Originally Posted by DuckieTigger
The whole idea was: remove Amazon key from the locker, unpack new update file, add in a patch to install the jailbreak again as last step and remove Amazon key again). That modified update file could not be distributed though (copyright and all) - but a patch file for exploded update.bin can be. (or preferably a drop in folder)
PW updates are recovery updates, meaning theirs validity is also checked with key contained in kernel image.
So you can't repack PW updates without either converting them into non-recovery updates (non-trivial task) or replacing currently installed stock kernel with modified, containing non-Amazon key for checking recovery update validity (over-engineered solution, IMHO; it's also a little bit frightening to flash new kernel on PW without easy access to USB downloader mode in case of accidental failure).