Time to move the source code and the signing key to Germany.
Signing keys don't have to be kept in just one country. Secret-sharing schemes allow you to "split" them up into as many pieces as you like, which can all be stored in different countries, either requiring them all to agree to make a signature, or requiring a certain number of them to agree. Having an insufficient number of pieces is no better than having none at all.
It's exceptionally easy to determine the factors of any large prime number because there are only two; the number one the number itself.
But you don't know that it's prime until you've discovered its factors... (Specifically, that they don't include anything other than itself.)
And proving that a large prime number is in fact prime is actually quite hard. Fortunately, it's not too difficult to very nearly prove it. What actually happens in real-world large-prime crypto is that you run enough statistical tests on the number that the probability of it not being prime becomes lower than the probability of someone just guessing the key with pure luck, or is otherwise not the weakest link in the chain.
The problem here is... just viewing the picture is creating a 'demand' for such material, and therefore a supply must be created, which exploits minors. I'm not really on board with the drawings of such things being forbidden as well, that seems like overkill to me, and drawings may supply the consumers of such materials that aren't exploitative of minors. It's an ugly nasty situation for sure.
Not necessarily. Certainly if someone's paying for it, they're going to incentivise production. But at the other end, there's the situation where someone's downloading it off a server which isn't counting the number of downloads or isn't telling the provider, which is often going to be the case when, for example, it gets spammed onto third-party imageboards, in which case people viewing it aren't affecting the outside world in any way.
And consider. So downloading child porn off P2P services, which is a way of viewing such material, that increases the incentives to make it? Well, downloading copyrighted material off P2P services reduces the incentives to make it, as the copyright lobby loves telling us. These two things don't sound very consistent.
As Slashdot loves noticing, the normal rules of supply and demand don't apply to information when you have this almost infinitely efficient machine for copying it called the internet.
1 Sagan = Billions & Billions