Is the context of "constant time" algorithms inclusive when you have a clock control?
When I read a paper that specifically says that it robust to side channel attacks because the algorithm is constant time, is the assumption that one does not have clock/voltage control?


Generally, when we mention side channel without context, we actually mean a side channel in software. I.e. an adversary has (only) the ability to run code on the same CPU. Moreover, the adversary does not have physical access to the executing CPU.

In your case—underclocking the CPU and screwing around with the power supply—you are manipulating the CPU itself. In my book this would be considered a fault attack, which is a technique in hardware side channel analysis. Hardware side channel analysis is super-powerful, and because so much is possible it has a less obvious defined attacker model.

So it kinda depends on the context. Most of the time the literature will be about software side channels (time, cache, etc.). But when you are reading a CHES paper, it's probably about hardware.