Shell's authentication needs

[L. McCarthy]

Rich Salz writes:
> Shell needs public key because they want to use email for legal contracts.
> They've been waiting for standards to come around, but have given up.
> They're currently planning on using NIST's DSS, if they can fix a few things:
>     -	Add concepts of time and location (it can be important to prove
> 	that this was signed last month outside of the U.S.)

Any thoughts on how digital "place-stamping" (analogous to timestamping) might
be accomplished, to authenticate the location of origin of a document ?

 -L. McCarthy / seeking a summer job/internship; BS CS Cornell & 2 years'
  grad work in theoretical CS (algebraic algorithms); private email for info