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At 20:12 +0930 on 09/15/2006, Alphax wrote about Using an "N out of M keys"
system:
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I've heard it mentioned before that some versions of PGP (probably the
8.x and 9.x families) have a system where a message can be decrypted by
any n out of m keys used in conjunction. Is this true, and how is it
implemented? One rather cumbersome method that I can think of is
(working backwards):
- - - Any of the M keys can decrypt the first of N layers
- - - Any other key can decrypt the next layer
- - - ...
- - - Any key not used yet can decrypt the next layer
- - - ...
Is this anywhere even close, or does it (or would it) use a completely
different system?
- - --
Alphax
Death to <>tegorical imperative!
OpenPGP key: <http://tinyurl.com/lvq4g>http://tinyurl.com/lvq4g
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The way it works is the key is split into M parts in such a way that so
long as you have N of the parts it can be reconstructed. The reconstructed
key is the original key and is used as normal. To use a simplistic example
lets say the original key is:
ABC
and it is split into 3 parts:
X = 13AC (Where 13 means it has the 1st and 3rd piece)
Y = 12AB
Z = 23BC
Thus from any two you can recreate the original ABC.
The system is a LITTLE <g> more complex than this but basically works the
same way (ie: The data is distributed in such a way that each piece occurs
at least once so long as you have access to N parts and you can tell how
to recombine them).
- --
Robert A. Rosenberg
RAR Programming Systems Ltd.
(646)-349-4025 - Fax
(646)-479-1984 - Cell Phone
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