  Proof-of-Work mining is intended to provide blockchains with robustness
against double-spend attacks. However, an economic analysis that follows from
Budish (2018), which considers free entry conditions together with the ability
to rent sufficient hashrate to conduct an attack, suggests that the resulting
block rewards can make an attack cheap. We formalize a defense to double-spend
attacks. We show that when the victim can counterattack in the same way as the
attacker, this leads to a variation on the classic game-theoretic War of
Attrition model. The threat of this kind of counterattack induces a subgame
perfect equilibrium in which no attack occurs in the first place.

Cryptography and Security;Computer Science and Game Theory