🚀 go-pugleaf

In article <C17KGp.3tw@world.std.com>, jcluett@world.std.com (Jim Cluett) writes:
|> Could any of you point me to an encryption program or two,
|> written in BASIC that would be suitable for beginners? Security
|> is not important. Just looking for some introductory material
|> that would be fun and educational for students. Thanks. e-mail to
|> jcluett@world.std.com.
|>  
|>

If someone sends them to you, well and good.  But, this stuff is entirely
suitable for even beginner students to write from scratch if the system
is simple enough.

If no one sends you code, I suggest getting a copy of H F Gaines'
"Cryptography" and looking at any of the following:

  Vigenere (and its variants, possibly excepting Porta)

  Simple Substitution

  Quagmire

  Complete Columnar Transposition

and code them up yourself.

All of these are somewhere between 20 and 50 lines of code in BASIC,
especially if one uses READ/DATA instead of file I/O to provide the input.
Porta is not all that much harder than the rest, but it might be left out
of a beginner's course simply because it has the same security as the others
and is a bit nasty to program.

Also, with a little discipline, one can often use fragments of one program
to do the next one.   Be sure to teach about MID$(a$,i,1) kind of stuff (or
whatever your BASIC has for string manipulation).  If there is a LSET A$=
type command available, it can also be very handy along with MID$(A$,I,1)= exp
kind of stuff.  

You can get by without the fancy string stuff, too, but it is handy sometimes.
(Teaching strategy question:  Do you teach string manipulation, or do you
teach them to extract characters, translated to integers, and manipulate
ordinary integer arrays and then translate back to a string?  Or, let the 
students choose?  For some of these "historical" ciphers, translating the input
to the number string A=0, B=1, ...Z=25 is often the key insight.  In other
systems, one can settle for shuffling the strings).

The other systems in the book can also be done and very few of them would
take over 100 lines of BASIC code to do.


-- 
   Larry W. Loen        |  My Opinions are decidedly my own, so please
                        |  do not attribute them to my employer