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Crypt::Rot13 v0.6 - a simple, reversible encryption
use Crypt::Rot13;
my $rot13 = new Crypt::Rot13;
$rot13->charge ("The quick brown fox jumped over the lazy dog.");
print $rot13->rot13 (), "\n";
print $rot13->rot13 (245.333), "\n";
print $rot13->peek (), "\n";
open (F, "/etc/passwd") or die "$!"; $rot13->charge (<F>); close (F) or die "$!"; print $rot13->rot13 (-13);
while (<STDIN>) {
$rot13->charge ($_);
print $rot13->rot13 ();
}
$rot13->charge ('a' .. 'z');
foreach (0 .. 26) {
print $rot13->rot13 ($_), "\n";
}
rot13 is a simple encryption in which ASCII letters are rotated 13 places (see below). This module provides an array object with methods to encrypt its string elements by rotating ASCII letters n places down the alphabet.
Think of it this way: all of the letters of the alphabet are arranged in a circle like the numbers of a clock. Also like a clock, you have a hand pointing at one of the letters: a. Crypt::Rot13 turns the hand clockwise n times through 'b', 'c', 'd', etc, and back again to 'a', 26 turns later.
Crypt::Rot13 turns this hand for every letter of every string it contains a given number of times, the default of which is 13, or exactly half the number of letters in the alphabet.
This creates a Crypt::Rot13 object, which is a blessed array
reference. Any arguments given to new define the array, which is
defaultly empty.
Any arguments given to charge define the array. If no arguments are
passed, the Crypt::Rot13 array will be empty. The arguments can be
non-strings; see the following example.
my $rot13 = Crypt::Rot13->new ({'foo' => 'bar'}, 111);
print $rot13->peek (), "\n", $rot13->rot13 (), "\n";
This dereferences and returns the Crypt::Rot13 object.
(In case you are wondering, the strange method names of peek and
charge are derived from my original conception of Crypt::Rot13 as a
magical device.)
Rotates ASCII alphabetical characters of each element of the array
degree times and returns the changed array without altering the
Crypt::Rot13 object. The degree can be negative and a fractional part
is ignored (to be precise, chr and % ignore it).
Degrees effectively equal to 13 are optimized to a tr///.
Degrees effectively equal to 0 are optimized into a peek.
A degree $d is ``effectively equal'' to 13 if $d % 26 == 13.
Copyright (C) 1999-2000 Julian Fondren
This program 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.
This program 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 this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
The algorithm of rot13 isn't very easy to understand.
Julian Fondren
perl(1) rot13(1)