On The Unforkability of Monero

Monero, ranked as one of the top privacy-preserving cryptocurrencies by market cap, introduced semi-annual hard fork in 2018. Although hard fork is not an uncommon event in the cryptocurrency industry, the two hard forks in 2018 caused an anonymity risk to Monero where transactions became traceable due to the problem of key reuse. Thisproblem was triggered by the existence of multiple copies of the same coin on different Monero blockchain branches such that the users spent the coins multiple times without preemptive action. We investigate the Monero hard fork events by analysing the transaction data on three different branches of the Monero blockchain. Although we have discovered an insignificant portion of traceable inputs compared to the total available inputs in our dataset, our analyses show that the scalability of the event depends on external factors such as market price and market availability. We propose a cheap, easy to implement strategy to prevent the problem of key reuse, should in the future stronger Monero forks emerge in the market.