Problem with faked-system-time option

Jerome Baum jerome at
Thu Jun 16 02:30:37 CEST 2011

> The parties themselves could nest signatures on a document: A signs, B
> signs the signed document, A signs again, B signs again. Each party
> has a signature that is constrained to have been applied between two
> signatures of the other party. Would that not remove the need for a
> timestamping service?

Sounds interesting. Assuming the court will understand the second
signature to mean "I confirm that the timestamp of the other party's
signature is correct", then in your scenario A and B are both unable
to repudiate the inner timestamps. Doesn't stop a third party from
disputing the accuracy of the timestamps though, as A and B may have
shared interests in inaccurate timestamps (picture back-dating an
invoice/contract for tax fraud).

>> Timestamp authorities are *trusted* to be fair and
>> honest -- but that's not the same thing as *proven* to
>> be, and nothing in the world is easier to revoke than
>> trust.
> Even those that publish records/hashes are not really *proving* their
> integrity.

Right. The service isn't trusted, the published signatures are (and
only w.r.t. time interval/week and possibly order, depending on

Jerome Baum
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email jerome at
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