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PHP: Methods to encrypt and decrypt with private key (part 1)
Method 2: use arcfour algorithm

function _tutorialspots_2($str, $key)
{
    $s = array();
    for ($i = 0; $i < 256; $i++) {
        $s[$i] = $i;
    }
    $j = 0;
    for ($i = 0; $i < 256; $i++) {
        $j = ($j + $s[$i] + ord($key[$i % strlen($key)])) % 256;
        $x = $s[$i];
        $s[$i] = $s[$j];
        $s[$j] = $x;
    }
    $i = 0;
    $j = 0;
    $res = '';
    for ($y = 0; $y < strlen($str); $y++) {
        $i = ($i + 1) % 256;
        $j = ($j + $s[$i]) % 256;
        $x = $s[$i];
        $s[$i] = $s[$j];
        $s[$j] = $x;
        $res .= $str[$y] ^ chr($s[($s[$i] + $s[$j]) % 256]);
    }
    return $res;
}

Example usage:

echo _tutorialspots_2('your password', 'your private key');

result:

ï·ܹ;vr%¿g

It isn’t a nice result, we need to convert to a nice result:

  • base64_encode
echo base64_encode( _tutorialspots_2('your password', 'your private key') );

Result:

77cOFdy5O3YaciW/Zw==

  • unpack
$unpack = unpack('H*',_tutorialspots_2('your password', 'your private key'));
echo $unpack[1];

Result:

efb70e15dcb93b761a7225bf67

To decrypt, we use this code:

echo _tutorialspots_2('ï·ܹ;vr%¿g','your private key');

We get the result:

your password

If we encrypt the encrypting string with base64_encode function, we use this code:

echo _tutorialspots_2(base64_decode('77cOFdy5O3YaciW/Zw=='),'your private key');

If we encrypt the encrypting string with unpack function, we use this code:

echo _tutorialspots_2(pack('H*','efb70e15dcb93b761a7225bf67'),'your private key');

Next: PHP: Methods to encrypt and decrypt with private key (part 3)

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