There is another problem, because the clock of a modern computer can be set to any given time, there is no purely cryptographic way to be satisfied that a given document existed at a given time, if you do not trust the computer (and the person controling it) generating the timestamp. There is a third party solution to this problem exiting on the internet. The "PGP Digital Timestamping Service" at http://www.itconsult.co.uk/stamper.htm In the general case, there is no reason to mistrust this third party, since the service is automated, and does not have time to scan your timestamp requests to participate in order to comspire against you. In addition, summaries of timestamp requests are posted to usenet newgroups, where they are presumably archived at many archiving sites. Thus if you do carefull checking, the only way timestamp fraud could work would be if this site, together with all the usenet archiving sites that you checked, were engaged in a conspiracy against you. Hopefully, you will think the probablility of this is small. -- Paul Elliott 1(512)837-9345 1(512)837-1096PGP Digital Timestamping Service pelliott@io.com PMB 181, 11900 Metric Blvd Suite J http://www.io.com/~pelliott/pme/ Austin TX 78758-3117