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package Crypt::Skipjack;

use strict;
use warnings;
require Exporter;

our @EXPORT_OK = qw(keysize blocksize new encrypt decrypt);
our $VERSION = '1.0.2';
our @ISA = qw(Exporter);

require XSLoader;
XSLoader::load('Crypt::Skipjack', $VERSION);

# Preloaded methods go here.

1;

__END__

=head1 NAME

Crypt::Skipjack - Crypt::CBC-compliant block cipher

=head1 ABSTRACT

Skipjack is an 80-bit key, 64-bit block cipher designed by the NSA.

=head1 SYNOPSIS

    use Crypt::Skipjack;

    $cipher = new Crypt::Skipjack $key;
    $ciphertext = $cipher->encrypt($plaintext);
    $plaintext  = $cipher->decrypt($ciphertext);

=head1 DESCRIPTION

Skipjack is the secret key encryption algorithm designed by the
National Security Agency, and is used in the Clipper chip and Fortezza
PC card. It was implemented in tamper-resistant hardware and its
structure had been classified since its introduction in 1993. Skipjack
was unclassified on June 24, 1998.

Skipjack is an 80-bit key, 64-bit block cipher.

This module supports the Crypt::CBC interface, with the following
functions.

=head2 Functions

=over

=item B<blocksize>

Returns the size (in bytes) of the block (8, in this case).

=item B<keysize>

Returns the size (in bytes) of the key (10, in this case).

=item B<encrypt($data)>

Encrypts 8 bytes of $data and returns the corresponding ciphertext.

=item B<decrypt($data)>

Decrypts 8 bytes of $data and returns the corresponding plaintext.

=back

=head1 EXAMPLE 1

    #!/usr/local/bin/perl

    use diagnostics;
    use strict;
    use warnings;
    use Crypt::Skipjack;

    # key must be 10 bytes long
    my $key = "0123456789";

    my $cipher = new Crypt::Skipjack $key;

    print "blocksize = ", $cipher->blocksize, " bytes \n";
    print "keysize = ", $cipher->keysize, " bytes \n";

    # block must be 8 bytes long
    my $plaintext1 = "abcdef01";

    my $ciphertext = $cipher->encrypt($plaintext1);
    my $plaintext2 = $cipher->decrypt($ciphertext);

    print "Decryption OK\n" if ($plaintext1 eq $plaintext2);

=head1 EXAMPLE 2

    #!/usr/local/bin/perl

    use diagnostics;
    use strict;
    use warnings;
    use Crypt::CBC;  # CBC automatically loads Skipjack for us

    # when using Crypt::CBC, key may be of ANY length
    my $key = "0123456789abcdef";

    # IV must be exactly 8 bytes long
    my $IV = pack "H16", 0;

    my $cipher = Crypt::CBC->new({'key' => $key,
                                  'cipher' => 'Skipjack',
                                  'iv' => $IV,
                                  'regenerate_key' => 1,
                                  'padding' => 'standard',
                                  'prepend_iv' => 0
                                });

    # when using Crypt::CBC, plaintext may be of ANY length
    my $plaintext1 = "This is a test";

    my $ciphertext = $cipher->encrypt($plaintext1);
    my $plaintext2 = $cipher->decrypt($ciphertext);

    print "Decryption OK\n" if ($plaintext1 eq $plaintext2);

=head1 MORE EXAMPLES

See B<Crypt::CBC> for more examples using CBC mode. See also the
"examples" and "t" directories for some more examples.

=head1 SEE ALSO

B<Crypt::Khazad>, B<Crypt::Anubis>, B<Crypt::Noekeon> and
B<Crypt::Misty1>.

=head1 COPYRIGHT AND LICENSE

Copyright 2003 by Julius C. Duque <jcduque (AT) lycos (DOT) com>

This library is free software; you can redistribute it and/or modify
it under the same terms as the GNU General Public License.

=cut