Updated Certificate for Game Center Authentication
October 31, 2018
On November 12, 2018, a new certificate for server-based Game Center Player ID verification will be available via the publicKeyUrl property of generateIdentityVerificationSignature, and the previous certificate will expire.
Make sure your app always retrieves and uses the current publicKeyUrl value so it automatically uses the new certificate. If your app caches the certificate or hardcodes the certificate URL, it will require an update.