They are reverse engineered. Paper money has a limited downside. In the US, we know there aren't bills over $100 in general circulation, so you can, with effort

They are reverse engineered. Paper money has a limited downside. In the US, we know there aren't bills over $100 in general circulation, so you can, with effort, print up a few million dollars. The money supply of paper-ish money (M1) is around 3.4 trillion dollars. From the point of view of the principal actor US mint this is annoying and needs to be dealt with, but it's not a danger to the system unless it is allowed to run unchecked. The power imbalance involved is what makes it work. For crypto, the principal actor is whoever is encrypting. The downside of an activist in a repressive regime having their crypto broken is basically unlimited for them. Or the population that uses ecommerce as principal actor. The downside for them is enormous and the upside for someone who suborns a system incredible. Since we don't know tye power and incentive imbalance between the actors, crypto has to assume the worst.