Code signing your app assures users that it's from a known source and hasn’t been modified since it was last signed. Before your app can integrate app services, be installed on a device, or be submitted to the App Store, it must be signed with a certificate issued by Apple.
To avoid potential issues with common tasks involving code signing, follow these best practices:
Signing and running development builds
Essential guides and documentation
Worldwide Developer Relations Certification Intermediate Certificate update
For details about the intermediate certificate update, visit the Certificate Expiration support page.