The famous downgrade tool TinyUmbrella was recently updated to a new beta version, despite the fact that downgrading iOS 8.x is not yet possible. Saving firmware SHSH blobs is always a safe bet, as one never knows when they might be needed should a downgrade solution be released.
For the time being, jailbreakers are warned to avoid updating iOS. Moving to iOS 8.2 will result in the loss of any installed jailbreak. While TinyUmbrella developer semaphore sees downgrade possibilities on the horizon, at the present time backing up SHSH blobs locally is just insurance. Until a downgrade is released, here are instructions on how to save iOS SHSH blobs with TinyUmbrella:
1. Make sure the latest Java is installed on your computer. Download from Java.com.
4. Connect your iOS device to the computer.
5. Run TinyUmbrella. The software will automatically detect and save all available SHSH blobs for your device.
Successfully saved SHSH blobs will be listed right in the TinyUmbrella window. Three types are normally listed, including Erase, OTA and Update. Remember, only SHSH blobs for firmware currently signed by Apple can be downloaded at any given time.
Now that your jailbroken iOS 8 device is protected, stay tuned for developments in the jailbreak community. If and when a downgrade solution is made available, saved SHSH blobs will be an integral part of the process.
To fetch SHSH from the device
Owners of A7 and A8 devices can grab SHSH blobs for installed firmware directly from their devices. This means SHSH for an unsigned version of iOS can be saved, such as iOS 8.1.2 if it's currently running.
This function is limited to jailbroken devices in the following list: iPhone 5s, iPad Air, iPad Mini 2 (Retina), iPad Mini 3, iPhone 6, iPhone 6 Plus, iPad Air 2.
1. Disconnect the iOS device from the computer.
2. Install Apple File Conduit 2 from Cydia and respring.
3. Follow the steps above to grab additional SHSH blobs directly from the device.