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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:16:18 ADT
Jim Gillogly (jim@mentat.com)
Thu, 26 Mar 98 17:44:58 PST
Ron Rivest writes:
> the revised version of my "chaffing and winnowing" paper
> http://theory.lcs.mit.edu/~rivest/chaffing.txt
> contains a more efficient implmentation, in the sense that you can
> have packets with large amounts of information per packet...
This package transform stuff is nice.
It also means you don't have to have matched chaff packets for each
wheat packet. For example, if you want to make the work factor 2^90,
you can send 90 packets of matched chaff and wheat, and send the rest
of the packaged wheat packets naked; even without authentication if you
wish. The attacker needs to try both of each pair of matched pkts.
For large messages, the efficiency of transmission appears to approach
a factor of 1 instead of a factor of 2 overhead. (Or a factor of 200
with the original 1 bit per packet method.)
And, as Rivest points out in his "All-Or-Nothing Encryption and the
Package Transform" paper (also on his website), the work factor must
include the cost of the attacker unpackaging the whole message 2^N
times, so that with large messages you don't need as many as 90
matched pairs to get the equivalent of 2^90 protection.
Jim Gillogly
"Oh, winnow all my folly, folly, folly and you'll find
A grain or two of truth among the chaff."
W.S. Gilbert, "Yeomen of the Guard"
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:16:18 ADT