Practical Security Analysis of Zero-Knowledge Proof Circuits

As privacy-sensitive applications based on zero-knowledge proofs (ZKPs) gain increasing traction, there is a pressing need to detect vulnerabilities in ZKP circuits. This paper studies common vulnerabilities in Circom (the most popular domain-specific language for ZKP circuits) and describes a static analysis framework for detecting these vulnerabilities. Our technique operates over an abstraction called the circuit dependence graph (CDG) that captures key properties of the circuit and allows expressing semantic vulnerability patterns as queries over the CDG abstraction. We have implemented 9 different detectors using this framework and perform an experimental evaluation on over 258 circuits from popular Circom projects on Github. According to our evaluation, these detectors can identify vulnerabilities, including previously unknown ones, with high precision and recall

Privacy in the Smart City - Applications, Technologies, Challenges and Solutions

Many modern cities strive to integrate information technology into every aspect of city life to create so-called smart cities. Smart cities rely on a large number of application areas and technologies to realize complex interactions between citizens, third parties, and city departments. This overwhelming complexity is one reason why holistic privacy protection only rarely enters the picture. A lack of privacy can result in discrimination and social sorting, creating a fundamentally unequal society. To prevent this, we believe that a better understanding of smart cities and their privacy implications is needed. We therefore systematize the application areas, enabling technologies, privacy types, attackers and data sources for the attacks, giving structure to the fuzzy term “smart city”. Based on our taxonomies, we describe existing privacy-enhancing technologies, review the state of the art in real cities around the world, and discuss promising future research directions. Our survey can serve as a reference guide, contributing to the development of privacy-friendly smart cities

TLS on Android – Evolution over the last decade

Mobile Geräte und mobile Plattformen sind omnipräsent. Android hat sich zum bedeutendsten mobilen Betriebssystem entwickelt und bietet Milliarden Benutzer:innen eine Plattform mit Millionen von Apps. Diese bieten zunehmend Lösungen für alltägliche Probleme und sind aus dem Alltag nicht mehr wegzudenken. Mobile Apps arbeiten dazu mehr und mehr mit persönlichen sensiblen Daten, sodass ihr Datenverkehr ein attraktives Angriffsziel für Man-in-the-Middle-attacks (MitMAs) ist. Schutz gegen solche Angriffe bieten Protokolle wie Transport Layer Security (TLS) und Hypertext Transfer Protocol Secure (HTTPS), deren fehlerhafter Einsatz jedoch zu ebenso gravierenden Unsicherheiten führen kann. Zahlreiche Ereignisse und frühere Forschungsergebnisse haben diesbezüglich Schwachstellen in Android Apps gezeigt. Diese Arbeit präsentiert eine Reihe von Forschungsbeiträgen, die sich mit der Sicherheit von Android befassen. Der Hauptfokus liegt dabei auf der Netzwerksicherheit von Android Apps. Hierbei untersucht diese Arbeit verschiedene Möglichkeiten zur Verbesserung der Netzwerksicherheit und deren Erfolg, wobei sie die Situation in Android auch mit der generellen Evolution von Netzwerksicherheit in Kontext setzt. Darüber hinaus schließt diese Arbeit mit einer Erhebung der aktuellen Situation und zeigt Möglichkeiten zur weiteren Verbesserung auf.Smart devices and mobile platforms are omnipresent. Android OS has evolved to become the most dominating mobile operating system on the market with billions of devices and a platform with millions of apps. Apps increasingly offer solutions to everyday problems and have become an indispensable part of people’s daily life. Due to this, mobile apps carry and handle more and more personal and privacy-sensitive data which also involves communication with backend or third party services. Due to this, their network traffic is an attractive target for Man-in-the-Middle-attacks (MitMAs). Protection against such attacks is provided by protocols such as Transport Layer Security (TLS) and Hypertext Transfer Protocol Secure (HTTPS). Incorrect use of these, however, can impose similar vulnerabilities lead to equally serious security issues. Numerous incidents and research efforts have featured such vulnerabilities in Android apps in this regard. This thesis presents a line of research addressing security on Android with a main focus on the network security of Android apps. This work covers various approaches for improving network security on Android and investigates their efficacy as well as it puts findings in context with the general evolution of network security in a larger perspective. Finally, this work concludes with a survey of the current state of network security in Android apps and envisions directions for further improvement

Advanced Security Analysis for Emergent Software Platforms

Emergent software ecosystems, boomed by the advent of smartphones and the Internet of Things (IoT) platforms, are perpetually sophisticated, deployed into highly dynamic environments, and facilitating interactions across heterogeneous domains. Accordingly, assessing the security thereof is a pressing need, yet requires high levels of scalability and reliability to handle the dynamism involved in such volatile ecosystems. This dissertation seeks to enhance conventional security detection methods to cope with the emergent features of contemporary software ecosystems. In particular, it analyzes the security of Android and IoT ecosystems by developing rigorous vulnerability detection methods. A critical aspect of this work is the focus on detecting vulnerable and unsafe interactions between applications that share common components and devices. Contributions of this work include novel insights and methods for: (1) detecting vulnerable interactions between Android applications that leverage dynamic loading features for concealing the interactions; (2) identifying unsafe interactions between smart home applications by considering physical and cyber channels; (3) detecting malicious IoT applications that are developed to target numerous IoT devices; (4) detecting insecure patterns of emergent security APIs that are reused from open-source software. In all of the four research thrusts, we present thorough security analysis and extensive evaluations based on real-world applications. Our results demonstrate that the proposed detection mechanisms can efficiently and effectively detect vulnerabilities in contemporary software platforms. Advisers: Hamid Bagheri and Qiben Ya

Understanding Flaws in the Deployment and Implementation of Web Encryption

In recent years, the web has switched from using the unencrypted HTTP protocol to using encrypted communications. Primarily, this resulted in increasing deployment of TLS to mitigate information leakage over the network. This development has led many web service operators to mistakenly think that migrating from HTTP to HTTPS will magically protect them from information leakage without any additional effort on their end to guar- antee the desired security properties. In reality, despite the fact that there exists enough infrastructure in place and the protocols have been “tested” (by virtue of being in wide, but not ubiquitous, use for many years), deploying HTTPS is a highly challenging task due to the technical complexity of its underlying protocols (i.e., HTTP, TLS) as well as the complexity of the TLS certificate ecosystem and this of popular client applications such as web browsers. For example, we found that many websites still avoid ubiquitous encryption and force only critical functionality and sensitive data access over encrypted connections while allowing more innocuous functionality to be accessed over HTTP. In practice, this approach is prone to flaws that can expose sensitive information or functionality to third parties. Thus, it is crucial for developers to verify the correctness of their deployments and implementations. In this dissertation, in an effort to improve users’ privacy, we highlight semantic flaws in the implementations of both web servers and clients, caused by the improper deployment of web encryption protocols. First, we conduct an in-depth assessment of major websites and explore what functionality and information is exposed to attackers that have hijacked a user’s HTTP cookies. We identify a recurring pattern across websites with partially de- ployed HTTPS, namely, that service personalization inadvertently results in the exposure of private information. The separation of functionality across multiple cookies with different scopes and inter-dependencies further complicates matters, as imprecise access control renders restricted account functionality accessible to non-secure cookies. Our cookie hijacking study reveals a number of severe flaws; for example, attackers can obtain the user’s saved address and visited websites from e.g., Google, Bing, and Yahoo allow attackers to extract the contact list and send emails from the user’s account. To estimate the extent of the threat, we run measurements on a university public wireless network for a period of 30 days and detect over 282K accounts exposing the cookies required for our hijacking attacks. Next, we explore and study security mechanisms purposed to eliminate this problem by enforcing encryption such as HSTS and HTTPS Everywhere. We evaluate each mechanism in terms of its adoption and effectiveness. We find that all mechanisms suffer from implementation flaws or deployment issues and argue that, as long as servers continue to not support ubiquitous encryption across their entire domain, no mechanism can effectively protect users from cookie hijacking and information leakage. Finally, as the security guarantees of TLS (in turn HTTPS), are critically dependent on the correct validation of X.509 server certificates, we study hostname verification, a critical component in the certificate validation process. We develop HVLearn, a novel testing framework to verify the correctness of hostname verification implementations and use HVLearn to analyze a number of popular TLS libraries and applications. To this end, we found 8 unique violations of the RFC specifications. Several of these violations are critical and can render the affected implementations vulnerable to man-in-the-middle attacks