PHP implements rc4 encryption algorithm_PHP tutorial

php implements the rc4 encryption algorithm. The decryption method of this algorithm is to re-encrypt it once and then it can be restored

Copy to ClipboardQuoted content: [www.bkjia.com] /*
* rc4 encryption algorithm
* $pwd key
* $data data to be encrypted
*/
function rc4 ($pwd, $data)//$pwd key $data needs to be encrypted string
{
$key[] ="";
$box[] ="";

$pwd_length = strlen($pwd);
$data_length = strlen($data);

for ($i = 0; $i < 256; $i++)
{
$key[$i] = ord($pwd[ $i % $pwd_length]);
$box[$i] = $i;
}

for ($j = $i = 0; $i < 256; $i++)
{
$j = ($j + $box[$i] + $key[$i]) % 256;
$tmp = $box[$i];
$box[ $i] = $box[$j];
$box[$j] = $tmp;
}

for ($a = $j = $i = 0; $i < ; $data_length; $i++)
{
$a = ($a + 1) % 256;
$j = ($j + $box[$a]) % 256;

$tmp = $box[$a];
$box[$a] = $box[$j];
$box[$j] = $tmp;

$k = $box[(($box[$a] + $box[$j]) % 256)];
$cipher .= chr(ord($data[$i]) ^ $k);
}

return $cipher;
}

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