LYNX-DEV stealth encryption

[Philip Webb]

[ i'm not going to make a habit of posting news articles on lynx-dev,
but there do happen to be  2  today which should be of interest ]

Making sense of absolute nonsense -- Kurt Kleiner -- New Scientist 980402
                                      
A new technique for sending secret messages over the Internet could undermine
the US government's attempts to limit the spread of communication methods
that can't be deciphered by its security forces.  Ronald Rivest, computer
scientist (MIT), has posted a paper on the Internet describing `chaffing
& winnowing', which exploits digital authentication to hide content.
   
US Federal officials have endorsed authentication, in which people send
a digital signature with a document to prove it is from them.  To create
a signature, a key known only to the sender is combined with data
in the document to produce a unique value; anyone who has been given
a related key can use it to authenticate the signature, but not reproduce it.

In Rivest's method, no part of the message is actually encrypted.  Instead,
it is split into tiny pieces, each of which is labelled with a number
& digitally signed.  The message is then interspersed with nonsense data
that are also numbered & appear to be signed, but not with the sender's
true signature.  Anyone with the correct authentication key can separate
-- winnow -- the `wheat' of the message from the `chaff', but no one else
can put the pieces together.
   
Chaffing & winnowing is less efficient than conventional encryption,
because it increases the size of the message, but it should be effective
& makes nonsense of the US ban on exporting strong encryption: "This shows
some of the built-in absurdities of export control", says Michael Froomkin
(U Miami School of Law, Coral Gables FL).
   
  Ronald Rivest, "Chaffing & winnowing"
    --  theory.lcs.mit.edu/~rivest/chaffing.txt

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