Titel Deelnemers "Korte inhoud" "Towards a secure Kerberos key exchange with smart cards" "Nikos Mavrogiannopoulos, Andreas Pashalidis, Bart Preneel" "Public key Kerberos (PKINIT) is a standard authentication and key establishment protocol. Unfortunately, it suffers from a security flaw when combined with smart cards. In particular, temporary access to a user's card enables an adversary to impersonate that user for an indefinite period of time, even after the adversary's access to the card is revoked. In this paper, we extend Shoup's key exchange security model to the smart card setting and examine PKINIT in this model. Using this formalization, we show that PKINIT is indeed flawed, propose a fix, and provide a proof that this fix leads to a secure protocol. © 2013 Springer-Verlag Berlin Heidelberg." "Simulated annealing attack on certain fingerprint authentication systems" "Andreas Pashalidis" "Privacy-Friendly Checking of Remote Token Blacklists" "Roel Peeters, Andreas Pashalidis" "Security Considerations on Extending PACE to a Biometric-Based Connection Establishment" "Roel Peeters, Andreas Pashalidis" "The regulations of the European Union (EU) Council in 2004 are the basis of the deployment of electronic passports within the EU. Since then EU member states adopt the format and the access protocols to further electronic machine readable travel documents (eMRTD) like national electronic ID cards and electronic residence permits, respectively. The security protocols to communicate with an eMRTD are based on the paradigm of strong cohesion and loose coupling, i.e., each step is designed to ensure only a particular security goal like authorisation to access a certain data group, authenticity and integrity of the data, originality of the chip, or the linkage between the eMRTD and its holder. However, recently a discussion evolved to integrate the linkage security goal within the connection establishment, which currently only aims at limiting basic access of authorised terminals to the eMRTD. For instance, the BioPACE protocol proposes to replace the knowledge-based shared 'secret' of PACE by a biometric-based one. The goal of the paper at hand is twofold: First, we evaluate the BioPACE protocol and propose improvements to enhance its features. Second, we analyse the expediency of integrating our BioPACE version 2 into the eMRTD domain. Our initial evaluation shows that our BioPACE version 2 is expedient if the EAC protocols and the corresponding PKI are abandoned." "For Human Eyes Only: Security and Usability Evaluation" "Andreas Pashalidis, Nikos Mavrogiannopoulos, Benat Bermejo Olaizola, Xavier Ferrer" "A cross-protocol attack on the TLS protocol" "Nikos Mavrogiannopoulos, Frederik Vercauteren, Vesselin Velichkov, Bart Preneel" "This paper describes a cross-protocol attack on all versions of TLS; it can be seen as an extension of the Wagner and Schneier attack on SSL 3.0. The attack presents valid explicit elliptic curve Diffie-Hellman parameters signed by a server to a client that incorrectly interprets these parameters as valid plain Diffie-Hellman parameters. Our attack enables an adversary to successfully impersonate a server to a random client after obtaining 240 signed elliptic curve keys from the original server. While attacking a specific client is improbable due to the high number of signed keys required during the lifetime of one TLS handshake, it is not completely unrealistic for a setting where the server has high computational power and the attacker contents itself with recovering one out of many session keys. We remark that popular open-source server implementations are not susceptible to this attack, since they typically do not support the explicit curve option. Finally we propose a fix that renders the protocol immune to this family of cross-protocol attacks. Copyright © 2012 ACM." "Security implications in Kerberos by the introduction of smart cards" "Nikos Mavrogiannopoulos, Andreas Pashalidis, Bart Preneel" "Public key Kerberos (PKINIT) is a standardized authenti-cation and key establishment protocol which is used by the Windows active directory subsystem. In this paper we show that card-based public key Kerberos is awed. In particular, access to a user's card enables an adversary to impersonate that user even after the adversary's access to the card is re-voked. The attack neither exploits physical properties of the card, nor extracts any of its secrets. We propose protocol fixes and discuss properties that authentication and/or key establishment protocols should provide in order to be better equipped against the threats that arise due to the usage of smart cards. Copyright 2012 ACM." "Evaluating Tag-Based Preference Obfuscation Systems" "Andreas Pashalidis, Bart Preneel" "A Taxonomy Of Self-Modifying Code For Obfuscation" "Nikos Mavrogiannopoulos, Nessim Kisserli, Bart Preneel" "Self-modifying code is frequently used as an additional layer of complexity when obfuscating code. Although it does not provide a provable level of obfuscation, it is generally assumed to make attacks more expensive. This paper attempts to quantify the cost of attacking self-modified code by defining a taxonomy for it and systematically categorising an adversary's capabilities. A number of published methods and techniques for self-modifying code are then classified according to both the taxonomy and the model." "Relations Among Privacy Notions" "Andreas Pashalidis"