Cryptography and evil

I was going to write a blog post about mathematical cryptography problems, like good hash algorithms, getting padding right and other juicy problems and contrasting them to social cryptography problems, like trusting keys and blockchain forking. Then I came across this page on Ethereum problems:

While before cryptography was, by and large, a purely computational and information-theoretic science, with strong guarantees built on security assumptions that are close to absolute, once money enters the picture the perfect world of mathematics must interact with a much more messy reality of human social structures, economic incentives, partial guarantees and known vulnerabilities that can only be mitigated, and not outright removed.

That says it better than I could. However I would also have said one of the underlying problems is evil, such as manifested in a 51% attack (that's about one specific attack, but it applies to cryptocurrency generally). Lots of interesting problems to solve!