TinyUmbrella is a program that allows you to restore an Apple device (iPhone, iPad, iPod Touch, Apple TV) that has been unlocked using the procedure known as Jailbreak, which allows the user to install unofficial applications that are not necessarily in the Store App Store.
There are several reasons why an iPhone user may be interested in restoring the firmware of the device to the previous version, thus undoing the jailbreak that has been applied. These reasons may be some failure in some of the features of the phone, inability to install certain applications, loss of warranty, to test the new iOS that can not yet be done jalibreak and then return to the previous version, for Safety reasons, etc.
Precisely TinyUmbrella is able to take the iPhone to a state before jailbreak, through a downgrade process that performs without leaving traces of the modification of the kernel of the operating system iOS and without iTunes perceives it and therefore denies the operation.
The procedure is to save the SHSH certificates locally on the PC or Mac using the "Save SHSH" option. Then start the TTS server with the option "Start TSS server" (you must close iTunes beforehand and open it after the server starts). You can then select the firmware that you want to install on the iPhone or another Apple device that you want to restore.
This software also serves to exit the recovery mode of iPhone, and to do this you must press the "Exit Recovery" button after selecting the device in the menu to the left of the screen.
Here's a video tutorial on how to save SHSH files.
TinyUmbrella 9.34 is the latest version for Windows (updated in August 2016), which can be downloaded and installed for free, just as for Mac Os X.