Howard Chu (hyc.delete@this.symas.com) on December 11, 2018 4:17 am wrote:
>
> Will definitely be interesting to follow this issue going forward. It looks like
> MRAM is poised to replace SRAM for on-chip caches, down the road. Encrypting cache
> contents would quite impractical.
>
> http://www.eenewsanalog.com//news/mram-beats-sram-close-logic-caches
>
> https://www.eejournal.com/article/an-mram-cell-that-competes-with-sram/



Yes indeed, encrypting cache contents does not seem an acceptable solution.


Nevertheless, encryption is probably not needed in this case.


Unlike for external DIMMs, you cannot remove the caches from the system and examine them separately and there is no need for the caches to be persistent.


If the CPU will always automatically clear the caches during power-up and during power-down, that should be enough.


To work around that, you should be able to remove the supply voltage instantly from the processor while it was in use by its owner, than to decapsulate it and use some very expensive tool to determine the states of the bits in the caches.


Even if this is not completely impossible, it is outside the range of abilities of a normal thief.

If someone that could do that would be interested in your cache content, then you would be a surveillance target and you should fear other much simpler methods of watching what you do.