You have to ensure the attacker can't measure temperature-induced clock drift, because you can still measure the amount of work the CPU is doing to surprising a

You have to ensure the attacker can't measure temperature-induced clock drift, because you can still measure the amount of work the CPU is doing to surprising accuracy. You can probably introduce extra busy-work, or farm the work out to satellite servers whose timing jitter can't be observed at the microsecond level. You can also run your lookup against uncacheable memory, so that the attacker can't detect hot keys. There's still some memory timing analysis available because of DRAM banking, though. Security is a process :-)