Passing encrypted data by POST in the form in PHP

Question

I am genereting two keys in sha512 and then I put them in separated files. After that I read the public key in the index.php, post the form to the same page and encode the data posted in the input in other form generated only when have the post.

When I try to post the encrypted data to another page, to decryp, nothing happens on the decryp page.

Looks like the encrypted data posted is not valid to the private key.

What I am trying to do is to simulate a comunication between two servers with encrypted data.

Index.php file

    if (isset($_POST['name']) ) {
        $file = fopen('chave_publica.txt', 'r');
        $file2 = fopen('chave_privada.txt', 'r');
        $publicKey =  fread($file,filesize("chave_publica.txt"));
        // $chavePrivada =  fread($file2,filesize("chave_privada.txt"));
        // echo 'Valor digitado: '.$_POST['name'].'<br>';
        // Encrypting
        openssl_public_encrypt($_POST['name'], $criptedData, $publicKey);

        echo $criptedData;
        // decrypting
        // openssl_private_decrypt($criptedData, $decriptado, $chavePrivada);
        // echo '<br>'.'Valor decriptado: '. $decriptado;
    }

<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>

    <!-- <?php echo $criptedData ?> -->
    <?php if (isset($_POST['name']) ) { ?>
        <form method="post" style="margin-top: 20px;" action="decryp.php">
        <textarea name="name"><?php echo $criptedData; ?></textarea>
            <button type="submit">Send</button>
        </form>
    <?php }else{ ?>
        <form method="post" style="margin-top: 20px;" action="index.php" enctype="application/x-www-form-urlencoded">
            <input type="text" name="name" placeholder="Seu nome aqui">
            <button type="submit">Encriptar</button>
        </form>
    <?php } ?>
</body>
</html>

the decryp file

echo $cripted = $_POST['name'];

$file2 = fopen('chave_privada.txt', 'r');
$privateKey =  fread($file2,filesize("chave_privada.txt"));
// $decrypted = 'a';

openssl_private_decrypt($cripted, $decrypted, $privateKey);

echo '<br>'.'Valor decrypted: '. $decrypted;

score 2 · Accepted Answer · answered May 17 '19 at 01:07

For those who are trying to make the post of the encrypted string, will not really work, because when encrypting are generated special characters, these give problem to pass in POST.

The solution I found was to convert the string to hexadecimal and decode it on the other side.

bin2hex("that's all you need");
# 74686174277320616c6c20796f75206e656564

hex2bin('74686174277320616c6c20796f75206e656564');
# that's all you need

PHP convert string to hex and hex to string

from Philippe Gerber

Passing encrypted data by POST in the form in PHP

1 Answers1