Yes, and no. If you lose the firmware entirely you would indeed lose the derived decryption keys. But if you keep the firmware somewhere safe (or even fetch i

Yes, and no. If you lose the firmware entirely you would indeed lose the derived decryption keys. But if you keep the firmware somewhere safe (or even fetch it again from wherever you got it first), then loading it again would derive the same keys, and you can decrypt your stuff again. This makes reproducible builds very important by the way: if you rely on a source control system to hold on to old versions of the firmware (just in case someone needs it to decrypt old files), you really really want a way to re-generate the same binary blob from the same source code.