Re: Is this as insecure as it sounds (was FWD: Complete Fax Privacy Draws C

[Simon Spero <ses@tipper.oit.unc.edu>]

If the plastic sheet is just a fixed mask, then this scheme yields 
instantly to chosen  plain-text (just send an all-black page), really 
quickly to known-plaintext, and pretty quickly to multiple cyphertexts.

There's got to be more to it than that

Simon

(defun modexpt (x y n)  "computes (x^y) mod n"
  (cond ((= y 0) 1) 	((= y 1) (mod x n))
	((evenp y) (mod (expt (modexpt x (/ y 2) n) 2) n))
	(t (mod (* x (modexpt x (1- y) n)) n))))