public function getJwtVerificationKeys()
    {
        $factory = $this->getRequestFactory();
        $request = $factory->getRequestWithOptions('get', 'https://login.windows.net/common/discovery/keys', []);

        $response = $this->getParsedResponse($request);

        $keys = [];
        foreach ($response['keys'] as $i => $keyinfo) {
            if (isset($keyinfo['x5c']) && is_array($keyinfo['x5c'])) {
                foreach ($keyinfo['x5c'] as $encodedkey) {
                    $cert =
                        '-----BEGIN CERTIFICATE-----' . PHP_EOL
                        . chunk_split($encodedkey, 64,  PHP_EOL)
                        . '-----END CERTIFICATE-----' . PHP_EOL;

                    $cert_object = openssl_x509_read($cert);

                    if ($cert_object === false) {
                        throw new \RuntimeException('An attempt to read ' . $encodedkey . ' as a certificate failed.');
                    }

                    $pkey_object = openssl_pkey_get_public($cert_object);

                    if ($pkey_object === false) {
                        throw new \RuntimeException('An attempt to read a public key from a ' . $encodedkey . ' certificate failed.');
                    }

                    $pkey_array = openssl_pkey_get_details($pkey_object);

                    if ($pkey_array === false) {
                        throw new \RuntimeException('An attempt to get a public key as an array from a ' . $encodedkey . ' certificate failed.');
                    }

                    $publicKey = $pkey_array ['key'];

                    $keys[$keyinfo['kid']] = $publicKey;
                }
            }
        }

        return $keys;
    }