As long as the cost of the attack is affordable by states, states can launch the attack. Always remember cryptocurrency is much more an economic issue than a computer science issue and the overall attack vectors are far more than the vectors from computer science; a computer science expert says that Joe's email password is strong enough to break in 1000 years but then Joe always fails in the attack in a social way by phishing or bribe.
Hashing Power Attack
One needs to purchase sufficient mining rigs to launch this attack. The cost of this attack can be estimated by:
The cost is
Nodes Seize Attack
One needs to conduct inspection for possible nodes among the internet and seize them. The cost of this attack can be estimated by:
Assume exponential distribution for computer's internet speed. This is the maximum entropy distribution with knowledge of positiveness and average mean. With the weakest assumption, it is more conservative compared with a Pareto distribution assumption; see here for the difference between the exponential distribution and typical Pareto distributions.
When states have no idea where the nodes are, the number of potential nodes in eyes of states detectives is so the total cost of the attack is
This also settles the block size dispute for solid number because of its relation with a proper internet speed. The logic goes like this:
We can do no more better because of the First Law of Cryptocurrency. With this B, only transactions with fee greater than f is feasible. We feel blessed if our preferred transactions are covered. We feel compromised if our preferred transactions are not covered; don't curse anyone if we can not use this cryptocurrency for coffee.