Routing in anonymous networks as a means to prevent traffic analysis

Traditionally, traffic analysis is something that has been used to measure and keep track of a network's situation regarding network congestion, networking hardware failures, etc. However, largely due to commercial interests such as targeted advertisement, traffic analysis techniques can also be used to identify and track a single user's movements within the Internet. To counteract this perceived breach of privacy and anonymity, several counters have been developed over time, e.g. proxies used to obfuscate the true source of traffic, making it harder for others to pinpoint your location. Another approach has been the development of so called anonymous overlay networks, application-level virtual networks running on top of the physical IP network. The core concept is that by the way of encryption and obfuscation of traffic patterns, the users of such anonymous networks will gain anonymity and protection against traffic analysis techniques. In this master's thesis we will be taking a look at how message forwarding or packet routing in IP networks functions and how this is exploited in different analysis techniques to single out a visitor to a website or just someone with a message being forwarded through a network device used for traffic analysis. After that we will discuss some examples of anonymous overlay networks and see how well they protect their users from traffic analysis, and how do their respective models hold up against traffic analysis attacks from a malicious entity. Finally, we will present a case study about Tor network's popularity by running a Tor relay node and gathering information on how much data the relay transmits and from where does the traffic originate. CCS-concepts: - Security and privacy ~ Privacy protections - Networks ~ Overlay and other logical network structures - Information systems ~ Traffic analysi

Big Data SAVE: Secure Anonymous Vault Environment

There has been great progress in taming the volume, velocity and variation of Big Data. Its volume creates need for increased storage space and improved data handling. Its velocity is concern for the speed and efficiency of applied algorithms and processes. Its variation requires flexibility to handle assorted data-types. However, as with many emerging fields, security has taken a backseat to benchmarks. This has led to retrofitting traditional security techniques ill-suited for Big Data protection, or high-performance setups exposed to data breach. Proposed is an innovative storage system that can provide large-scale, low-overhead data security, akin to safe-deposit boxes. This approach allows for anonymously-shared storage space, discrete levels of access, plausible deniability, and customizable degrees of overall protection (including warrant-proof). A promising factor of this new model is the use of a simple encryption algorithm (proven faster than industry-standard ciphers), that provides inherent attack resiliency and strong backward secrecy

Client-side privacy-enhancing technologies in web search

Els motors de cerca (En anglès, Web Search Engines - WSEs-), són eines que permeten als usuaris localitzar informació específica a Internet. Un dels objectius dels WSEs és retornar els resultats que millor coincideixen amb els interessos de cada usuari. Amb aquesta finalitat, l'WSEs recull i analitza l' historial de cerca per construir perfils. Com a resultat, un usuari que envia una certa consulta rebrà els resultats més interessants en les primeres posicions. Encara que proporcionen un servei molt útil, també representen una amenaça per a la privacitat dels seus usuaris. Es construeixen els perfils basats en la història de les consultes i altres dades relacionades que poden contenir informació personal i privada. Per evitar aquesta amenaça de privacitat, és necessari establir mecanismes per a la protecció de la privacitat dels usuaris dels motors de cerca. Actualment, hi ha diverses solucions en la literatura per proporcionar privacitat a aquests usuaris. Un dels objectius d'aquest estudi és analitzar les solucions existents, estudiar les seves diferències i els avantatges i inconvenients de cada proposta. Llavors, basat en l'estat de l'art, presentem noves propostes per protegir la privadesa dels usuaris. Més concretament, aquesta tesi proposa tres protocols per preservar la privacitat dels usuaris en la cerca web. La idea general és distribuir als usuaris en grups on intercanvi consultes, com a mètode d'ofuscació ocultar les consultes reals de cada usuari. El primer protocol distribuït que proposem es centra en la reducció del temps d'espera de consulta, és a dir, el temps que cada membre del grup ha d'esperar per rebre els resultats de la seva consulta. El segon protocol proposat millora les propostes anteriors ja que resisteix els atacs interns, i obté millors resultats que les propostes similars en termes de càlcul i comunicació. La tercera proposta és un protocol P2P, on els usuaris estan agrupats segons les seves preferències. Això permet ocultar els perfils d'usuari però conservar els interessos generals. En conseqüència, el motor de cerca és capaç de classificar millor els resultats de les seves consultes.Los motores de búsqueda (en inglés, Web Search Engines -WSEs-) son herramientas que permiten a los usuarios localizar información específica en Internet. Uno de los objetivos de los WSEs es devolver los resultados que mejor coinciden con los intereses de cada usuario. Para ello, los WSEs recogen y analizan el historial de búsqueda de los usuarios para construir perfiles. Como resultado, un usuario que envía una cierta consulta recibirá los resultados más interesantes en las primeras posiciones. Aunque ofrecen un servicio muy útil, también representan una amenaza para la privacidad de sus usuarios. Los perfiles se construyen a partir del historial de consultas y otros datos relacionados que pueden contener información privada y personal. Para evitar esta amenaza de privacidad, es necesario establecer mecanismos de protección de privacidad de motores de búsqueda. En la actualidad, existen varias soluciones en la literatura para proporcionar privacidad a estos usuarios. Uno de los objetivos de este trabajo es examinar las soluciones existentes, analizando sus diferencias y las ventajas y desventajas de cada propuesta. Después, basándonos en el estado del arte actual, presentamos nuevas propuestas que protegen la privacidad de los usuarios. Más concretamente, esta tesis doctoral propone tres protocolos que preservan la privacidad de los usuarios en las búsquedas web. La idea general es distribuir a los usuarios en grupos donde intercambian sus consultas, como método de ofuscación para ocultar las consultas reales de cada usuario. El primer protocolo distribuido que proponemos se centra en reducir el tiempo de espera de la consulta, es decir, el tiempo que cada miembro del grupo tiene que esperar para recibir los resultados de la consulta. El segundo protocolo propuesto mejora anteriores propuestas porque resiste ataques internos, mejorando propuestas similares en términos de cómputo y comunicación. La tercera propuesta es un protocolo P2P, donde los usuarios se agrupan según sus preferencias. Esto permite ofuscar los perfiles de los usuarios pero conservando a sus intereses generales. En consecuencia, el WSE es capaz de clasificar mejor los resultados de sus consultas.Web search engines (WSEs) are tools that allow users to locate specific information on the Internet. One of the objectives of WSEs is to return the results that best match the interests of each user. For this purpose, WSEs collect and analyze users’ search history in order to build profiles. Consequently, a profiled user who submits a certain query will receive the results which are more interesting for her in the first positions. Although they offer a very useful service, they also represent a threat for their users’ privacy. Profiles are built from past queries and other related data that may contain private and personal information. In order to avoid this privacy threat, it is necessary to provide privacy-preserving mechanisms that protect users. Nowadays, there exist several solutions that intend to provide privacy in this field. One of the goals of this work is to survey the current solutions, analyzing their differences and remarking the advantages and disadvantages of each approach. Then, based on the current state of the art, we present new proposals that protect users’ privacy. More specifically, this dissertation proposes three different privacy-preserving multi-party protocols for web search. A multi-party protocol for web search arranges users into groups where they exchange their queries. This serves as an obfuscation method to hide the real queries of each user. The first multi-party protocol that we propose focuses on reducing the query delay. This is the time that every group member has to wait in order to receive the query results. The second proposed multi-party protocol improves current literature because it is resilient against internal attacks, outperforming similar proposals in terms of computation and communication. The third proposal is a P2P protocol, where users are grouped according to their preferences. This allows to obfuscate users’ profiles but conserving their general interests. Consequently, the WSE is able to better rank the results of their queries

Evaluating Methods for Privacy-Preserving Data Sharing in Genomics

The availability of genomic data is often essential to progress in biomedical re- search, personalized medicine, drug development, etc. However, its extreme sensitivity makes it problematic, if not outright impossible, to publish or share it. In this dissertation, we study and build systems that are geared towards privacy preserving genomic data sharing. We first look at the Matchmaker Exchange, a platform that connects multiple distributed databases through an API and allows researchers to query for genetic variants in other databases through the network. However, queries are broadcast to all researchers that made a similar query in any of the connected databases, which can lead to a reluctance to use the platform, due to loss of privacy or competitive advantage. In order to overcome this reluctance, we propose a framework to support anonymous querying on the platform. Since genomic data’s sensitivity does not degrade over time, we analyze the real-world guarantees provided by the only tool available for long term genomic data storage. We find that the system offers low security when the adversary has access to side information, and we support our claims by empirical evidence. We also study the viability of synthetic data for privacy preserving data sharing. Since for genomic data research, the utility of the data provided is of the utmost importance, we first perform a utility evaluation on generative models for different types of datasets (i.e., financial data, images, and locations). Then, we propose a privacy evaluation framework for synthetic data. We then perform a measurement study assessing state-of-the-art generative models specifically geared for human genomic data, looking at both utility and privacy perspectives. Overall, we find that there is no single approach for generating synthetic data that performs well across the board from both utility and privacy perspectives

Settling for limited privacy: how much does it help?

This thesis explores practical and theoretical aspects of several privacy-providing technologies, including tools for anonymous web-browsing, verifiable electronic voting schemes, and private information retrieval from databases. State-of-art privacy-providing schemes are frequently impractical for implementational reasons or for sheer information-theoretical reasons due to the amount of information that needs to be transmitted. We have been researching the question of whether relaxing the requirements on such schemes, in particular settling for imperfect but sufficient in real-world situations privacy, as opposed to perfect privacy, may be helpful in producing more practical or more efficient schemes. This thesis presents three results. The first result is the introduction of caching as a technique for providing anonymous web-browsing at the cost of sacrificing some functionality provided by anonymizing systems that do not use caching. The second result is a coercion-resistant electronic voting scheme with nearly perfect privacy and nearly perfect voter verifiability. The third result consists of some lower bounds and some simple upper bounds on the amount of communication in nearly private information retrieval schemes; our work is the first in-depth exploration of private information schemes with imperfect privacy