Probabilistic Consensus of the Blockchain Protocol

We introduce a temporal epistemic logic with probabilities as an extension of temporal epistemic logic. This extension enables us to reason about properties that characterize the uncertain nature of knowledge, like “agent a will with high probability know after time s same fact”. To define semantics for the logic we enrich temporal epistemic Kripke models with probability functions defined on sets of possible worlds. We use this framework to model and reason about probabilistic properties of the blockchain protocol, which is in essence probabilistic since ledgers are immutable with high probabilities. We prove the probabilistic convergence for reaching the consensus of the protocol

Quantitative verification of gossip protocols for certificate transparency

Certificate transparency is a promising solution to publicly auditing Internet certificates. However, there is the potential of split-world attacks, where users are directed to fake versions of the log where they may accept fraudulent certificates. To ensure users are seeing the same version of a log, gossip protocols have been designed where users share and verify log-generated data. This thesis proposes a methodology of evaluating such protocols using probabilistic model checking, a collection of techniques for formally verifying properties of stochastic systems. It also describes the approach to modelling and verifying the protocols and analysing several aspects, including the success rate of detecting inconsistencies in gossip messages and its efficiency in terms of bandwidth. This thesis also compares different protocol variants and suggests ways to augment the protocol to improve performances, using model checking to verify the claims. To address uncertainty and unscalability issues within the models, this thesis shows how to transform models by allowing the probability of certain events to lie within a range of values, and abstract them to make the verification process more efficient. Lastly, by parameterising the models, this thesis shows how to search possible model configurations to find the worst-case behaviour for certain formal properties

Augmenting Zero Trust Architecture to endpoints using Distributed Ledger Technologies and Blockchain

With the increasing adoption of cloud computing and remote working, traditional perimeter-based security models are no longer sufficient to protect organizations' digital assets. The need for a more robust security framework led to the emergence of Zero Trust Architecture (ZTA), which challenges the notion of inherent trust and emphasizes the importance of verifying endpoints, users, and applications. However, within ZTA, the already authenticated and authorized communication channel on an endpoint poses a critical vulnerability, making it the Achilles' heel of the architecture [1]. Once compromised, even with valid credentials and authorized access, an endpoint can become a gateway for attackers to move laterally and access sensitive resources. Addressing the vulnerability of endpoints within ZTA is crucial to bolster overall security. By mitigating the risks associated with compromised endpoints, organizations can prevent unauthorized access, privilege escalation, and potential data breaches. Traditional security measures, such as firewalls, antivirus technologies, and Intrusion Detection and Prevention Systems (IDS/IPS), have become less effective in the face of evolving threats and complex network infrastructures. Perimeter-based security models are gradually being replaced by ZTA, which focuses on identity-based perimeters and continuous verification. To enhance endpoint security within ZTA, this research introduces the Blockchain-enabled Intrusion Detection and Prevention System (BIDPS). By integrating blockchain technology, the BIDPS aims to detect and prevent attacker techniques at an early stage before lateral movement occurs. Furthermore, the BIDPS shifts the trust from compromised endpoints to the immutable and transparent nature of the blockchain, creating an explicit system of trust. Through a systematic design and development methodology, a prototype of the BIDPS was created. Extensive testing against various Advanced Persistent Threat (APT) attacks demonstrated the system's high success rate in defending against such attacks. Additionally, novel strategies and performance-enhancing mechanisms were implemented to improve the effectiveness and efficiency of the BIDPS [2]. The BIDPS was evaluated through a combination of observational analysis and A/B testing methodologies. The evaluation confirmed the BIDPS's effectiveness in detecting and preventing malicious activities, as well as its improved performance compared to traditional security measures. The research outcomes validate the viability of the BIDPS as a solution to enhance endpoint security within ZTA. Conclusively, the integration of blockchain technology into ZTA, as exemplified by the BIDPS, offers a promising approach to mitigate the vulnerability of endpoints and reinforce the security of modern IT environments