🚀 go-pugleaf

In article <cW8SR0y00XoCREk38I@andrew.cmu.edu>, jk3k+@andrew.cmu.edu (Joseph G. Keane) writes:
> 
> > How about using the message itself, in some form or another,
> > as the pad.
> > comments?
> 
> Not very secure: all you have to do is guess the first character!  Even if you 
> have a reasonably large key (offset), a known-plaintext attack will get some 
> information, and it propagates forward and backward.
> 
> --Joe

As long as your method of devising a key from the plaintext is arbitrary
(and remains unknown to the cracker) , he will not get his foot in the
door.  What if the n+5th message is the key (again adulterated in some
form) for the nth message?  Any scheme like this will be impregnable
until guessed, and its patterns are certainly unlike those typically
searched for.  The arbitrary system can be changed in encrypted
transmissions (with the acknowledged risk that it will not help IF
the cipher is already compromised).  This denies the "enemy" a large
body of ciphertext to examine for these weak patterns.
  Not by any means the most secure or practical system (more secure than
practical in my mind), but I would put my money on the cleartext
remaining undiscovered for a LONG LONG time.




-- 
amlovell@phoenix.princeton.edu