

Security of smart card applications

A smart card is a small plastic card with an embedded microchip. Regarding its capabilities, a smart card is a micro-computer: it can store and process data. However, compared to a traditional computer, smart cards are very easy to carry around. Smart cards have many possible applications. Due to their tamper resistance and computing capabilities they are often used in security applications, such as electronic ID cards, digital signature cards, access control to buildings, logon to a computer, electronic purse, SIM cards (for cellphones), pre-paid telephone cards, public transport e-tickets, pay TV applications, ... All in all, smart cards are becoming very widespread.

SMARTER - smart card applications and their security

The goal of SMARTER is to study various problems related to the safe usage of smart cards in security applications. In particular, we have studied the untrusted terminal problem, which stems from the fact that smart cards have no user interface, and hence, they are unable to communicate with the user directly. Communication is only possible with the aid of a terminal, which leads to several security problems. For example, the terminal may perform a man-in-the middle attack. Although the problem is widespread, it has relatively little literature. We have developed a solution which can alleviate the problem. It is based on a new concept called conditional signatures. We have also implemented a prototype of our proposal on Axalto Java cards.

Researchers involved in this project: István Zsolt Berta, Levente Buttyán, István Vajda, and Tamás Veiland (student)

Publications: BBV04itcc, BBV04cardis, BB04niif, BV05tatra

Internet security

Internet security is a broad topic; we have focused our research on mechanisms to protect against malicious code, spam, and DoS attacks. Internet e-mail viruses are generating 40-60% of total Internet e-mail traffic. They infect millions of computers and by doing so they enable identity theft, spamming through victimís computer, etc. Anti-virus softwares have not solved the problem of internet viruses yet. In particular, they do not stop the rapid propagation of new viruses. A system approach seems to be necessary to achieve a better protection. Our goal is to design and analyse small, collaborative components that enable

Researchers involved in this project: Boldizsár Bencsáth, Gábor Szabó (student), Géza Szabó (student), and István Vajda

Publications: BV04cts, BV04softcom, B04niif, B04hisec

Publications in 2004

Journal and magazine papers:
[ZB04pp]  L. Zömbik and L. Buttyán,
Modelling Location Reveal Attacks in Mobile Systems,
Periodica Polytechnica, Vol. 48 No. 1-2, pp.85-100, 2004.

[BHC04jcs]  L. Buttyán, J.-P. Hubaux, and S. Capkun,
A Formal Model of Rational Exchange and its Application to the Analysis of Syverson's Protocol,
Journal of Computer Security, Vol. 12 No. 3-4, pp. 551-587, 2004.

[BHS04ht]  L. Buttyán, T. Holczer, and P. Schaffer
Incentives for Cooperation in Multi-hop Wireless Networks, (in Hungarian)
Hiradástechnika, March 2004.

Conference and workshop papers:
[BV04sasn]  L. Buttyán and I. Vajda,
Towards Provable Security for Ad Hoc Routing Protocols,
2nd ACM Workshop on Security in Ad Hoc and Sensor Networks (SASN 2004)
Washington DC, USA, October 25, 2004.

[FHB04wiopt]  M. Félegyházi, J.-P. Hubaux, and L. Buttyán,
Equilibrium Analysis of Packet Forwarding Strategies in Wireless Ad Hoc Networks -- the Dynamic Case, (2-page abstract)
2nd Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt 2004)
Cambridge, UK, March 24-26, 2004.

[BBV04cardis]  I. Berta, L. Buttyán, and I. Vajda
Privacy Protecting Protocols for Revokable Digital Signatures,
6th IFIP Conference on Smart Card Research and Advanced Application (CARDIS 2004)
Toulouse, France, August 23-26, 2004.

[BBV04itcc]  I. Berta, L. Buttyán, and I. Vajda
Mitigating the Untrusted Terminal Problem Using Conditional Signatures,
International IEEE Conference on Information Technology (ITCC 2004)
Las Vegas, NV, USA, April 5-7, 2004.

[BB04niif]  I. Zs. Berta and B. Bencsáth
Sending authentic messages from malicious terminals,
Networkshop 2004 Conference, NIIF, Hungary, 2004.

[BV04cts]  B. Bencsáth, I. Vajda,
Protection Against DDoS Attacks Based On Traffic Level Measurements,
International Symposium on Collaborative Technologies and Systems,
San Diego, CA, USA, January 2004.

[BV04softcom]  B. Bencsáth, I. Vajda,
Trap E-mail Address for Combating E-mail Viruses,
International conference on software, telecommunications and computer networks (SOFTCOM 2004),
University of Split, October, 2004.

[B04niif]  B. Bencsáth
The problems and connections of network virus protection and the protection against denial of service attacks,
Networkshop 2004 Conference, NIIF, Hungary, 2004.

[B04hisec]  B. Bencsáth,
System oriented protection against internet e-mail viruses,
HISEC 2004 Conference,
Budapest, 2004.

[A04tdk]  G. Ács
Provable security for ad hoc routing protocols, (in Hungarian)
Student Conference, November 2004.
II. prize

[HS04tdk]  T. Holczer and P. Schaffer
Spontaneous cooperation in multi-domain sensor networks, (in Hungarian)
Student Conference, November 2004.
III. prize

[D04tdk]  L. Dóra
Wormhole detection in sensor networks, (in Hungarian)
Student Conference, November 2004.
III. prize

Accepted papers (to be published in 2005):
[FHB05persens]  M. Félegyházi, J.-P. Hubaux, and L. Buttyán,
Cooperative Packet Forwarding in Multi-Domain Sensor Networks,
First International Workshop on Sensor Networks and Systems for Pervasive Computing (PerSeNS 2005)
Kauai Island, Hawaii, March 8, 2005.

[BBHJ05ieeetmc]  N. Ben Salem, L. Buttyán, J.-P. Hubaux, and M. Jakobsson
Node Cooperation in Hybrid Ad hoc Networks,
to appear in IEEE Transactions on Mobile Computing.

[FHB05ieeetmc]  M. Félegyházi, J.-P. Hubaux, and L. Buttyán,
Nash Equilibria of Packet Forwarding Strategies in Wireless Ad Hoc Networks,
to appear in IEEE Transactions on Mobile Computing.

[CHB05ieeetmc]  S. Capkun, J.-P. Hubaux, and L. Buttyán,
Mobility Helps Peer-to-Peer Security,
to appear in IEEE Transactions on Mobile Computing.

[BV05tatra]  I. Zs. Berta and I. Vajda,
Limitations of humans when using malicious terminals,
to appear in Tatra Mountains Mathematical Publications.

[BBV05ITsec]  I. Berta, L. Buttyán, and I. Vajda,
Standards for Product Security Assessment,
to appear in H. Bidgoli, editor-in-chief, The Handbook of Information Security, John Wiley & Sons, Inc.


Our teaching activities are mainly related to the base course called Information Security and to the Special on Security of Information and Communication Systems. In 2004, we worked out 1 course (Foundations of Secure Electronic Commerce) and three laboratory exercises (Smart Cards I, Smart Cards II, and PKI and SSL). This completes our contribution (2 courses and 5 laboratory exercises) to the special.

Courses given in 2004

Boldizsár Bencsáth and István Zsolt Berta provided help in the correction of the tests and exams during the whole year.

Laboratory exercises in 2004

The exercises were developed by István Zsolt Berta and Attila Bognár with the help of Boldizsár Bencsáth. The exercise sessions were supervised by Boldizsár Bencsáth, István Zsolt Berta, and László Bokor.

Student semester projects in 2004

Projects supervised by Levente Buttyán:

Projects supervised by Boldizsár Bencsáth:

Diploma projects in 2004

Industrial connections

In 2004, we significantly increased the number of our industrial connections via the establishment of long-term relationships with major smart card manufacturers, participation in an R&D; project, and consulting.

Miscellaneous notes

Attila Bognár left the lab in the summer of 2004. István Zsolt Berta left the lab in December 2004.

buttyan (at)