A German team of hackers calling themselves doulCi, the latter behind the iCloud bypass activation, has succeeded to generate a downgrade for iPhone 4s running iOS 7.1.1 to iOS 5.1.1 without the need of the digital certificate SHSH blobs. The event has a great importance for the jailbreak community while Apple failed again  to ban "rollback" versions of its  operating system iOS.

SHSH - a digital certificate (or digital signature) is nothing but an obstacle to downgrade firmware.

When you try to restore an iPhone or iPad, iTunes sends the request to Apple server containing information about your device. In response, iTunes sends back the certificate SHSH blobs, which allow the installation of a specific firmware that is current approved by Apple servers. In other words, when you try to install iOS 6.x today, for example, iTunes will give a 3194 error - the device is not eligible for the requested Installation.

The German hackers and even provided video evidence that they could establish iOS 5.1.1 on iPhone 4s without generating a digital certificate SHSH blobs.We can assume that the vulnerability lies in the mechanism of interaction between Apple servers and  devices. doulCi maybe soon present the first public tools for downgrade iOS.

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Mohcine Ariani

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