splitting keys

Adrian 'Dagurashibanipal' von Bidder avbidder@fortytwo.ch
Sat Mar 1 11:00:01 2003

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[no cc:s necessary. Thanks.]

On Sat, 2003-03-01 at 05:09, Michael H. Warfield wrote:

> 	There is a neat trick with RSA where you can distribute the
> secret key between many computers and never need to reassemble them.
> You give them all the same modulus (pq result) but you split the secret
> exponent between them such that the sum of the exponent adds up to your
> secret exponent.

Funnily enough, I had an exam yesterday morning, and EXACTLY THIS was
one of the exam questions...

Ok, this thing with the RSA exponent works fine.

The beautiful thing with the classical 'secret sharing' algorithms is
that you can do things like 'any 3 out of 5 may sign a document'. I have
not thought about it - with calculating in finite groups, it could be
possible to do it. In any case: yes, it was such things that I was
thinking about.

-- vbi

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