File Coverage

blib/lib/Crypt/Ctr.pm

Criterion	Covered	Total	%
statement	16	16	100.0
branch			n/a
condition	1	3	33.3
subroutine	4	4	100.0
pod	1	1	100.0
total	22	24	91.6

package Crypt::Ctr;
use Crypt::CFB;
use vars qw($VERSION);
@ISA = (Crypt::CFB);

$VERSION = 0.01;

sub _statef;

#
# Crypt::Ctr implements the Counter Mode for block ciphers.
# almost everything is inherited from Crypt::CFB, just the
# _statef method is overloaded.
#
# XXX  the counter is just a perl int. So after roughly two Gigabytes
# of cleartext, the keystream will repeat itself.
#

sub new {
	my ($proto, $key, $algo) = @_;
	my $class = ref($proto) || $proto;
	my $self = new Crypt::CFB ($key, $algo);
	$self->{statef} = \&_statef;
	$self->{fill} = "\x0" x ($self->{registerlength} - 4);
	bless ($self, $class);
}


sub _statef {
	my $self = shift;
	my ($c, undef) = unpack "La*", $self->{register};
	$c++;
	$self->{register} = unpack "a*" , (pack "La*", ($c, $self->{fill}));
}

1;
__END__