howto secure older keys after the recent attacks

Robert J. Hansen rjh at
Sun Sep 13 04:18:59 CEST 2009

Faramir wrote:
> I remember an example from one of the Bruce Schneier book, where 2
> people (Alice and Bob, of course) wanted to get a random bit. They
> thought about each one flipping a coin, and then mixing the results.

[puts on his voting security hat]

This is part of some voting protocols.  Let's say you have two
candidates who tie in an election.  Each candidate sends their own
representative to the election with a ten-sided die (you can find these
in any hobby store).  The election commissioner collects the dice, then
distributes them out randomly to the representatives.  Everyone throws
the dice and the numbers are added up together modulo 10.  If it comes
up 0 through 4, candidate A wins the election; if it comes up 5 through
9, candidate B wins the election.  Thanks to the magic of random
distributions and modulo math, as long as there's one fair die in the
system, the entire system is fair.

Anyway.  This is apropos of nothing except to show you that such schemes
really are used in the real world.  :)

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