Cyril Grunspan, Ricardo Perez-Marco
On profitability of selfish mining
(58K, LaTex)

ABSTRACT.  We review the so called selfish mining strategy in the Bitcoin network and properly evaluate the cost of the attack and its profitability. The expected duration of the attack has been ignored in the literature but is critical. We prove that such strategy can only be profitable after a difficulty adjustment. Therefore, it is an attack on the difficulty adjustment algorithm. We propose an improvement of Bitcoin protocol making it inmune to a selfish mining attack.