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+;;;; GNU Anubis -- an outgoing mail processor and the SMTP tunnel.
+;;;; Copyright (C) 2003 The Anubis Team.
+;;;;
+;;;; GNU Anubis is free software; you can redistribute it and/or modify
+;;;; it under the terms of the GNU General Public License as published by
+;;;; the Free Software Foundation; either version 2 of the License, or
+;;;; (at your option) any later version.
+;;;;
+;;;; GNU Anubis is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;;; GNU General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU General Public License
+;;;; along with GNU Anubis; if not, write to the Free Software
+;;;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+;;;;
+;;;; GNU Anubis is released under the GPL with the additional exemption that
+;;;; compiling, linking, and/or using OpenSSL is allowed.
+
+(define (rot-13 text)
+ "Encode the text using ROT-13 method"
+ (let ((length (string-length text)))
+ (do ((i 0 (1+ i)))
+ ((>= i length) text)
+ (let ((c (string-ref text i)))
+ (cond
+ ((char-lower-case? c)
+ (string-set! text i
+ (integer->char
+ (+ 97 (modulo (+ (- (char->integer c) 97) 13) 26)))))
+ ((char-upper-case? c)
+ (string-set! text i
+ (integer->char
+ (+ 65 (modulo (+ (- (char->integer c) 65) 13) 26))))))))))
+

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