[tor-talk] BitMail.sf.net v 0.6 - Secure Encrypting Email Client

[Robert J. Hansen]

On 11/17/2013 11:44 AM, dan at geer.org wrote:
> Well said.  Two binaries can be execution identical except for their
> use of registers -- their use of registers being an artefact of the
> compiler.

In fact, it goes even deeper than that: many architectures allow their
processor to dynamically reorganize and/or modify the code being
executed.  (Out-of-order execution is one example of this.)  So even if
you're running two binaries that are completely identical, the CPU may
process them quite differently depending on the state of the system.
This has some extraordinary implications for those who are trying to
guarantee their CPU is operating exactly the same as another CPU!

Every couple of years I look at this problem, read a couple of papers,
and walk away muttering about now is a great time to start drinking
heavily...