Comment by zzo38computer

How I had idea of a computer and operating system design, measuring time also requires a capability. Creating files (including temporary files) also requires capabilities. Shared memory is read-only by everyone; to be able to write to memory you must have exclusive access. All of these capabilities are not necessarily what the program using them intended them to be; they may also be proxies, or capabilities of the wrong type (the kernel does not know anything about the types of capabilities except those it created itself), etc. A proxy may limit communication from one program to a service. Using these as well as other things (including, but not limited to, the CPU design), there are things that can be done to mitigate these problems (including things necessary to mitigate other kind of timing attacks based on other capabilities, e.g. slowing down network access for purpose of testing its working on slow networks).