Re: Comments on draft-ietf-openpgp-rfc2440bis-12

[David Shaw <dshaw@xxxxxxxxxxxxxxx>]

On Sun, Jan 16, 2005 at 08:03:54AM +0000, Ben Laurie wrote:
> 
> David Shaw wrote:
> >On Sat, Jan 15, 2005 at 04:38:32PM -0500, David Shaw wrote:
> >
> >>On Sat, Jan 15, 2005 at 08:54:51PM +0000, Ben Laurie wrote:
> >>
> >>>3.2 (MPI) doesn't specify what the unused bits should be set to. This 
> >>>may be deliberate but I think it should either say they MUST be zero 
> >>>(which I prefer) or that their content is unspecified.
> >>
> >>I'm not completely sure what you are referring to here.  Do you mean
> >>the difference (given an MPI of value "1") between [00 01 01] and [00
> >>01 02] ?  The 0x02 bit of the 3rd octet?
> >
> >
> >Er, I meant [00 01 03], but the question still holds.  Are you
> >referring to the 0x02 bit of the last octet?
> 
> Yes.

I see.  I think that the draft does indirectly specify that the unused
bits are 0.  In section 3.2 it states "These octets form a big-endian
number; a big-endian number can be made into an MPI by prefixing it
with the appropriate length."  [00 01 03] would violate that
statement, since the big-endian number would be 3, rather than 1.

I certainly don't have any objection to making it more explicit than
that, though.

David