alt Hacker NewsYes, but console vendors generally prefer not to allow downgrades.
So if v1 is signed by key A, v2 is signed by key B and invalidates key A; a console that installs v2 wouldn't be able to install v1 after, but that's not a problem for Sony.
But, I'm not sure how many companies would be able to manage their keys properly to ensure that someone with access to key A doesn't have access to key B.
If these are asymmetric key pairs and the device side key was extracted from the device... Switching keys wouldn't help, and it's not a huge deal by itself --- having the device side key doesn't allow you to make a firmware image the device would accept.
Fun fact, the Nintendo Switch blows fuses [0] when they do a patch that’s for security/jailbreaking. If I recall there’s something like 12 or 16 fuses they can employ over the life of the product to ensure you can’t rollback updates that prevent piracy. Nvidia builds these fuses into the board.
So if you’ve blown 4 fuses you can’t do a patch that requires only 2 fuses to have blown, it’s a pretty wild solution.
Edit: it’s actually 22 fuses
[0] https://switchbrew.org/wiki/Fuses