NAME

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

ABSTRACT

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

SYNOPSIS

    use Crypt::Skipjack;

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

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.

Functions

blocksize

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

keysize

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

encrypt($data)

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

decrypt($data)

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

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);

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);

MORE EXAMPLES

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

SEE ALSO

Crypt::Khazad, Crypt::Anubis, Crypt::Noekeon and Crypt::Misty1.

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.