The Chinese hacker team Pangu released a new jailbreak for devices running on iOS 9.1 a couple days ago. If you own an iPad Pro when it hit the market and have not updated to later versions, you also enjoy the first jailbreak on the 12.9-inch Apple professional tablet.
The reason for launching this jailbreak is none other than closing the exploits used by this group of hackers in later versions of IOS. It is recalled that currently the latest version of iOS available in the market is 9.2.1.
Therefore it is the only version that Apple now allows you to install these on their devices as long as we talk about iPhone 4s or iPad 2 later on. Currently there are several websites like ipsw.me that allow us to download any firmware to install it later in our devices. But if Apple does not sign the installation, the device never activated and never be able to use that version on your iPhone, iPad or iPod Touch.
Since Apple uses this method digitally sign through their firmwares Internet it is impossible to install a higher or lower iOS version that is not being signed at that time. Every time the Cupertino release a new version of iOS, a few days left to sign the previous version quickly.
iPhone Dev team gave an insight on how Apple made it difficult to downgrade to older version of iOS:
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.
This will only affect restores starting at iOS5 and onward, and Apple will be able to flip that switch off and on at will (by opening or closing the APTicket signing window for that firmware, like they do for the BBTicket).
A few years ago it was possible to extract digital signatures to be able to downgrade if necessary, for a while Apple closed that possibility and not any form of power down to an earlier version to the current to jailbreak and take advantage of the launch of this Chinese hacker team.
This jailbreak is still mulling to understand because they have thrown when very few people will have been in that version of IOS which you could not do jailbreak can upgrade to later versions and take advantage of all the news that Apple has been introduced in the different updates.
They claim several non-Chinese hackers, iOS 9.3 beta 6 remains vulnerable to jailbreak. Hopefully when Apple releases the final version, which should not take long, a group of hackers is dedicated to launch officially for those users who enjoy it and have had to update the device to be serviced, as is my case, they can again enjoy the almost endless possibilities for customization that allows us.