[RFC v2 00/13] Multi-Key Total Memory Encryption API (MKTME)

[Sakkinen, Jarkko]

On Fri, 2018-12-07 at 13:59 -0800, Jarkko Sakkinen wrote:
> On Fri, 2018-12-07 at 14:57 +0300, Kirill A. Shutemov wrote:
> > > What is the threat model anyway for AMD and Intel technologies?
> > > 
> > > For me it looks like that you can read, write and even replay 
> > > encrypted pages both in SME and TME. 
> > 
> > What replay attack are you talking about? MKTME uses AES-XTS with physical
> > address tweak. So the data is tied to the place in physical address space
> > and
> > replacing one encrypted page with another encrypted page from different
> > address will produce garbage on decryption.
> 
> Just trying to understand how this works.
> 
> So you use physical address like a nonce/version for the page and
> thus prevent replay? Was not aware of this.

The brutal fact is that a physical address is an astronomical stretch
from a random value or increasing counter. Thus, it is fair to say that
MKTME provides only naive measures against replay attacks...

/Jarkko