Continuing with recent custom, Apple has stopped "code-signing" iOS 8.2 for security reasons. The move, intended to protect users, does make downgrading back to earlier versions impossible, and prevents users with jailbroken devices in iOS 8.2 from updating. The code-signing procedure, which applies to both Apple and iOS or OS X developers, is designed to prevent malicious apps from masquerading as legit ones, or for outside parties to inject code into applications.
