Comment by AlotOfReading

The hash comparison can still be susceptible to timing attacks. Here's a historical example that affected Java: https://codahale.com/a-lesson-in-timing-attacks/

I was really hoping this post would include a demonstration of type-level safety against such attacks given the mention in the intro. It's not obvious to me how the demo would be extended to cover such timing leaks. I suspect that even with type-level safety, you're still at the mercy of the optimizer and language runtime to maintain those security properties. Can you specify constant time codegen or other constraints with GHC?