sub yubikey_hex2bin
{
        my $in = $_[0];
        my $out = "";
        for(my $k=0;$k<length($in);$k+=2)
        {
                $out .= chr(hex(substr($in,$k,2)));
        }
        return $out;
}

sub yubikey_bin2hex
{
        my $in = $_[0];
        my $out = "";
        for(my $k=0;$k<length($in);$k++)
        {
                $out .= sprintf("%2x",ord(substr($in,$k,1)));
        }
        $out =~ s/ /0/g;        # this is a hack.. not sure why it has to be like this...
        return $out;
}