We have always specified the importance of saving the SHSH blobs (or ECID SHSH) before jailbreaking your iDevice. Saving SHSH blobs is important if you want to jailbreak (by downgrading) your device again, if Apple patches the exploit used by the new unlock and jailbreak tools. If you are wondering why you need to save the SHSH blobs before jailbreaking/upgrading, it is because you wont be able to save SHSH blobs once Apple has released the new firmware (iOS 4.0.1 / iOS 4.1) since Apple stops signing the iOS 4 firmware once the new one has been released, hence negating you to save your iOS Device SHSH files.
How to Save iOS 4 SHSH Blobs on Windows and Mac?
TinyUmbrella has been updated to support the new iOS 4 on iPhone 3GS and iPod touch 2G/3G. iPhone 3G is not supported because you don’t need to save SHSH blobs for iPhone 3G and even for older iPod touch (non MC model).
Follow this step by step guide to save your SHSH blobs (ECID SHSH) of iPhone 3GS, iPod touch 2G/3G on iOS 4 without having to jailbreak your device.
Step 1: Download the latest beta version of TinyUmbrella for Windows, Mac or Linux.
Step 2: Make sure you are running iTunes 9.0 and higher.
Step 3: Start the program and plug in any one of the supported iDevices (iPhone/iPad/iPod touch).
Step 4: Now click on “Save My SHSH”. TinyUmbrella will grab the signature for you. It will be enabled again once a ticket has been generated to save it to saurik’s server.
Simple! Isn’t it? But make sure you save the signature for your iPhone, iPad and iPod touch on file before Apple releases the next firmware.
[via]Redmondpie