Looking for an N -out-of-M split algorithm

[Wang, Steve]

For large files, you might also want to take a look of the following
paper

Krawczyk, H. Secret sharing made short. In Advances in Cryptology --
Crypto '93. pages 136-146

See also HAC pages 539.

Steve

-----Original Message-----
From: owner-cryptography at metzdowd.com
[mailto:owner-cryptography at metzdowd.com] On Behalf Of
Jill.Ramonsky at Aculab.com
Sent: Wednesday, July 16, 2003 11:59 AM
To: cryptography at metzdowd.com
Subject: Looking for an N -out-of-M split algorithm

Hi,
 
I remember reading (many years ago) a description on some web page
somewhere
of an algorithm by which an arbitrary file F could be split into M
pieces,
such that:
(1) given any N pieces, F can be reconstructed precisely, and
(2) given fewer than N pieces, it is impossible to determine even a
single
bit of information about F.
 
Unfortunately, that was many years ago, and -- search as I might -- I
haven't been able to find it on web now.
 
Does anyone have any idea where I might learn about this algorithm - or
indeed any algorithm which does the job.
 
Jill

[Moderator's note: look for "Shamir Sharing" -- the trick is just
turning the secret into a polynomial of degree N so that with enough
points you determine the polynomial uniquely and with too few you
can't determine it. I'm pretty sure that Schneier and all of the other
standard references explain this trick. --Perry]
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