Semaphore has released TinyUmbrella v4.21.13 which can now save iOS 4.3 GM (Gold Master) SHSH blobs. The new version of TinyUmbrella automatically uses system proxy settings when launching its loader. Semaphore has also applied few tweaks to streamline the currently saved SHSHs.
To save iOS 4.3 SHSH blobs, just connect your iDevice to your PC or Mac via USB cable and launch TinyUmbrella application. Once your iDevice has been successfully identified by TinyUmbrella, click on your iDevice name from the side-panel and hit the Save SHSH button. Wait while TinyUmbrella saves iOS 4.3 GM SHSH blobs for your iDevice.
Note that in order to save iOS 4.3 GM SHSH blobs, you do not need to have a jailbroken iDevice. No matter what firmware your iDevice is running, TinyUmbrella is well capable of saving iOS 4.3 SHSH blobs in any case. When you hit the Save SHSH button, TinyUmbrella saves iOS 4.3 GM SHSH blobs for your iPhone, iPod Touch or iPad locally and sends a request to Cydia server to have the SHSH files as well. Why you need to save SHSH blobs of iOS 4.2.1 and iOS 4.3 GM? Read here