Recently, Saurik, the creator of Cydia, posted a new blog entry explaining the history of Cydia's TSS caching capabilities. As you know, Cydia has been able to automatically save off SHSH blobs for potential downgrade ability with jailbroken devices.
Things have changed rapidly over the years as iOS' security evolved. The earlier versions of iOS included absolutely no downgrade protection. Eventually, with the adaption of TSS, basic verification to make sure that you were installing newer firmware, instead of older firmware arrived. This security was enhanced further with the adoption of a new verification scheme — APTicket — which has proved to be a pain in the rear for would be downgraders. Yes, there have been, and will always be a few exceptions to that rule, but for the most part, Apple has done a good job of cutting off the ability to downgrade firmware.
What does all of this have to do with Cydia's new TSS Center? Well as it turns out, the APTickets saved for iOS 6.0-6.1.2 are all "useless", as they're incomplete tickets unsuitable for booting a device.
In a post on his blog named Where did my iOS 6 TSS data go? Saurik explains in verbose detail the issue at hand...
