A Formal Analysis of the Mimblewimble Cryptocurrency Protocol with a Security Approach

A cryptocurrency is a digital currency that enables online transactions for various products and services. Cryptocurrencies are deployed over public blockchains which have the transactions duplicated and dispersed across multiple nodes within a computer network. This decentralized mechanism is devised in order to achieve reliability in a network consisting of unreliable nodes. Privacy, anonymity and security have become crucial in this context. For that reason, formal and mathematical approaches are gaining popularity in order to guarantee the correctness of the cryptocurrency implementations. Mimblewimble is a privacy-oriented cryptocurrency technology which provides security and scalability properties that distinguish it from other protocols of its kind. Mimblewimble combines confidential transactions, CoinJoin and cut-through to achieve a higher level of privacy and security, as well as, scalability. In this work, we present and discuss these security properties and outline the basis of a model-driven verification approach to address the certification of the correctness of the protocol implementations. In particular, we propose an idealized model that is key in the described verification process. Then, we identify and precisely state the conditions for our model to ensure the verification of relevant security properties of Mimblewimble. In addition, we analyze the Grin and Beam implementations of Mimblewimble in their current state of development. We present detailed connections between our model and their implementations regarding the Mimblewimble structure and its security properties. Finally, we analyze the Litecoin soft-fork that enhances privacy over the blockchain based on Mimblewimble features.