The only solution to this sort of attack is to have the keys always in encrypted form
in-memory.`Then when the system needs to have the key it can be decrypted and accessed quickly
in CPU cache.
The sort of memory used in CPU cache is different then the sort that is used in main system
memory. So hopefull that cpu cache, besides being much faster, does not have the same
properties of regular Dram.
Or maybe have a built-in hardware tripwire that would 'zap' the ram in case of sudden power
loss. Nothing that would destroy the ram, but enough to flip all the bits back to zero or
something like that.
I expect that the only total solution would be change the design of the hardware like that.
Hopefully something that could be built-into the ram so that you would not have to modify the
design of the motherboard.