/**
encrypts / decrypts $text with key ($e, $n)
*/
function encrypt_text($text, $e, $n)
{
$tmp = bi_unserialize($text);
$e = bi_unserialize($e);
$n = bi_unserialize($n);
if (bi_cmp($tmp, $n) >= 0) {
die('$text is too long to encrypt by key with length ' . bi_bit_len($n) . ' bits' . "<br/>\n");
}
return bi_serialize(bi_powmod($tmp, $e, $n));
}
/**
* Returns bit length of number $num
*
* @param big_int resource $num
* @return int
* @access public
*/
function bitLen($num)
{
return bi_bit_len($num);
}
echo '$a andnot $b = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_set_bit($a, 0);
echo 'set_bit($a, 0) = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_clr_bit($a, 0);
echo 'clr_bit($a, 0) = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_inv_bit($a, 0);
echo 'inv_bit($a, 0) = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_subint($a, 10, 20);
echo 'subint($a, 10, 20) = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_rshift($a, 10);
echo '$a >> 10 = [', bi_to_str($c, 2), "]<br/>\n";
$c = bi_lshift($a, 10);
echo '$a << 10 = [', bi_to_str($c, 2), "]<br/>\n";
echo '</div>', "<br/>\n";
echo 'Hamming distance($a, $b) = ', bi_hamming_distance($a, $b), "<br/>\n";
echo 'bit_len($a) = ', bi_bit_len($a), "<br/>\n";
echo 'bit1_cnt($a) = ', bi_bit1_cnt($a), "<br/>\n";
echo 'test_bit($a, 0) = ', bi_test_bit($a, 0), "<br/>\n";
echo 'scan0_bit($a, 0) = ', bi_scan0_bit($a, 0), "<br/>\n";
echo 'scan1_bit($a, 0) = ', bi_scan1_bit($a, 0), "<br/>\n";
echo '<h3>pseudorandom functions</h3>' . "\n";
/*
resource bi_rand(int $bit_len[, string $rand_func_name])
Returns pseudorandom number with $bit_len bit length.
Attention: do not use this function in cryptographic
or security applications! The function can be used only
for educational purposes :)
*/
$c = bi_rand(100);
echo 'rand(100) = ', bi_to_str($c), "<br/>\n";
$c = bi_rand(100, 'mt_rand');