Apple has been moving toward locking down their devices for quite some time, much like iOS 4 became troubling for the iPhone 3GS. According to the Dev Team, iOS 5 betas remove the ability to save SHSH blobs preventing users to downgrade to an older version of iOS through iTunes. The essentially means that you'll be stuck to iOS 4.X to keep your device jailbroken. The next iPhone(s) will come with iOS 5 this fall and will likely be powerless in moving backwards to a previous jailbroken iOS.
APTicket is also changing:
Starting with the iOS5 beta, the role of the “APTicket” is changing — it’s being used much like the “BBTicket” has always been used. The LLB and iBoot stages of the boot sequence are being refined to depend on the authenticity of the APTicket, which is uniquely generated at each and every restore (in other words, it doesn’t depend merely on your ECID and firmware version…it changes every time you restore, based partly on a random number). This APTicket authentication will happen at every boot, not just at restore time. Because only Apple has the crypto keys to properly sign the per-restore APTicket, replayed APTickets are useless.
Jailbreaking through untethered methods will be hindered as iOS 5 updates outside of a restore time, limera1n is the only exception which runs APTicket through the boot sequence. Jailbreaking iOS 5 is going to require a new exploit from the Dev Team for future iDevices jailbreaking and older versions of iTunes.
Versions previous to iOS 5 have been unaffected jailbreaks, hopefully we'll see an iPad 2 Jailbreak before iOS 5 is launched!
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