Our prediction for the winner of the
2002 Super Bowl is:
The final two teams will be New England
and St. Louis.
New England will win 20-17 with a last-
minute field goal.
Amazing prediction, eh? That’s because we wrote it after the game…. even though
signed_demo.doc was timestamped a few weeks before the game, and its contents
haven’t changed…
That’s because the original signed_demo.doc contained a Macro that, upon opening (but
after signature verification) replaced all of its contents with:
http://www.cs.dartmouth.edu/~pkilab/demos/workflow/spoof_demo.doc
Each time we change the document at the above URL, we change what you see when you
open the signed document---without changing the binary of the signed document, or its
signature.
To demonstrate this in a fun way, we put a remarkably accurate prediction of the Super
Bowl here (after the game is played). When you open signed_demo.doc---signed and
timestamped before the game---you’ll see this accurate prediction.
For more information, see
http://www.cs.dartmouth.edu/~pkilab/demos/workflow/