With all of the discussion of C&W, and potential expansion, along with a sideband discussion of same, I decided to ask 'the man' himself. The '10K email file' used in the example came from the sideband discussion. Forwarded for your edification. ------- Start of forwarded message ------- Date: Tue, 12 May 1998 18:24:46 -0400 From: Ron Rivest <rivest@theory.lcs.mit.edu> Subject: Chaffing question Suppose you can start with a 10KB email file. Running a package (all-or-nothing) transform on it adds only a small amount to the length---say 128 bits total, or less (basically the length of a key in your favorite algorithm). You can break the result into 128 one-bit blocks and one 10KB block. MAC each block. Add 128 bits of chaff, intermingled with the first 128 blocks from above. The final result has 128+128+1 packets, and total length 10KB (the original email) + 257*64 bits (for the 257 64-bit MAC values) plus 128 bits (the chaff bits), and assuming that the sequence numbers are implicit rather than explicit, you get a total of around 12.3 KB. Cheers, Ron ------- End of forwarded message ------- -- Jim Thompson / Smallworks, Inc. / jim@smallworks.com 512 338 0619 phone / 512 338 0625 fax Real, cheap Hardware RNG: http://www.fringeware.com/nscd/