When booting into recovery mode and installing a ROM zip from my SDcard, it first says I need to mount my /sdcard (when it is mounted), and then it says "signature verification failed", despite my using a stock ROM zip.
Perhaps this has something to do with my obtaining the stock(?) ROM from a possibly untrustworthy third-party site? What is the official download site for Samsung Galaxy S4 (SGH-M919) phones?
thanks in advance for the help
(cf. my other question for more background information)