Cbenson's data encryption technique (plea for help)

[Jason E. Elliott]

     I don't know whether those that replied to  my  request
for  a  critique  on  my idea behind it.   (I won't post the
program again unless asked to.)

     Being a mere high school student, and not versed passed
pre-calculus,  I wrote my program using ideas suggested by a
book titled  "Cryptanlisis,  A  Mathematical  Approach".   I
looked  at the Vigenere method primarily because it was sim-
ple to implement, but could be made  complicated  enough  to
deter the pirating of my source by other students.  However,
as you all know, the Vigenere method by itself,  is  not  at
all  hard  to  solve.  However, with the twist that makes my
program a little more complicated, the  key  that  the  user
provides  actually is permuted once for each time that it is
used.

     When the key has been used once,  the  key  is  rotated
left  one letter and used again.  Therefore, there is a one-
to-one correspondance between the number of letters  in  the
key, and the number of keys used.

     A dissemination interval equal to the length of the key
is used to make things even more messy.

     In any case, although  this  program  is  primitive  by
today's  standards,  it  does protect my work from my class-
mates.  (As well as impressing the computer teachers.)

     I hope this makes things a little clearer (if there was
any question as to the program's operation).  I would appre-
ciate any advice or constructive criticism that you in  net-
land  might have.  Also, my request still stands with regard
to my desire to get some kind of estimate as to the relative
difficulty  of  deciphering a message coded with my program.
I would also like some help with finding  the  optimum  key-
to-file-length ratio (that is, the best length of key to use
for a given file).



               As they say:  Thanks in advance
               Jason E. Elliott















                        May 14, 1984