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Long Range Attack

Definition

A long range attack is a sophisticated form of attack against Proof-of-Stake blockchains where an attacker attempts to rewrite a significant portion of the chain’s history from an early point. This is achieved by compromising old private keys of validators who are no longer active on the chain. The attacker then uses these keys to forge an alternative, longer chain that originates from a point far back in time. Such an attack exploits the fact that old stakes are no longer economically active, making it potentially cheaper to acquire historical validator keys.