Re: Timestamping
Doug Hughes (Doug.Hughes@Eng.Auburn.EDU)
Fri, 26 Jan 1996 17:59:09 -0600
--
____________________________________________________________________________
Doug Hughes Engineering Network Services
System/Net Admin Auburn University
doug@eng.auburn.edu
Pro is to Con as progress is to congress
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>Date: Thu, 25 Jan 1996 09:28:21 -0600
>To: ids@uow.edu.au
>From: dun@ncsa.uiuc.edu (Chris Dunlap)
>Subject: Re: Timestamping
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>
>It was on 1/22/96 at 8:41 AM when Doug Hughes wrote:
>>The best way to do this is with digital signatures. If you include the
>>timestamp in the body of the message, and then sign the body of the message
>>there can be no doubt about the time (unless you have a weak key-length, or
>>your key has been compromised). PGP/PEM will do this.
>There can be no doubt. Use the largest key you can.
>
>How do you prove the timestamp in the body of the message is the
>correct time in the first place? Your system clock could have been
>set forward or back before your digital signature. The whole point
>behind using a timestamping service is that their clock is supposedly
>secure (and somewhere outside of your control).
>
Yeah, it depends on your intentions. If you want something that
proves that somebody else sent something by a particular time, then a
trusted third party is the only alternative. However, if you just want
something that additionally authenticates a post for yourself, this can
be useful. This way, if a signed posting (purportedly by you) shows up
on Usenet at some day at some time, and the timestamp is way off, it would
raise a flag, thereby preventing replay sorts of hacks. (somebody taking
your posting, and, for whatever reason, sending it someplace else at a later
date in time)
I think we're straying from IDS though, so I won't post anymore on the subje
to the list.