Chaffing & winnowing without overhead

[Jesús Cea Avión]

You can have chaffing & winnowing without bandwidth overhead, but the
resulting scheme hasn't the original "elegance" anymore. In particular,
you don't send the plaintext on the clear.

The new schema is useful to cypher a document using any standard
signature library, exportable by definition. Very nice :), since you can
use, at last, strong crypto :).

a) When the connection starts, negociate an initial sequence number.
   The sequence number mustn't be reused. We assume a ordered delivery,
   like TCP.

b) Calculate the signature for:

   [sequence]0  ->  MAC0
   
   and

   [sequence]1  ->  MAC1

c) Compare both MACs and locate the first "different" bit,
   from high to low bit or viceversa.

d) Send that bit from MAC0 if you want to send a "0" or from
   MAC1 if you want to send a "1".

-- 
Jesus Cea Avion                         _/_/      _/_/_/        _/_/_/
jcea at argo.es http://www.argo.es/~jcea/ _/_/    _/_/  _/_/    _/_/  _/_/
                                      _/_/    _/_/          _/_/_/_/_/
PGP Key Available at KeyServ   _/_/  _/_/    _/_/          _/_/  _/_/
"Things are not so easy"      _/_/  _/_/    _/_/  _/_/    _/_/  _/_/
"My name is Dump, Core Dump"   _/_/_/        _/_/_/      _/_/  _/_/
"El amor es poner tu felicidad en la felicidad de otro" - Leibnitz