In software, you can spec the behavior of your program. And then it is possible to code to that exact spec. It is also possible, with encryption and stuff, to write specs that are safe even when malicious parties have control over certain parts.
This is not to say that writing such specs is easy, nor that coding to an exact spec is easy. Heck, I would even doubt that it is possible to do either thing consistently. My point is, the challenge is a lot harder. But the tools available are a lot stronger.
Its not a lost cause just because the challenge is so much harder.