Golden Ratio Challenge

canine.lisp

;;; http://1.61803398874.com/canine
;;; Copyright Chris Howey
;;; Released under the ISC License
;;;
;;; To build, use buildapp (http://www.xach.com/lisp/buildapp/):
;;; buildapp --output dog --load canine.lisp --entry main
;;;
(defun list-of-output-streams (list-of-files)
  (let ((output-streams nil))
    (dolist (out-file list-of-files output-streams)
      (push (open (parse-namestring out-file) :direction :output :element-type '(unsigned-byte 1) :if-exists :supersede) output-streams))))
(defun usage (command)
  (format *error-output* "Usage: ~%~A FILE... ~%" command))
(defun main (argv)
  (if (= (length argv) 1)
    (usage (first argv))
    (with-open-stream (out-stream (apply #'make-broadcast-stream (list-of-output-streams (rest argv))))
      (loop for val = (read-byte *standard-input* nil)
            while val
            do (write-byte val out-stream))
      (finish-output out-stream))))

Vigenere.lisp

;;; Golden Ratio Challenge: http://1.61803398874.com/
;;; https://en.wikipedia.org/wiki/Vigenère_cipher
;;;
;;; This implements the Vigenere cipher to solve the problem with one addition:
;;; Numbers are translated to letters. By glancing over the wikipedia page
;;; it seems as though the encryption algorithm is meant only for letters.
;;;
;;; Copyright Chris Howey
;;; Released under the ISC License
;;;
;;; EXAMPLES:
;;; (encrypt-message "attackatdawn" "lemonlemonle")
;;; (decrypt-message "xfbhlqtlj" "61803398874")
;;;
(defun normalized-char-code (letter)
  (let ((upletter (char-upcase letter)))
    (if (<= (- (char-code upletter) (char-code #\0)) 9)
      (- (char-code upletter) (char-code #\0))  
      (- (char-int upletter) (char-code #\A)))))
(defun normalized-code-to-char (code)
  (code-char (+ (char-code #\A) code)))
(defun encrypt-char-to-code (message key)
  (mod (+ (normalized-char-code message) (normalized-char-code key)) 26))
(defun encrypt-char (message key)
  (normalized-code-to-char (encrypt-char-to-code message key))  )
(defun encrypt-message (message key)
  (with-output-to-string (s)
    (loop for i from 0 to (- (length message) 1) do 
          (princ (encrypt-char (elt message i) (elt key i)) s))))
(defun decrypt-char-to-code (message key)
  (mod (- (normalized-char-code message) (normalized-char-code key) -26) 26))
(defun decrypt-char (message key)
  (normalized-code-to-char (decrypt-char-to-code message key))  )
(defun decrypt-message (message key)
  (with-output-to-string (s)
    (loop for i from 0 to (- (length message) 1) do 
          (princ (decrypt-char (elt message i) (elt key i)) s))))