If keys are recovered using some form of low level hardware attack, as was almost surely the case here, the attacker can usually recover the unused key sets too.
If the chip manufacturing provisioning supply chain is leaky the new keys will probably be disclosed anyway, and if the key custody chain is broken (ie, keys are shared with OEMs or third parties) they will definitely be disclosed anyway.
Usually this is to allow different departments / divisions / customers (in the case of an OEM model) to all sign code or encrypt binaries, although this is likewise a bit off as each enrolled key increases the amount of material which is available to leak in the leak model. Or to allow model line differentiation with crossover.
HSMs come in all sizes, from a chip in your phone (secure element) or even a dedicated part of a SoC chip, to a big box in a datacenter that can handle tons of requests per second.
The idea is having dedicated hardware to protect the private key material. This hardware can execute signing operations, so it can use the key but it can't share the key material itself. It is usually also physically hardened with techniques to extract said keys, like sidechannel attacks based on power draw, X-ray inspection, decapping etc.
This also sounds very AI-like
I don't really get why anyone would let an AI put random comments on discussions anyway but that's another story.
(I guess)
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.
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://www.chromium.org/developers/design-documents/tpm-usa...
All this is basically a fragile anti-user timebomb that will only generate more avoidable e-waste eventually.
(Although ideally they would itself trap that functionality behind a fuse, so you have to opt-in but can't be opted out.)
Firmware v2 requires a switch with no more than one fuse blown and blows the first fuse.
If you install v2, you can't install v1.
Nintendo can make 22 firmware releases that disallow rollback.
> By default, the boot ROM will only consider bootloader entries with a version field that matches the version field of the first entry, and will stop iterating through the entries is a mismatch is found. The intent is to ensure that if some subset of the bootloader entries are upgraded, and hence the version field of their entries is modified, then the boot ROM will only boot the most recent version of the bootloader. This prevents an accidental rollback to an earlier version of the bootloader in the face of boot memory read errors, corruption, or tampering. Observe that this relies on upgraded bootloader entries being placed contiguously at the start of the array.
[0] https://http.download.nvidia.com/tegra-public-appnotes/tegra...
> According to The Cybersec Guru, this is an unpatchable problem for Sony, because these keys cannot be changed and are burned directly in the APU.
I'm just speculating at this point, but what could prevent Sony from anticipating this exact situation and burning several keys in the APU? I mean, eFuse is not exactly a new technology. That way, once a key is leaked, Sony could push a firmware update switching the APU to a new key which hasn't been leaked yet.