That's what you'd think. Read some advanced cryptography papers and you'll discover it's not quite that simple. There are the exotic hardness assumptions: are

That's what you'd think. Read some advanced cryptography papers and you'll discover it's not quite that simple. There are the exotic hardness assumptions: are those mathematical problems really hard to solve or not? They aren't classical, natural problems like discrete log. Then there are the odd threat models, e.g. plenty of algorithms out there claim to be proven secure in the honest-but-curious model. Although this threat model isn't entirely naive, in the real business world "honest but curious" adversaries do appear in the imaginations of business leaders at least, but most people assume the point of cryptography is to keep you secure against arbitrarily malicious adversaries.