Playing card cryptosystems

[paul at fatmans.demon.co.uk]

> Also I did hear tell that Bruce Schneier was working on a crypto
> algorithm which was designed to work with playing cards, for a book
> which Neal Stephenson is writing.  Presumably painful to use, but
> maybe good plausible deniability, all that you need is a pack of
> cards.

Not even that in fact, there are methods, and I can confirm they work 
because I can do it myself, that allow one to memorize the order of a 
pack of playing cards, some people can even do it with up to 8 packs, 
although this requires a more complicated method. So while encryption 
requires one to have the cards ready (about 8 good riffle shuffles 
will restore a high degree of randomness to a deck) you can keep the 
pad for short messages in your head. But one can do the same with one 
time pads that use other plaintexts as the pad.

 

  Datacomms Technologies web authoring and data security
       Paul Bradley, Paul at fatmans.demon.co.uk
  Paul at crypto.uk.eu.org, Paul at cryptography.uk.eu.org    
       Http://www.cryptography.home.ml.org/
      Email for PGP public key, ID: 5BBFAEB1
     "Don`t forget to mount a scratch monkey"