I'm trying to [Verifying that requests originate from Office for the web by using proof keys](https://wopi.readthedocs.io/en/latest/scenarios/proofkeys.html)

I have read this resource many times but still do not know how to implement it in PHP.

I tried the code below it didn't seem to solve the problem, I do not know what to do next.

Can someone give me a suggestion?

```
$rsa = new Crypt_RSA();
$modulus = new Math_BigInteger(base64_decode($modulus), 256);
$exponent = new Math_BigInteger(base64_decode($exponent), 256);

$rsa->loadKey(array('n' => $modulus, 'e' => $exponent));
$rsa->setPublicKey();
$publicKey = $rsa->getPublicKey();

```