Attacking transaction relay in MimbleWimble blockchains

Blockchain-based networks are often concerned with privacy. Two common types of privacy in blockchain networks are (1) transaction source privacy, and (2) transaction content privacy. Research has shown that Bitcoin, the most prominent cryptocurrency, cannot easily provide these privacy types. Hence, new protocols have been proposed. For example, Dandelion++ is a solution to the source privacy vulnerability in Bitcoin. Practical systems, however, need to provide multiple privacy guarantees at the same time. To the best of our knowledge, source privacy and content privacy have not been considered simultaneously in the literature. We conjecture that cryptocurrencies that use Dandelion++ for transaction relay could be susceptible to attacks against both types of privacy and also to performance attacks. Our focus in this project is on the implementations of the MimbleWimble cryptocurrency protocol such as Beam. We have designed and implemented three different attacks against these existing privacy-focused protocols. In the first attack, the adversary uses information obtained from an incoming transaction for improved detection of the transaction source. In the second attack, to increase the latency of an incoming transaction, the adversary adds an excessive delay before forwarding the transaction. In the third attack, the adversary exploits the aggregation protocol in MimbleWimble to launch a denial of service attack on an incoming transaction. We have validated our proposed attacks in a private test network of Beam nodes and a network simulator.Science, Faculty ofComputer Science, Department ofGraduat