Karim El Defrawy

Attacks on physical-layer identification

Physical-layer identification of wireless devices, commonly referred to as Radio Frequency (RF) fingerprinting, is the process of identifying a device based on transmission imperfections exhibited by its radio transceiver. It can be used to improve access control in wireless networks, revent device cloning and complement message authentication protocols. This paper studies the feasibility of performing impersonation attacks on the modulation-based and transient-based fingerprinting techniques. Both techniques are vulnerable to impersonation attacks; however, transient-based techniques are more difficult to reproduce due to the effects of the wireless channel and antenna in their recording process. We assess the feasibility of performing impersonation attacks by extensive measurements as well as simulations using collected data from wireless devices. We discuss the implications of our findings and how they affect current device identification techniques and related applications.

Leveraging Social Contacts for Message Confidentiality in Delay Tolerant Networks

Delay- and disruption-tolerant networks (DTNs) can bring much-needed connectivity to rural areas and other settings with limited or non-existing infrastructures. High node mobility and infrequent connectivity inherent to DTNs make it challenging to implement simple and traditional security services, e.g., message integrity and confidentiality.In this paper, we focus on the problem of initial secure context establishment in DTNs. Concretely, we design a scheme that allows users to leverage social contact information to exchange confidential and authentic messages. We then evaluate the proposed scheme by analyzing real-world social network data, simulating communication scenarios, and through an informal security analysis.

5PM: Secure pattern matching

In this paper we consider the problem of secure pattern matching that allows single-character wildcards and substring matching in the malicious stand-alone setting. Our protocol, called 5PM, is executed between two parties: Server, holding a text of length n, and Client, holding a pattern of length m to be matched against the text, where our notion of matching is more general than traditionally considered and includes non-binary alphabets, non-binary Hamming distance and non-binary substring matching.5PM is the first secure expressive pattern matching protocol designed to optimize round complexity by carefully specifying the entire protocol round by round. 5PM requires only eight rounds in the malicious static corruptions model. In the malicious model, 5PM requires O((m+n)k2) communication complexity and O(m+n) encryptions, where m is the pattern length and n is the text length. Further, 5PM can hide pattern size with no asymptotic additional costs in either computation or bandwidth.

Proposal for a cross-layer coordination framework for next generation wireless systems

Cross-Layer design has been the focus of several recent research efforts. Due to the highly variable nature of the links used in wireless communication systems and the resource-poor nature of the wireless mobile devices, there have been multiple research efforts to improve the performance of the protocol stack by allowing cross-layer interaction in wireless systems. Cross-layer interaction means allowing communication of a layer with any other possibly non-adjacent layer in the protocol stack. Several issues related to the cross-layer design paradigm need to be addressed before it can achieve its promises. One of these issues is to have a well defined framework that manages the interaction between the different layers of the protocol stack, such that the modularity of the stack is preserved while still achieving the flexibility and adaptability which cross-layer design promises. This paper addresses this issue by proposing a cross-layer coordination framework for next generation wireless systems. The proposed framework enables the interaction between non-adjacent layers in a systematic organized way while preserving the modularity of each layer. The proposed framework addresses some of the concerns stated in recent research about cross-layer design. We believe that the existence of such a framework will ease the development of cross-layer design schemes.

5PM: secure pattern matching

In this paper we consider the problem of secure pattern matching that allows single character wildcards and substring matching in the malicious (stand-alone) setting. Our protocol, called 5PM, is executed between two parties: Server, holding a text of length n, and Client, holding a pattern of length m to be matched against the text, where our notion of matching is more general and includes non-binary alphabets, non-binary Hamming distance and non-binary substring matching. 5PM is the first protocol with communication complexity sub-linear in circuit size to compute non-binary substring matching in the malicious model (general MPC has communication complexity which is at least linear in the circuit size). 5PM is also the first sublinear protocol to compute non-binary Hamming distance in the malicious model. Additionally, in the honest-but-curious (semi-honest) model, 5PM is asymptotically more efficient than the best known scheme when amortized for applications that require single charcter wildcards or substring pattern matching. 5PM in the malicious model requires O((m+n)k2) bandwidth and O(m+n) encryptions, where m is the pattern length and n is the text length. Further, 5PM can hide pattern size with no asymptotic additional costs in either computation or bandwidth. Finally, 5PM requires only 2 rounds of communication in the honest-but-curious model and 8 rounds in the malicious model. Our techniques reduce pattern matching and generalized Hamming distance problem to a novel linear algebra formulation that allows for generic solutions based on any additively homomorphic encryption. We believe our efficient algebraic techniques are of independent interest.

Communication-Optimal Proactive Secret Sharing for Dynamic Groups

Proactive secret sharing (PSS) schemes are designed for settings where long-term confidentiality of secrets is required, specifically, when all participating parties may eventually be corrupted. PSS schemes periodically refresh secrets and reset corrupted parties to an uncorrupted state; in PSS the corruption threshold of parties is replaced with a corruption rate which cannot be violated. In dynamic proactive secret sharing (DPSS) the group of participating parties can vary during the course of execution. Accordingly, DPSS is ideal when the set of participating parties changes over the lifetime of the secret or where removal of parties is necessary if they become severely corrupted. This paper presents the first DPSS scheme with optimal amortized per-secret communication in the number of parties, n: This paper requires O(1) communication, as compared to \(O(n^4)\) or \(\exp (n)\) in previous work. We present perfectly and statistically secure schemes with near-optimal threshold in each case. We also describe how to construct a communication-efficient dynamic proactively-secure multiparty computation (DPMPC) protocol which achieves the same thresholds.

Blindfolded Data Search via Secure Pattern Matching

Balancing security and privacy concerns with information sharing is a top priority for corporations, law enforcement agencies, governments, and other organizations. Secure pattern matching (SPM) addresses some of the challenges faced in sharing and searching private data.

Agent societies and social networks for ubiquitous computing

Abstract In ubiquitous computing environments, providing appropriate services and information to users at the right place in the right way is challenging for many reasons: different user interests, heterogeneous devices and services, dynamic networks, information overload, or differing privacy levels, for example. Agent technology is a paradigm expected to play an increasing role in complex computing environments, and due to the increasing popularity of social networking services, we expect to see the convergence of agent and social web technologies. The goal of this theme issue is to bring together state-of-the-art research contributions that examine the convergence of agent technologies and social networks for ubiquitous computing.

Secure and privacy-preserving querying of content in MANETs

Ensuring security and privacy of content in a mobile ad-hoc network (MANET) is a challenging problem, especially when that content is distributed over the network using some form of peer-to-peer dissemination scheme. Since cooperation among nodes is vital in MANETs, the capture or compromise of a single node not only exposes locally cached content, but also allows an adversary to interrogate the network with the authority of an insider, acquiring important information such as content access patterns, popularity and location. Previous work in MANETs has predominantly focused on providing solutions for security and anonymity of routing protocols, confidentiality, and key management. In this paper, we present protocols that provide the ability to securely and privately locate content for two common peer-to-peer dissemination operations: publish/subscribe (content PUSH), and direct query (content PULL).

An architecture for a resilient cloud computing infrastructure

This paper proposes an architecture for a resilient cloud computing infrastructure that provably maintains cloud functionality against persistent successful corruptions of cloud nodes. The architecture is composed of a self-healing software mechanism for the entire cloud, as well as hardware-assisted regeneration of compromised (or faulty) nodes from a pristine state. Such an architecture aims to secure critical distributed cloud computations well beyond the current state of the art by tolerating, in a seamless fashion, a continuous rate of successful corruptions up to certain corruption rate limit, e.g., 30% of all cloud nodes may be corrupted within a tunable window of time. The proposed architecture achieves these properties based on a principled separation of distributed task supervision from the computation of user-defined jobs. The task supervision and enduser communication are performed by a new software mechanism called the Control Operations Plane (COP), which builds a trustworthy and resilient, self-healing cloud computing infrastructure out of the underlying untrustworthy and faulty hosts. The COP leverages provably-secure cryptographic protocols that are efficient and robust in the presence of many corrupted participants - such a cloud regularly and unobtrusively refreshes itself by restoring COP nodes from a pristine state at regular intervals.