Open Access

Jonas Spenger

• We present the tamper-resistant broadcast abstraction of the Bitcoin blockchain, and show how it can be used to implement tamper-resistant replicated state machines. The tamper-resistant broadcast abstraction provides functionality to: broadcast, deliver, and verify messages. The tamper-resistant property ensures: 1) the probabilistic protection against byzantine behaviour, and 2) the probabilistic verifiability that no tampering has occurred. In this work, we study various tamper-resistant broadcast protocols for: different environmental models (public/permissioned, bounded/unbounded, byzantine fault tolerant (BFT)/non-BFT, native/non-native); as well as different properties, such as ordering guarantees (FIFO-order, causal-order, total-order), and delivery guarantees (validity, agreement, uniform). This way, we can match the protocol to the required environment model and consistency model of the replicated state machine. We implemented the tamper-resistant broadcast abstraction as a proof of concept. The results show that the implemented tamper-resistant broadcast protocols can compete on throughput and latency with other state-of-the-art broadcast technologies. Use cases, such as a tamper-resistant file system, supply chain tracking, and a timestamp server highlight the expressiveness of the abstraction. In conclusion, the tamper-resistant broadcast protocols provide a powerful interface, with clear semantics and tunable settings, enabling the design of tamper-resistant applications.