5 - ROT1: The Root-of-Trust Signed-Image Trailer
This is the only format in the series with a real adversary.
Everything else here is built to survive accidents: a file truncated by a yanked SD card, a corrupt index, a decompression bomb. Those threat models all stop politely short of somebody who actually means it. Firmware signing does not get that luxury, and the post works through what that changes – including why a checksum is not a weaker version of a signature but a different thing entirely, and why the rollback counter has to sit inside the signed material. Every byte in the worked example comes from a throwaway key generated into a temp directory; no real signing key appears anywhere in this post.
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