@ianthetechie @kytta I believe this falls under "verifiable computing". Blockchain has some solutions for this (for eg: the code for a smart contract is executed on every node with fully deterministic results) but of course, it's not feasible economically for most of the real-world applications.

Of course, at extreme, you can't even trust that a program on your own machine does what its source says it does. A classic paper is "Trusting Trust" by Ken Thompson: https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_ReflectionsonTrustingTrust.pdf