07-15-2010, 11:33 PM
john-o,
You are right, this is all can be very confusing.
Apple uses a verification process to determine if a firmware file can be installed on an iPhone. Those verification servers essentially signs the firmware file so that it can be installed. The SHSH files (or blobs as they are often called) contain the needed info specific to one's phone and firmware.
If you wanted to install an older firmware onto your iPhone, (for example, to take advantage of a jailbreak exploit in an older firmware that does not exist in a current firmware) without the SHSH files, Apple would not sign the request and force you to use the current firmware.
Essentially, the SHSH files are a safety net that allows one to roll back to an older firmware, assuming one already as the SHSH files for the older firmware.
You are right, this is all can be very confusing.
Apple uses a verification process to determine if a firmware file can be installed on an iPhone. Those verification servers essentially signs the firmware file so that it can be installed. The SHSH files (or blobs as they are often called) contain the needed info specific to one's phone and firmware.
If you wanted to install an older firmware onto your iPhone, (for example, to take advantage of a jailbreak exploit in an older firmware that does not exist in a current firmware) without the SHSH files, Apple would not sign the request and force you to use the current firmware.
Essentially, the SHSH files are a safety net that allows one to roll back to an older firmware, assuming one already as the SHSH files for the older firmware.