Re: Compression Order

I think the issue is not the size of the signatures (which may be small), but
the size of the document being signed, which may be enormous. Compressing the
document prior to signing it means less processing overhead when performing the
signature operation. (This is a benefit for compressing first.)

But I lean toward the Signing First approach. Another benefit of that is you can
uncompress it and make it readable and not violate the signature. If you
compress first, uncompressing it means you are no longer looking at a signed
document.

Kit Lueder.
MITRE.

joe mcverry wrote:
> Signatures tend to be small - don't they?
> Joe
> 
> > David Fischer wrote:
> >
> > We are beginning to implement the Compression Draft specification:
> >
> > http://www.ietf.org/internet-drafts/draft-ietf-ediint-compression-00.txt
> >
> > and an implementation decision has arisen.  When Compression is
> > applied in concert with Signatures, which should be applied first?
> >
> >     Compress + Sign    or
> >     Sign + Compress
> >
> >         and
> >
> >     Compress + Sign + Encrypt   or
> >     Sign + Compress + Encrypt
> >
> > Different companies have presented valid business cases for each
> > alternative.
> >
> > The advocates for Signing first desire the signature to be over
> > readable text (you know what you are signing -- which is why we never
> > Sign after Encrypting).
> >
> > The advocates for Compressing first desire performance improvements.
> > In this case, Compression is compared as just another encoding scheme
> > so it is really still plain text.
> >
> > Discussions thus far have resulted in a consensus that the
> > implementors should be able to apply these functions in either order
> > when sending.  When receiving, the implementations should be able to
> > process either case.
> >
> > We are looking for further discussions. . .
> >
> > Regards,
> >
> > David Fischer
> > Drummond Group.

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