time-stamp server uses (Re: Question on U.S. Postal Service and crypto)

[Adam Back <aba@dcs.ex.ac.uk>]

Robert Costner <pooh@efga.org> writes:
> [...]  The timestamping is a action that "postmarks" the digitally
> signed message.  Many attorneys feel this is a very good thing,
> though I have had a hard time justifying the need for this to some
> technically inclined people.

One use for time-stamping is to allow digital signatures to out-live
the validity period of a given public private key pair.  If the
time-stamped signature shows that the document was signed during the
life-time of the signing key pair this provides additional assurance
that the signature is still valid despite the fact that the key is now
marked as expired, or was say later compromised and revoked.

Lots of other uses for time-stamping services also; I thought of a use
for them in the eternity service in preventing race conditions.

Adam
-- 
Now officially an EAR violation...
Have *you* exported RSA today? --> http://www.dcs.ex.ac.uk/~aba/rsa/

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)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`