This is where the concept of the "Signing Window" comes in. Apple generally only signs the latest version of iOS. If iOS 17.0 is out, they will stop signing iOS 16.5. Once Apple stops signing a version, they stop generating SHSH blobs for it.
Without the ECID, Apple wouldn't be able to distinguish your iPhone from the millions of others, and security certificates couldn't be unique to your device. shsh host ecid
Apple uses the ECID to sign firmware files specifically for your device. When you click "Update" on your iPhone, your device talks to Apple’s servers (TSS) and says, "Hi, I am device #12345. Please let me install iOS 16.5." Apple checks that number, ensures you are allowed to install that version, and sends back a personalized pass. This is where the concept of the "Signing Window" comes in
Understanding the relationship between , hosting servers , and your device's ECID is fundamental for anyone interested in iOS jailbreaking or downgrading. These components form the backbone of Apple’s security architecture and the tools used to bypass it. What are SHSH Blobs? Once Apple stops signing a version, they stop