119 lines
2.7 KiB
Perl
119 lines
2.7 KiB
Perl
# $Id: DES_EDE3.pm,v 1.2 2001/09/15 03:41:09 btrott Exp $
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package Crypt::DES_EDE3;
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use strict;
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use Crypt::DES;
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use vars qw( $VERSION );
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$VERSION = '0.01';
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sub new {
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my $class = shift;
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my $ede3 = bless {}, $class;
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$ede3->init(@_);
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}
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sub keysize { 24 }
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sub blocksize { 8 }
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sub init {
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my $ede3 = shift;
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my($key) = @_;
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for my $i (1..3) {
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$ede3->{"des$i"} = Crypt::DES->new(substr $key, 8*($i-1), 8);
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}
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$ede3;
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}
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sub encrypt {
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my($ede3, $block) = @_;
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$ede3->{des3}->encrypt(
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$ede3->{des2}->decrypt(
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$ede3->{des1}->encrypt($block)
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)
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);
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}
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sub decrypt {
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my($ede3, $block) = @_;
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$ede3->{des1}->decrypt(
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$ede3->{des2}->encrypt(
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$ede3->{des3}->decrypt($block)
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)
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);
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}
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1;
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__END__
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=head1 NAME
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Crypt::DES_EDE3 - Triple-DES EDE encryption/decryption
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=head1 SYNOPSIS
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use Crypt::DES_EDE3;
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my $ede3 = Crypt::DES_EDE3->new($key);
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$ede3->encrypt($block);
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=head1 DESCRIPTION
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I<Crypt::DES_EDE3> implements DES-EDE3 encryption. This is triple-DES
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encryption where an encrypt operation is encrypt-decrypt-encrypt, and
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decrypt is decrypt-encrypt-decrypt. This implementation uses I<Crypt::DES>
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to do its dirty DES work, and simply provides a wrapper around that
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module: setting up the individual DES ciphers, initializing the keys,
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and performing the encryption/decryption steps.
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DES-EDE3 encryption requires a key size of 24 bytes.
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You're probably best off not using this module directly, as the I<encrypt>
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and I<decrypt> methods expect 8-octet blocks. You might want to use the
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module in conjunction with I<Crypt::CBC>, for example. This would be
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DES-EDE3-CBC, or triple-DES in outer CBC mode.
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=head1 USAGE
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=head2 $ede3 = Crypt::DES_EDE3->new($key)
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Creates a new I<Crypt::DES_EDE3> object (really, a collection of three DES
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ciphers), and initializes each cipher with part of I<$key>, which should be
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at least 24 bytes. If it's longer than 24 bytes, the extra bytes will be
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ignored.
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Returns the new object.
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=head2 $ede3->encrypt($block)
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Encrypts an 8-byte block of data I<$block> using the three DES ciphers in
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an encrypt-decrypt-encrypt operation.
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Returns the encrypted block.
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=head2 $ede3->decrypt($block)
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Decrypts an 8-byte block of data I<$block> using the three DES ciphers in
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a decrypt-encrypt-decrypt operation.
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Returns the decrypted block.
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=head2 $ede3->blocksize
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Returns the block size (8).
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=head2 $ede3->keysize
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Returns the key size (24).
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=head1 LICENSE
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Crypt::DES_EDE3 is free software; you may redistribute it and/or modify
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it under the same terms as Perl itself.
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=head1 AUTHOR & COPYRIGHTS
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Crypt::DES_EDE3 is Copyright 2001 Benjamin Trott, ben@rhumba.pair.com. All
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rights reserved.
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=cut
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