[Cryptography] On improving the performance of the classical Playfair cipher

Tom Mitchell mitch at niftyegg.com
Thu Apr 7 18:08:57 EDT 2016


On Wed, Apr 6, 2016 at 1:55 PM, mok-kong shen <mok-kong.shen at t-online.de>
wrote:

>
> The classical Playfair cipher and its variant "two square cipher"
> (employing two Playfair matrices, used in WWII) are obviously too weak
> to be practically used today.

...

> Cities" from Project Gutenberg and took out the alphabetical characters
>

The "obviously too weak" bit might be a bit harsh.
It is a shared key system so would be fine for two person
simple messaging where the traffic is limited and statistics
are also limited by a small sample size.
Improvements should be paper, terminal and JacaScript friendly.

The alphabet limitations would bother some users (me).  Extended
eight bit ASCII seems a necessary feature today but not to the
point that smart VT100 type attacks and html escape problems
are possible.

The weakness should keep the big boys from bothering you
even if bolted into an App or js.browser plugin.

All systems have key management and usability issues.
As a "scramble()" block of code to build a better looking mouse
trap around it should be fine.
As for attackers,  mice sure but not lions, tigers and bears.


 Have fun.



-- 
  T o m    M i t c h e l l
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