Re: applying AES-GCM to secure shell: proposed "tweak"

[Joseph Galbraith <galb-list%vandyke.com@localhost>]

Peter Gutmann wrote:
> Nicolas Williams <Nicolas.Williams%sun.com@localhost> writes:
>
>   
> > Er, actually, I'm not sure.  It depends on what implementations do with it
> > now when it's not set to 0.  Hmmm, what does the spec say to do about that
> > field?  Sadly: nothing, at least not in section 7.1.
> >     
>
> Well if it's RFU then it's implied that you ignore it, which has been the 
> practice for RFU fields since at least the 1970s (in things like status flags 
> registers), and probably even earlier but I wasn't playing with computer 
> hardware back then.
>
> How about a quick straw poll, since we've probably got a good number of
> implemeters here.  If your implementation sees a non-zero value in the RFU
> field, will it:
>
>   1. Ignore it and continue, since it's RFU.
>   2. Run Nethack, and failing that, emacs in Towers-of-Hanoi mode.
>   3. Reformat the hard drive.
>   4. ???
>   5. Profit.
>
> Peter.
>   

And as for our implementation, it will ASSERT() for debug
builds (which we don't ship so it isn't a big deal) and
ignore the value in release builds.

Thanks,

Joseph