Those of you who recently launched Cydia may have received a notice to "See TSS Center (below) to request iOS SHSH", and may be surprised to read the message, "No SHSH seems to be stored for this device".
In a length blog post, Saurik provides some great information about SHSH Blobs, APTickets, and TSS Servers and details what happened. He also notes that iOS 6 APTickets are really only useful for the iPhone 3G[S], iPhone 4, and iPod touch 4G thus far.
At this point, I think I have described everything I need in order to explain the current situation: all of the APTickets Cydia itself requested from Apple for iOS 6 are useless. The word "useless" is important, as it is not accurate to use the word "corrupt": the data that was uploaded was not lost or damaged, and in fact all of the tickets that were stored verified per the algorithm from MuscleNerd.
Instead, the requests being made via Cydia to collect SHSH information for iOS 6 did not result in useful tickets. This is because, in order to better emulate the requests Apple had been making when I first started the service, I filter the manifests I send to Apple to only include information about files that had the partial digests I discussed earlier, as only files that have partial digests are relevant for SHSH.
However, the APTicket signs complete digests, not partial digests, and so even descriptions of files that do not have partial digests need to be sent to TSS to get a complete ticket. What really should therefore be used as a filter is "files with digest information at all", not just those that have partial digests (there is never a partial digest without a full digest), effectively finding all "real" files.
The result is that the APTickets that were downloaded and saved by Cydia itself are not sufficient to boot a device. However, tickets that were downloaded or otherwise obtained by tools such as redsn0w, iFaith, or TinyUmbrella, will work fine. If those tickets are uploaded to Cydia and then downloaded back, they also will continue to work: it is only tickets downloaded by Cydia clients themselves that were affected.
This is a rather unfortunate situation; however, if you followed one of our TinyUmbrella tutorials on saving SHSH Blobs, you should be okay.
At the beginning of his post saurik notes that "I am here to be the bearer of bad news that will likely cause me to get a ton of hatemail". We would strongly urge readers against that; rather, be thankful for everything saurik and other developers have done for the iPhone community.