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        @{$self->{KEY}}[$_] = _rand (2**32) for (0..7);
    }
} 

sub SScrypt {
    my ($self, $data, $decrypt) = @_;
    my ($i, $j, $d1, $d2, $text) = 0;

    croak "Usage: \$gost->SScrypt(\$data)" unless ref $self && defined $data;

    for ($i = 0; $i < length $data; $i += 8) {
        $j = 0;
        $d1 = _longint($data, $i);
        $d2 = _longint($data, $i+4);

        for (1..32) {
            $j = ($_%8) - 1; $j = 7 if $j == -1;
            if ($decrypt) { $j = (32-$_)%8 if $_ >=  9; }
            else          { $j =  32-$_    if $_ >= 25; }

            if ($_%2 == 1) { $d2 ^= $self->_sub($d1 + $self->{KEY}[$j]) }
            else           { $d1 ^= $self->_sub($d2 + $self->{KEY}[$j]) }
        }

        $text .= pack "L2", $d2, $d1;
    }
    return $text;
}

sub SSdecrypt {
    my ($self, $data) = @_;
    croak "Usage: \$gost->SSdecrypt(\$data)" unless ref $self && defined $data;

    $self->SScrypt($data, 1);
}

1;

__END__

=head1 NAME

Crypt::GOST - The GOST Encryption Algorithm

=head1 SYNOPSIS

use Crypt::GOST;

$cipher = Crypt::GOST->new($key);

$ciphertext = $cipher->encrypt($plaintext);

$plaintext  = $cipher->decrypt($ciphertext);

=head1 DESCRIPTION

GOST 28147-89 is a 64-bit symmetric block cipher with a 256-bit key
developed in the former Soviet Union. Some information on it is
available at <URL:http://vipul.net/gost/>.

This module implements GOST encryption. It supports the Crypt::CBC
interface, with the functions described below. It also provides an
interface that is backwards-compatible with Crypt::GOST 0.41, but its
use in new code is discouraged.

=head2 Functions

=over

=item blocksize

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

=item keysize

Returns the size (in bytes) of the key (32, in this case).

=item new($key)

This creates a new Crypt::GOST object with the specified key.

=item encrypt($data)

Encrypts blocksize() bytes of $data and returns the corresponding
ciphertext.

=item decrypt($data)

Decrypts blocksize() bytes of $data and returns the corresponding
plaintext.

=back

=head1 SEE ALSO

Crypt::CBC, Crypt::Twofish, Crypt::TEA

=head1 ACKNOWLEDGEMENTS

=over 4

=item Vipul Ved Prakash

For writing Crypt::GOST 0.41, and reviewing the current version.

=back

=head1 AUTHOR

Abhijit Menon-Sen <ams@wiw.org>

Copyright 2001 Abhijit Menon-Sen. All rights reserved.

This software is distributed under the terms of the Artistic License
<URL:http://ams.wiw.org/code/artistic.txt>.