Re: Rivest's Chaffing and Winnowing

TM (messiah@jps.net)
Sun, 22 Mar 1998 18:41:24 -0800

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An implementation for Windows 95/NT4 of Rivest's "chaffing" idea can be
found at
http://www.sinnerz.com/tmessiah/cnw.zip

All it does is chaffs or winnows a file. Data file size to chaff file size
ratio is 1:24*PacketNumber, where PacketNumber is a user-defined number
between 1 and 6.

It needs a better PRNG or RNG to create chaff packets, and to merge the
chaff packets with the wheat packets. (What an odd metaphor for data.)

Instead of using HMAC-SHA or another large-digest MAC, I simply used 32-bit
CRCs to save space and time. The MAC of byte M is CRC(M+Password+M), where
"+" denotes concatenation.

Each packet consists of a 32-bit serial number, one byte of data, and a
32-bit MAC.

It doesn't check the serial numbers of the packets, but that could be
implemented easily.

It's in the public domain, so have fun. I know, this is really a waste of
time, because it's not meant for storage encryption, but for communication,
but I thought it was a neat little twist on traditional encryption methods,
and felt like giving it a little nudge down the road to maturity or
something. Hell, I felt like programming. =o)

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Version: PGPfreeware 5.5.3 for non-commercial use <http://www.pgp.com>
Comment: KeyID: 0x14C4FDE6, DH/DSS Public Key

iQA/AwUBNRXL0wdZfH4UxP3mEQK6BACfR9U0dd37NsaU5jA+mBv9dQU2iNQAoMVL
a6NqVM1A40omm0BoZMD+Sh2Q
=2+pb
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"I never set out to be weird. It was always the other people
 who called me weird."
-- Frank Zappa --

http://www.sinnerz.com/tmessiah/
KeyID: 4096/1024/0x14C4FDE6
Fingerprint: 1263 DBFD F2C4 77C6 87F2 A94A 0759 7C7E 14C4 FDE6

     -export-a-crypto-system-sig -RSA-3-lines-PERL
#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj
$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1
lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)

• Next message: Perry E. Metzger: "Re: What are the DC instuctions buried in RSA in 3 lines of perl?"
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• Reply: Ge' Weijers: "Re: Rivest's Chaffing and Winnowing"