From: Breathnach, Proinnsias (Dublin) (breatpro at domain exchange.ie.ml.com)
Date: Tue 22 May 2001 - 16:19:39 IST
That method would work for small numbers ... n < 5 for example ... but over
that you have problems ...
For 3 people you need three keys, everyone has two of those so:
Person - Keys
1 - A,B
2 - B,C
3 - C,A
Ensuring that any pair can decrypt the message (encrypted with 3 keys)
For 4 people it becomes
Person - Keys
1 - A,B,C
2 - B,C,D
3 - C,D,A
4 - D,A,B
Again the only combination ensuring that any pair can open the message (this
time encrypted with 4 keys)
As far as I know that's about the only way this could work completely ...
> -----Original Message-----
> > At any point you want to make sure that any *two* of those people can
> unlock a private key to decrypt those files.
> If you could split the group in two, you could create an 'A' key and a
> 'B' key, double-encrypt the secret documents with both, then
> distribute the 'A' key to each member of the 'A' group, and similarly
> give the 'B' group copies of the 'B' key. This means whoever's
> producing the documents only needs to encrypt twice, but it does mean
> that if the 'A' group are wiped out, the 'B' group cannot access the
> blueprints to the doomsday device (or whatever).
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