Auditability in Blockchain Systems Using Cryptographic Protocols

Abstract

Enforcement of policy regulations and availability of auditing mechanisms are crucial building blocks for the adoption of distributed payment systems. In this thesis we provide a series of proposals towards implementing such systems (usually based on a blockchain), augmented with such functionalities. We first propose MiniLedger, a new standalone system that provides both auditability and privacy for its users, while achieving near-constant storage requirements by all participants who maintain it. We then propose add-on protocols for the Diem blockchain, a recently developed permissioned payment system, which enables proving assets held by custodial wallets in that system. Then we propose gOTzilla, which enables proving assets owned by organizations or exchanges in permissionless blockchain systems (such as Bitcoin), while remaining efficient even in the case such systems scale to millions of unspent transaction outputs. Finally, we describe BBox-IoT, which provides a way for resource-constrained devices (typically encountered in an Industrial IoT setting) to efficiently sign data, therefore enabling auditing data provenance in a blockchain-based Industrial IoT system.