Numerous mobile applications have the potential to collect and share userspecific information on top of the essential data handling. This is made possible through poor application design and its improper implementation. The lack of security and privacy in an application is of main concern since the spread of sensitive and personal information can cause both physical and emotional harm, if it is being shared with unauthorized people. This thesis investigates how to confidentially transfer user information in such a way that the user remains anonymous and untraceable in a mobile application. In order to achieve that, the user will first authenticate itself to a third party, which provides the user with certificates or random generated tokens. The user can then use this as its communication credentials towards the server, which will be made through the Tor network. Further, when the connection is established, the WiFi details are sent periodically to the server without the user initiating the action. The results show that it is possible to establish connection, both with random tokens and certificates. The random tokens took less time to generate compared to the certificate, however the certificate took less time to verify, which balances off the whole performance of the system. Moreover, the results show that the implementation of Tor is working since it is possible for the system to hide the real IP address, and provide a random IP address instead. However, the communication is slower when Tor is used which is the cost for achieving anonymity and improving the privacy of the user. Conclusively, this thesis proves that combining proper implementation and good application design improves the security in the application thereby protecting the users’  privacy. / Många mobilapplikationer har möjlighet att samla in och dela användarspecifik information, utöver den väsentliga datahanteringen. Det här problemet möjliggörs genom dålig applikationsdesign och felaktig implementering. Bristen på säkerhet och integritet i en applikation är därför kritisk, eftersom spridning av känslig och personlig information kan orsaka både fysisk och emotionell skada, om den delas med obehöriga personer. Denna avhandling undersöker hur man konfidentiellt kan överföra användarinformation på ett sätt som tillåter användaren av mobilapplikationen att förbli både anonym och icke spårbar. För att uppnå detta kommer användaren först att behöva autentisera sig till en tredje part, vilket förser användaren med slumpmässigt genererade tecken eller med ett certifikat. Användaren kan sedan använda dessa till att kommunicera med servern, vilket kommer att göras över ett Tor-nätverk. Slutligen när anslutningen upprättats, kommer WiFi-detaljerna att skickas över periodvis till servern, detta sker automatiskt utan att användaren initierar överföringen. Resultatet visar att det är möjligt att skapa en anslutning både med ett certifikat eller med slumpmässiga tecken. Att generera de slumpmässiga tecknen tog mindre tid jämfört med certifikaten, däremot tog certifikaten mindre tid att verifiera än tecknen. Detta resulterade i att de båda metoderna hade en jämn prestanda om man ser över hela systemet. Resultatet visar vidare att det implementeringen av Tor fungerar då det är möjligt för systemet att dölja den verkliga IPadressen och att istället tillhandahålla en slumpmässig IP-adress. Kommunikationen genom Tor gör dock systemet långsammare, vilket är kostnaden för att förbättra användarens integritet och uppnå anonymitet. Sammanfattningsvis visar denna avhandling att genom att kombinera korrekt implementering och bra applikationsdesign kan man förbättra säkerheten i applikationen och därmed skydda användarnas integritet.

No description available.

No description available.

No description available.

No description available.

No description available.

<p>In today’s world, cloud machines store an ever-increasing amount of sensitive user data, but it remains challenging to guarantee the security of our data. This is because a cloud machine’s system software—critical components like the operating system and hypervisor that can access and thus leak user data—is subject to attacks by numerous other tenants and cloud administrators. Trusted execution environments (TEEs) like Intel SGX promise to alter this landscape by leveraging a trusted CPU to create execution contexts (or enclaves) where data cannot be directly accessed by system software. Unfortunately, the protection provided by TEEs cannot guarantee complete data security. In particular, our data remains unprotected if a third-party service (e.g., Yelp) running inside an enclave is adversarial. Moreover, data can be indirectly leaked from the enclave using traditional memory side-channels.</p> <p><br></p> <p>This dissertation takes a significant stride towards strong user data protection in cloud machines using TEEs by defeating the critical threats of adversarial cloud services and memory side-channels. To defeat these threats, we systematically explore both software and hardware designs. In general, we designed software solutions to avoid costly hardware changes and present faster hardware alternatives.</p> <p><br></p> <p>We designed 4 solutions for this dissertation. Our Chancel system prevents data leaks from adversarial services by restricting data access capabilities through robust and efficient compiler-enforced software sandboxing. Moreover, our Obliviate and Obfuscuro systems leverage strong cryptographic randomization and prevent information leakage through memory side-channels. We also propose minimal CPU extensions to Intel SGX called Reparo that directly close the threat of memory side-channels efficiently. Importantly, each designed solution provides principled protection by addressing the underlying root-cause of a problem, instead of enabling partial mitigation.</p> <p><br></p> <p>Finally, in addition to the stride made by our work, future research thrust is required to make TEEs ubiquitous for cloud usage. We propose several such research directions to pursue the essential goal of strong user data protection in cloud machines.</p>

<p>Cyber-Physical Systems (CPS) are integrated systems that consist of the computational and physical components with network communication to support operation in the physical world. My PhD dissertation focuses on the security and reliability of autonomous cyber-physical systems, such as self-driving cars, drones, and underwater robots, that are safety-critical systems based on the seamless integration of cyber and physical components. Autonomous CPS are becoming an integral part of our life. The market for autonomous driving systems is expected to be more than $65 billion by 2026. The security of such CPS is hence critical. Beyond traditional cyber-only computing systems, these complex and integrated CPS have unique characteristics. From the security perspective, they open unique research opportunities since they introduce additional attack vectors and post new challenges that existing cyber-oriented approaches cannot address well. <em>The goal of my research is to build secure and reliable autonomous CPS by bridging the gap between the cyber and physical domains.</em> To this end, my work focuses on fundamental research questions associated with cyber-physical attack and defense, vulnerability discovery and elimination, and post-attack investigation. My approach to solving the problems involves various techniques and interdis- ciplinary knowledge, including program analysis, search-based software engineering, control theory, robotics, and AI/machine learning.</p>

The tremendous success of various wireless applications operating in unlicensed bands has resulted in the overcrowding of those bands. Cognitive radio (CR) is a new technology that enables an unlicensed user to coexist with incumbent users in licensed spectrum bands without inducing interference to incumbent communications. This technology can significantly alleviate the spectrum shortage problem and improve the efficiency of spectrum utilization. Networks consisting of CR nodes (i.e., CR networks)---often called dynamic spectrum access networks or NeXt Generation (XG) communication networks---are envisioned to provide high bandwidth to mobile users via heterogeneous wireless architectures and dynamic spectrum access techniques. In recent years, the operational aspects of CR networks have attracted great research interest. However, research on the security aspects of CR networks has been very limited. In this thesis, we discuss security issues that pose a serious threat to CR networks. Specifically, we focus on three potential attacks that can be launched at the physical or MAC layer of a CR network: primary user emulation (PUE) attack, spectrum sensing data falsification (SSDF) attack, and control channel jamming (CCJ) attack. These attacks can wreak havoc to the normal operation of CR networks. After identifying and analyzing the attacks, we discuss countermeasures. For PUE attacks, we propose a transmitter verification scheme for attack detection. The scheme utilizes the location information of transmitters together with their signal characteristics to verify licensed users and detect PUE attackers. For both SSDF attacks and CCJ attacks, we seek countermeasures for attack mitigation. In particular, we propose Weighted Sequential Probability Ratio Test (WSPRT) as a data fusion technique that is robust against SSDF attacks, and introduce a multiple-rendezvous cognitive MAC (MRCMAC) protocol that is robust against CCJ attacks. Using security analysis and extensive numerical results, we show that the proposed schemes can effectively counter the aforementioned attacks in CR networks. / Ph. D.

<p dir="ltr">Privacy serves as a crucial safeguard for personal autonomy and information, enabling control over personal data and space, fostering trust and security in society, and standing as a cornerstone of democracy by protecting against unwarranted interference. This work aims to enhance Tor, a volunteer-operated network providing privacy to over two million users, by improving its programmability, security, and user-friendliness to support wider adoption and underscore the importance of privacy in protecting individual rights in the digital age.</p><p dir="ltr">Addressing Tor's limitations in adapting to new services and threats, this thesis introduces programmable middleboxes, enabling users to execute complex functions on Tor routers to enhance anonymity, security, and performance. This architecture, called Bento, is designed to secure middleboxes from harmful functions and vice versa, making Tor more flexible and efficient.</p><p dir="ltr">Many of the attacks on Tor's anonymity occur when an adversary can intercept a user’s traffic; it is thus useful to limit how much of a user's traffic can enter potentially adversarial networks. We tackle the vulnerabilities of onion services to surveillance and censorship by proposing DeTor_OS, a Bento function enabling geographic avoidance for onion services- which is challenging since no one entity knows the full circuit between user and onion service, providing a method to circumvent adversarial regions and enhance user privacy.</p><p dir="ltr">The final part focuses on improving onion services' usability and security. Despite their importance, these services face high latency, Denial of Service (DoS) and deanonymization attacks due to their content. We introduce CenTor, a Content Delivery Network (CDN) for onion services using Bento, offering replication, load balancing, and content proximity benefits. Additionally, we enhance performance with multipath routing strategies through uTor, balancing performance and anonymity. We quantitatively analyze how geographical-awareness for an onion service CDN and its clients could impact a user’s anonymity- performance versus security tradeoff. Further, we evaluate CenTor on the live Tor network as well as large-scale Shadow simulations.</p><p dir="ltr">These contributions, requiring no changes to the Tor protocol, represent significant advancements in Tor's capabilities, performance, and defenses, demonstrating potential for immediate benefits to the Tor community.</p>