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plugins/Tk-Logon/Crypt/Solitaire.pm

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+#------------------------------------------------------------------------------#
+# Crypt::Solitaire
+#
+# Solitaire cryptosystem, as used in Neal Stephenson's novel _Cryptonomicon_
+# Designed by Bruce Schneier (President, Counterpane Systems)
+# Original Perl Code by Ian Goldberg <ian@cypherpunks.ca>, 19980817
+# Minor changes and module-ification by Kurt Kincaid <sifukurt@yahoo.com>
+#
+#       Last Modified:  28-Nov-2001 04:20:10 PM
+#       Copyright(c) 2001, Kurt Kincaid. All Rights Reserved.
+#
+# This is free software and may be modified and/or redistributed under the
+# same terms as perl itself.
+#------------------------------------------------------------------------------#
+
+package Crypt::Solitaire;
+use strict;
+use vars qw($VERSION @ISA @EXPORT @EXPORT_OK $multFactor $k $D $c $v $Deck $text $passphrase $mode $class );
+
+require Exporter;
+
+@ISA       = qw(Exporter AutoLoader);
+@EXPORT_OK = qw(Pontifex);
+
+$VERSION = "2.0";
+
+sub new {
+    ( $class, $passphrase ) = @_;
+    $passphrase =~ y/a-z/A-Z/;
+    $passphrase =~ s/[A-Z]/$k=ord($&)-64,&e/eg;
+    my $self = bless {}, $class;
+    return $self;
+}
+
+sub encrypt {
+    my $self = shift;
+    ( $text, $passphrase ) = @_;
+    return Pontifex( $text, $passphrase, "e" );
+}
+
+sub decrypt {
+    my $self = shift;
+    ( $text, $passphrase ) = @_;
+    return Pontifex( $text, $passphrase, "d" );
+}
+
+sub Pontifex {
+    if ( ref $_[ 0 ] ) {
+        my $self = shift;
+    }
+    ( $text, $passphrase, $mode ) = @_;
+    if ( $mode =~ /^e/i ) {
+        $multFactor = 1;
+    } elsif ( $mode =~ /^d/i ) {
+        $multFactor = -1;
+    } else {
+        return undef;
+    }
+
+    $Deck = pack( 'C*', 33 .. 86 );
+
+    $k = 0;
+
+    $text =~ y/a-z/A-Z/;
+    $text =~ y/A-Z//dc;
+    if ( $multFactor == 1 ) {
+        $text .= "X" while length( $text ) % 5;
+    }
+    $text =~ s/./chr((ord($&)-13+$multFactor*&e)%26+65)/eg;
+
+    if ( $multFactor == -1 ) {
+        $text =~ s/X*$//;
+    }
+    $text =~ s/.{5}/$& /g;
+    return $text;
+}
+
+sub v {
+    $v = ord( substr( $D, $_[ 0 ] ) ) - 32;
+    $v > 53 ? 53 : $v;
+}
+
+sub e {
+    $D =~ s/(.*)U$/U$1/;
+    $D =~ s/U(.)/$1U/;
+
+    $D =~ s/(.*)V$/V$1/;
+    $D =~ s/V(.)/$1V/;
+    $D =~ s/(.*)V$/V$1/;
+    $D =~ s/V(.)/$1V/;
+
+    $D =~ s/(.*)([UV].*[UV])(.*)/$3$2$1/;
+
+    $c = &v( 53 );
+    $D =~ s/(.{$c})(.*)(.)/$2$1$3/;
+
+    if ( $k ) {
+        $D =~ s/(.{$k})(.*)(.)/$2$1$3/;
+        return;
+    }
+
+    $c = &v( &v( 0 ) );
+
+    $c > 52 ? &e : $c;
+}
+
+1;
+__END__
+
+
+=head1 NAME
+
+Crypt::Solitaire - Solitaire encryption
+
+=head1 SYNOPSIS
+
+# OO Interface
+  use Crypt::Solitaire;
+  $ref = Crypt::Solitaire->new( $passphrase );
+  $encrypted = $ref->encrypt( $text );
+  
+  $ref2 = Crypt::Solitaire->new( $passphrase );
+  $decrypted = $ref2->decrypt( $encrypted );
+  
+# Functional Interface
+
+  use Crypt::Solitaire;
+  my $encrypted = Pontifex( $plaintext, $passphrase, $mode );
+
+=head1 DESCRIPTION
+
+Solitaire is a top-notch pencil-and-paper encryption system developed by Bruce Schneier.
+Here is the description in Schneier's own words:
+
+"In Neal Stephenson's novel Cryptonomicon, the character Enoch Root describes a
+cryptosystem code-named "Pontifex" to another character named Randy Waterhouse, and later
+reveals that the steps of the algorithm are intended to be carried out using a deck of
+playing cards. These two characters go on to exchange several encrypted messages using
+this system. The system is called "Solitaire" (in the novel, "Pontifex" is a code name
+intended to temporarily conceal the fact that it employs a deck of cards) and I designed
+it to allow field agents to communicate securely without having to rely on electronics or
+having to carry incriminating tools. An agent might be in a situation where he just does
+not have access to a computer, or may be prosecuted if he has tools for secret
+communication. But a deck of cards...what harm is that? 
+
+"Solitaire gets its security from the inherent randomness in a shuffled deck of cards. By
+manipulating this deck, a communicant can create a string of "random" letters that he
+then combines with his message. Of course Solitaire can be simulated on a computer, but
+it is designed to be implemented by hand. 
+
+"Solitaire may be low-tech, but its security is intended to be high-tech. I designed
+Solitaire to be secure even against the most well-funded military adversaries with the
+biggest computers and the smartest cryptanalysts. Of course, there is no guarantee that
+someone won't find a clever attack against Solitaire, but the algorithm is certainly
+better than any other pencil-and-paper cipher I've ever seen."
+
+Simple system, easy to use, and relatively fast.
+
+=head1 LIMITATIONS
+
+Restricted only to letters A..Z. Lower case letters are converted to upper
+case, and due to the fact that Solitaire applies its own formatting to the text, the
+output can be a little tricky at first glance.
+
+It also should be noted that there is a verified bias in the algorithm. Fore more
+information on this, go here: http://www.ciphergoth.org/crypto/solitaire/
+
+=head1 METHODS
+
+=over 4
+
+=item B<Pontifex> $text, $passphrase, $mode
+
+$text is encrypted using $passphrase.  Encrypts or decrypts, based on $mode.  Mode must
+be set to "e" or "d," for encrypting and decrypting, respectively.
+
+=back
+
+=head1 AUTHOR
+
+Designed by Bruce Schneier (President, Counterpane Systems)
+
+Original Perl Code by Ian Goldberg <ian@cypherpunks.ca>, 19980817
+
+Minor changes and module-ification by Kurt Kincaid <sifukurt@yahoo.com>
+
+=head1 SEE ALSO
+
+perl(1), Counterpane System (http://www.counterpane.com).
+
+=cut
+