cgit.sxemacs.org Git - packages/blob - xemacs-packages/ecrypto/rander.el

   1 ;;;  rander.el -- possibly better random numbers, using rc16 as a RNG
   2
   3 ;; Copyright (C) 1998 Ray Jones
   4
   5 ;; Author: Ray Jones, rjones@pobox.com
   6 ;; Keywords: RNG, rc4, rc16, stream cipher
   7 ;; Created: 1998-04-14
   8
   9 ;; This program is free software; you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation; either version 2, or (at your option)
  12 ;; any later version.
  13 ;;
  14 ;; This program is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18 ;;
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with this program; if not, you can either send email to this
  21 ;; program's maintainer or write to: The Free Software Foundation,
  22 ;; Inc.; 675 Massachusetts Avenue; Cambridge, MA 02139, USA.
  23
  24
  25 (require 'cl)
  26 (require 'rc16)
  27
  28 (defvar *rander-file* (expand-file-name "~/.emacs.rander"))
  29 (defvar *rander-file-length* 512)
  30
  31 ;;; Initialization of the random state
  32
  33 ;; generate a string with random information in it
  34 (defun rander-noise-string ()
  35   (concat
  36    ;; randomness from before
  37    (if (file-readable-p *rander-file*)
  38        (let ((buf nil))
  39          (unwind-protect
  40              (progn
  41                (setq buf (generate-new-buffer "randerdata"))
  42                (save-excursion
  43                  (set-buffer buf)
  44                  (insert-file-contents-literally *rander-file*)
  45                  (buffer-string)))
  46            (if buf
  47                (let ((kill-buffer-hook nil))
  48                  (kill-buffer buf))))))
  49
  50    ;; allocation randomness
  51    (if (boundp 'cons-cells-consed)
  52        (apply 'concat
  53               (mapcar 'int-to-string
  54                       (list cons-cells-consed
  55                             floats-consed
  56                             intervals-consed
  57                             misc-objects-consed
  58                             string-chars-consed
  59                             symbols-consed
  60                             vector-cells-consed)))
  61        "")
  62
  63    ;; time randomness
  64    (apply 'concat (mapcar 'int-to-string (current-time)))
  65
  66    ;; process randomness
  67    (int-to-string (emacs-pid))))
  68
  69
  70 ;;; Mixin keypress randomness, on the fly
  71
  72 ;; don't use this if your (current-time) is not fine grained in the
  73 ;; microseconds.  or if your computer is particularly slow, and the
  74 ;; pre-command-hook stuff slows it down (unlikely).
  75 (defvar *rander-use-keypress* t)
  76 ;; this number shouldn't be too high, as a call to (rander16) will
  77 ;; have to mixin up to this many values before actually returning
  78 (defvar *rander-keypress-count* 128)
  79 (defvar *rander-keypress-timings*
  80   (and *rander-use-keypress*
  81        (make-vector *rander-keypress-count* 0)))
  82 (defvar *rander-keypress-have* 0)
  83
  84 (defun rander-store-key-time ()
  85   "store keypress timings until we have filled the keypress timings buffer"
  86   (when (< *rander-keypress-have* *rander-keypress-count*)
  87     (aset *rander-keypress-timings*
  88           *rander-keypress-have*
  89           (nth 2 (current-time)))
  90     (incf *rander-keypress-have*)))
  91
  92 (if *rander-use-keypress*
  93     (add-hook 'pre-command-hook 'rander-store-key-time))
  94
  95 ;;; main source of randomness, the rc16 generator
  96 (defvar *rander-initialized* nil)
  97 (defvar *rander-rc16-context* nil)
  98
  99 (defun rander-init ()
 100   (setq *rander-rc16-context* (rc16-create-context))
 101   (rc16-set-key *rander-rc16-context* (rander-noise-string))
 102   (add-hook 'kill-emacs-hook 'rander-write-file)
 103   (setq *rander-initialized* t))
 104
 105 (defun rander16 ()
 106   (if (not *rander-initialized*)
 107       (rander-init))
 108   (when (and *rander-use-keypress*
 109              (not (zerop *rander-keypress-have*)))
 110     ;; mixin all the keypresses we have stored to this point
 111     (dotimes (idx *rander-keypress-have*)
 112       (rc16-mixin *rander-rc16-context*
 113                   (aref *rander-keypress-timings* idx)))
 114     ;; reset the buffer
 115     (setq *rander-keypress-have* 0))
 116
 117   ;; return a random value
 118   (rc16-short *rander-rc16-context*))
 119
 120 (defun rander-write-file ()
 121   "write out a seed file for the next time rander is used.  called at
 122 the exit of emacs."
 123   (let ((buf nil))
 124     (unwind-protect
 125         (progn
 126           (setq buf (generate-new-buffer "randerdata"))
 127           (save-excursion
 128             (set-buffer buf)
 129             (dotimes (count *rander-file-length*)
 130               (insert (logand ?\xff (rander16))))
 131             (let ((backup-inhibited t))
 132               (write-file *rander-file*))))
 133       (if buf
 134           (let ((kill-buffer-hook nil))
 135             (kill-buffer buf))))))
 136
 137 (provide 'rander)