Optimizing Proactive Measures for Security Operations

Digital security threats may impact governments, businesses, and consumers through intellectual property theft, loss of physical assets, economic damages, and loss of confidence. Significant effort has been placed on technology solutions that can mitigate threat exposure. Additionally, hundreds of years of literature have focused on non-digital, human-centric strategies that proactively allow organizations to assess threats and implement mitigation plans. For both human and technology-centric solutions, little to no prior research exists on the efficacy of how humans employ digital security defenses. Security professionals are armed with commonly adopted "best practices" but are generally unaware of the particular artifacts and conditions (e.g., organizational culture, procurement processes, employee training/education) that may or may not make a particular environment well-suited for employing the best practices. In this thesis, I study proactive measures for security operations and related human factors to identify generalizable optimizations that can be applied for measurable increases in security. Through interview and survey methods, I investigate the human and organizational factors that shape the adoption and employment of defensive strategies. Case studies with partnered organizations and comprehensive evaluations of security programs reveal security gaps that many professionals were previously unaware of --- as well as opportunities for changes in security behaviors to mitigate future risk. These studies highlight that, in exemplar environments, the adoption of proactive security assessments and training programs lead to measurable improvements in organizations' security posture

On Enhancing Security of Password-Based Authentication

Password has been the dominant authentication scheme for more than 30 years, and it will not be easily replaced in the foreseeable future. However, password authentication has long been plagued by the dilemma between security and usability, mainly due to human memory limitations. For example, a user often chooses an easy-to-guess (weak) password since it is easier to remember. The ever increasing number of online accounts per user even exacerbates this problem. In this dissertation, we present four research projects that focus on the security of password authentication and its ecosystem. First, we observe that personal information plays a very important role when a user creates a password. Enlightened by this, we conduct a study on how users create their passwords using their personal information based on a leaked password dataset. We create a new metric---Coverage---to quantify the personal information in passwords. Armed with this knowledge, we develop a novel password cracker named Personal-PCFG (Probabilistic Context-Free Grammars) that leverages personal information for targeted password guessing. Experiments show that Personal-PCFG is much more efficient than the original PCFG in cracking passwords. The second project aims to ease the password management hassle for a user. Password managers are introduced so that users need only one password (master password) to access all their other passwords. However, the password manager induces a single point of failure and is potentially vulnerable to data breach. To address these issues, we propose BluePass, a decentralized password manager that features a dual-possession security that involves a master password and a mobile device. In addition, BluePass enables a hand-free user experience by retrieving passwords from the mobile device through Bluetooth communications. In the third project, we investigate an overlooked aspect in the password lifecycle, the password recovery procedure. We study the password recovery protocols in the Alexa top 500 websites, and report interesting findings on the de facto implementation. We observe that the backup email is the primary way for password recovery, and the email becomes a single point of failure. We assess the likelihood of an account recovery attack, analyze the security policy of major email providers, and propose a security enhancement protocol to help securing password recovery emails by two factor authentication. \newline Finally, we focus on a more fundamental level, user identity. Password-based authentication is just a one-time checking to ensure that a user is legitimate. However, a user\u27s identity could be hijacked at any step. For example, an attacker can leverage a zero-day vulnerability to take over the root privilege. Thus, tracking the user behavior is essential to examine the identity legitimacy. We develop a user tracking system based on OS-level logs inside an enterprise network, and apply a variety of techniques to generate a concise and salient user profile for identity examination

Revisiting the legal regulation of digital identity in the light of global implementation and local difference

This thesis aims to address a vital gap that has emerged in the digital identity regulatory discourse: how can the legal regulation of digital identity mirror the global nature of digital identity and be compatible with national local difference? Digital identity, or the digital representation of an individual, is a complex concept, which manifests in myriad forms (e.g. authenticators, claims, data or information, identifiers, presence, relationship representations and reputation) and natures. As such, it engages a gamut of legal domains ranging from criminal law, constitutional law, human rights law, law of identity schemes, contract law, intellectual property law, tort law and data protection law. Digital identity is global and local in its nature, influence and effects. Yet, the digital identity regulatory discourse has primarily developed in and focussed on the digitally advanced West, leaving out countries like India which are developing strong digital presences, with their own digital identity perceptions and needs. This situation is adverse to the sustained future of digital identity. Thus, the contribution of this thesis lies in filling this gap and preparing the ground for a dialogue between different countries with different national agendas through building international and local awareness of how similarities and differences operate in respect of digital identity, its regulation and providing a modest solution to help preserve the global and local dimensions of digital identity and its regulation. To this end, the thesis carried out comparative legal research on the legal regulation of digital identity using the UK and India as base jurisdictions. The original hypothesis was that that immense differences in the legal regulation of digital identity between the comparator countries would emerge. Yet, though differences were evident, considerable degrees of similarity also emerged, not just on the superficial level of mere identity of rules, but also in legal practice, in large part attributable to India’s penchant for legal transplants. While the transplantation of Western law did not result in a full-scale rejection of the transplanted laws in relation to digital identity in India, there are indications of anomalies caused by the imposition of Western cultural norms through law on an Indian society ill prepared for it. Thus there has resulted a tension between the local and the global, the indigenous and the externally imposed. The challenge is thus to resolve this, taking into account, on the one hand the need to maintain the global nature and relevance of digital identity and the other, the need to accommodate and be responsive to local differences. The thesis proposes a tentative solution called the tri-elemental framework (TeF) which draws from the Indian philosophical and legal concept of dharma (and its elements of Sad Achara, Vyavahara and Prayaschitta) and learns from the most universally relevant digital identity proposal, De Hert’s right to identity. The solution provides one way in which the law regulating digital identity, whatever its nature, can be made sense of and acquire cultural meaning appropriate to local contexts

Practice-Oriented Privacy in Cryptography

While formal cryptographic schemes can provide strong privacy guarantees, heuristic schemes that prioritize efficiency over formal rigor are often deployed in practice, which can result in privacy loss. Academic schemes that do receive rigorous attention often lack concrete efficiency or are difficult to implement. This creates tension between practice and research, leading to deployed privacy-preserving systems that are not backed by strong cryptographic guarantees. To address this tension between practice and research, we propose a practice-oriented privacy approach, which focuses on designing systems with formal privacy models that can effectively map to real-world use cases. This approach includes analyzing existing privacy-preserving systems to measure their privacy guarantees and how they are used. Furthermore, it explores solutions in the literature and analyzes gaps in their models to design augmented systems that apply more clearly to practice. We focus on two settings of privacy-preserving payments and communications. First, we introduce BlockSci, a software platform that can be used to perform analyses on the privacy and usage of blockchains. Specifically, we assess the privacy of the Dash cryptocurrency and analyze the velocity of cryptocurrencies, finding that Dash’s PrivateSend may still be vulnerable to clustering attacks and that a significant fraction of transactions on Bitcoin are “self-churn” transactions. Next, we build a technique for reducing bandwidth in mixing cryptocurrencies, which suffer from a practical limitation: the size of the transaction growing linearly with the size of the anonymity set. Our proposed technique efficiently samples cover traffic from a finite and public set of known values, while deriving a compact description of the resulting transaction set. We show how this technique can be integrated with various currencies and different cover sampling distributions. Finally, we look at the problem of establishing secure communication channels without access to a trusted public key infrastructure. We construct a scheme that uses network latency and reverse turing tests to detect the presence of eavesdroppers, prove our construction secure, and implement it on top of an existing communication protocol. This line of work bridges the gap between theoretical cryptographic research and real-world deployments to bring better privacy-preserving schemes to end users