Re: your mail

lilley (lilley@afs.mcc.ac.uk)
Tue, 4 Apr 1995 16:16:34 +0500


Jon wrote:
> Robert Robbins <rrobbins@gdb.org> wrote:
> | On Mon, 3 Apr 1995, Dan Connolly wrote:
> |
> | > The right answer is digitally signed distributions. Then only can
> | > you be certain that the bits have not changed since they left
> | > the author's hands.

> | Doesn't this suggest some utility in extending the URN/URL concept to
> | include an optional computed checksum as part of the identifier? Verifying
> | perfect identity of what you are getting against what you thought you were
> | requesting has some value for materials other than programs, too.

Yes. In particular, it requires the MD attribute on all A and IMG tags, anything
thay takes a URI as an attrribute.

> | The checksum could be recomputed dynamically every time the file is
> | transferred (as checksums are now computed dynamically every time an IP
> | packet is placed on or taken from a communication medium).

> My initial reaction is it makes more sense for a new document type:
> signed-html.
> The viewers for signed-html then worry about authentuicating the signature and
> displaying proper messages etc.

That is another level of security, where the document can be updated by
the original author, signed again, and the link is still valid. MD checksums
will not cope with that, as you say.

> I dont think a checksum is part of either a name (URN) or a location (URL).

But it is part of a link, in HTML 3.0; this does not require any changes
to the URI syntax.

--
Chris Lilley
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