In response to the GPG.Fail attacks, a Hacker News user made this claim about the 64-bit "Long Key IDs" used by OpenPGP and GnuPG, while responding to an answer I gave to someone else's question: OK, to be clear, I am specifically contending that a key fingerprint does not include collisions. My proof is empirical, that no…

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A practical demonstration of a collision attack against PGP's 64-bit Long Key IDs, achieved in 3 days on a laptop using birthday attack principles. Two different PGP keypairs were generated that share the same Long Key ID (948F9326DD647C78), exploiting the mathematical reality that 64-bit outputs require only ~2^32 attempts for 50% collision probability. The attack methodology involved generating keypairs, iterating timestamps, computing Key IDs, sorting results, and identifying collisions. Complete proof-of-concept code and both public and private keys are provided, demonstrating that empirical security claims about 64-bit identifiers are fundamentally flawed.

Practical Collision Attack Against Long Key IDs in PGP