是不是所有 iPhone / iPad ，都可以在有 SHSH 的情况下降级到低版本的 iOS？

[ilili]

[Totoria]

不是，A4以上设备全部不可以！

[woorm]

@Totoria touch4 没有 5.1.1的SHSH 是不是没法降级?

[pH]

要真这样，开发者都哭了

[m2q1n9]

iOS5后SHSH就没用了，转用APTicket了
具体可看 http://blog.iphone-dev.org/post/6952986620/blob-monster

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.

[Starduster]

正好相反……是所有在售的iOS设备全部都不能降级，即使你有SHSH……