Towards Private and Compliable Blockchain Applications

Abstract

Privacy and compliance are essential pillars of modern society, with privacy safeguarding individual autonomy and compliance ensuring adherence to norms and regulations. Effective compliance must uphold privacy to ensure trust and legitimacy, while privacy frameworks depend on compliance to implement safeguards and ensure accountability. The transparent nature of emerging blockchain technology presents unique challenges to balancing these principles, especially in regulated sectors.

To study the privacy and compliance issues in blockchain systems, this thesis focuses on three key domains, each exemplified by a representative application. For each application, it provides concrete and efficient constructions. Additionally, it introduces a novel cryptographic tool, serving as a building block for developing private and compliant blockchain applications.

The thesis begins by addressing privacy concerns in centralized cryptocurrency exchange platforms, proposing a privacy-preserving exchange system that achieves user anonymity and regulatory compliance simultaneously. Next, it focuses on privacy as a regulatory mandate, presenting a secure dark pool system that employs secure multiparty computation to preserve privacy while ensuring market stability. It then explores scenarios where privacy is exploited, proposing a novel mechanism to prevent gas fee concurrency attacks in relay systems, ensuring fair compensation without compromising anonymity. This work also introduces predicate aggregate signatures motivated by blockchain governance, a new cryptographic primitive that integrates privacy protection into compliance settings, enabling anonymous aggregation of signatures while maintaining compliance with public predicates.

Through these applications and the fundamental tool, this thesis demonstrates how privacy and compliance can be balanced using innovative cryptographic techniques, offering practical solutions for real-world blockchain applications.