The specific iterations of Apple’s mobile operating system that the company officially validates for installation and use are digitally authenticated by Apple. This authentication process confirms that the software originates from Apple and has not been tampered with. For example, if Apple signs iOS 16.6.1, users can generally install or downgrade to that particular version without encountering errors related to authenticity.
Maintaining versions in a signed state is critical for Apple’s security model. It allows the company to control the operating system landscape on its devices, preventing users from installing potentially vulnerable or malicious software. Historically, unsigned versions have been targeted by jailbreakers and those seeking to bypass security restrictions, leading to potential security risks and instability for the operating system. By controlling signing, Apple can safeguard its users and the integrity of its platform.