InfoSec Seminar: Apostolos Pyrgelis & Dr Mohammad Hajiabadi

Speaker: Apostolos Pyrgelis & Dr Mohammad Hajiabadi
UCL Contact: Jonathan Bootle (Visitors from outside UCL please email in advance).
Date/Time: 27 Oct 16, 16:00 - 17:00
Venue: Gordon Street (25) Maths 505

Abstract

Apostolos Pyrgelis

Privacy-Friendly Mobility Analytics using Aggregate Location Data

Location data can be extremely useful to study commuting patterns and disruptions, as well as to predict real-time traffic volumes. At the same time, however, the fine-grained collection of user locations raises serious privacy concerns, as this can reveal sensitive information about the users, such as, life style, political and religious inclinations, or even identities. In our paper, we study the feasibility of crowd-sourced mobility analytics over aggregate location information: users periodically report their location, using a privacy-preserving aggregation protocol, so that the server can only recover aggregates -- i.e., how many, but not which, users are in a region at a given time. We experiment with real-world mobility datasets obtained from the Transport For London authority and the San Francisco Cabs network, and present a novel methodology based on time series modeling that is geared to forecast traffic volumes in regions of interest and to detect mobility anomalies in them. In the presence of anomalies, we also make enhanced traffic volume predictions by feeding our model with additional information from correlated regions. Finally, we present and evaluate a mobile app prototype, called Mobility Data Donors (MDD), in terms of computation, communication, and energy overhead, demonstrating the real-world deployability of our techniques.

Dr Mohammad Hajiabadi

Limitations of black-box constructions in cryptography

Since much of modern cryptography is based on unproven assumptions a central goal in crypto is to base primitives on the weakest possible assumptions. Most cryptographic constructions are black-box in the sense that, roughly speaking, the constructed object uses the base object as an oracle, without assuming anything beyond the input-output behavior of the base object. Starting with the seminal paper of Impagliazzo and Rudich (1989) there has been a large body of work showing that certain cryptographic primitives cannot be built based on certain others in a black-box way.

I'll give an overview of some of the black-box separation models used in the literature. If time permits, I'll discuss one of the results of my PhD work, showing a black-box separation between key-dependent-message-secure (KDM-secure) public-key encryption and semantically-secure public-key encryption.

Apostolos Pyrgelis & Dr Mohammad Hajiabadi

Dr Mohammad Hajiabadi

Mohammad Hajiabadi has recently (September 2016) joined the security group of UCL, working with Jens Groth. He completed his PhD in Computer Science at the University of Victoria, Canada, under the supervision of Bruce Kapron. His main areas of research include foundations of cryptography and applications of formal methods in cryptography.