Risk of Asynchronous Protocol Update: Attacks to Monero Protocols

In a cryptocurrency system, the protocol incorporated in the node application runs without human intervention. Cryptographic techniques are implemented to determine the ownership of the coins; they enable the owners to transfer the ownership of the coins to other users. Consensus protocols are employed to determine the source of the truth of the information contained in the public ledger called blockchain. When the protocol needs to be updated, all nodes need to replace the application with the newest release. We explore an event where an asynchronous protocol update opens a vulnerability in Monero nodes which have not yet updated to the newest software version. We show that a Denial of Service attack can be launched against the nodes running the outdated protocol, where the attack significantly reduces the system’ performance. We also show that an attacker, given a sufficient access to cryptocurrency services, is able to utilise the Denial of Service attack to launch a traceability attack.