International Association
for Cryptologic Research

Selfish mining (SM) attack (Eyal and Sirer, CACM ’13) endangered Proof-of-Work blockchains by allowing a rational mining pool with a hash power (&#945;) much less than 50% of the whole network to deviate from the honest mining algorithm and to steal from the fair shares of honest miners. Since then, the attack has been studied extensively in various settings, for understanding its interesting dynamics, optimizing it, and mitigating it. In this context, first, we propose generalized formulas for the calculation of revenue and profitability from SM-type attacks. Second, we propose two different SM-type attacks on the state-of-the-art mitigation algorithm “Freshness Preferred” (Heilman, FC ’14). Our Oracle mining attack works on the setting with forgeable timestamps (i.e., if timestamps are not generated by an authority) and our Bold mining attack works on the setting with both forgeable or unforgeable timestamps (i.e., even if an authority issues timestamps). Although the use of timestamps would be promising for selfish mining mitigation, the analyses of our attacks show that Freshness Preferred is quite vulnerable in the presence of rational miners, as any rational miner with &#945; >0 can directly benefit from our attacks. Third, we propose an SM mitigation algorithm Fortis with forgeable timestamps, which protects the honest miners’ shares against any attacker with &#945;<27.0% against all the known SM-type attacks.