Feasibility of a Non-Quantum BTC Network Attack

The last post argued that 51% attacks -- regardless of motivation -- perpetrated by a state actor using quantum computing is still a long way's off. But it remains to be considered if such a state actor using co-conspirators of an axis of evil could succeed with such an attack and do catastrophic harm to the US economy (and do so for less cost than the cost of an actual military attack).

The answer, yes, that is feasible, but highly unlikely and also not irreparable, since the forking mechanism of the BTC network could simply revert to the previous block history prior to the attack and proceed from there.

The fact that it takes two weeks for the difficulty adjustment to offset growing hash rates does appear to be a little slow. Two weeks may have been fine in the early days of Bitcoin, but with the pace a volume of current international transactions, that might not be a fast enough feedback response.