How to decode aes128gcm?

Question

PHP

Hello!
How can I decode a request from a web push notification if authToken and publicKey are known.

$ciphertext = .....; // тело запроса
$publicKey = 'BCR.....'; // он же p256dh Key
$authToken ='J4E5H.......';
echo openssl_decrypt($ciphertext, "aes-128-gcm",$publicKey, 0, $authToken);

https://jrconlin.github.io/WebPushDataTestPage/
Here the encoding process is described in more detail, but unfortunately nothing works)
This code unfortunately does not produce anything .... maybe someone came across?

Answer 1

The first question is why did you decide that you need a public key if this is asymmetric encryption

Answer 2

No way.
Knowing the public key will not help you - it is public because it is distributed to everyone and without restrictions. You either need a private key, or a brute, or be a math genius...
And first, read about asymmetric encryption...