3 ms·
that's still less secure, though. without a TPM you have no guarantee of the underlying state of firmware on the device. this enables a persistent backdoor. TP
by logical_person 3y ago
that's still less secure, though. without a TPM you have no guarantee of the underlying state of firmware on the device. this enables a persistent backdoor.
TPM with no PIN is practically bitlocker with no password. A high entropy PIN happens to solve this entire attack.
- ongy 3y agoFor the claim of GGP (stealing out of memory) it's worse, as that's still possible, and there's a bus the key travels over. The PCRs attest system state to the OS, yes. Though the verified boot (PSB/Secure Guard + Secure Boot) chain is supposed to provide the same security there. Provided we assume security features aren't broken by design...
- brohee 3y agoAt least TME-MK and its AMD equivalent are supposed to address in memory key stealing/memory bus snooping (even if it's still unclear to me how the key are generated/stored). There is still decapping and probing the CPU itself but given the size of features is that even remotely doable?
- ongy 3y agoYes and no. Mostly no IMO The memory encryption features are a solution to very specific problems. If the CPU is able to access the memory, then any exploit that gains the execution context of the legitimate user can also access the memory. If it doesn't, the normal memory access control should be enough. I'm iffy on how well they protect against the various side channels. Mostly because I haven't looked far enough into it. IME it protects against cold boot attacks, a theoretic attack of a logic analyzer on the memory bus, and potentially to some degree unbounded reads. But the latter only with very limited gadgets.
- brohee 3y agoYeah I was unclear, it's supposed to address the physical attacks part. If no key leaves the CPU unwrapped, it's down to software exploits and decapping the CPU...
- ongy 3y agoGotcha. Yes There's also this project https://www.cs1.tf.fau.de/research/system-security-group/tresor-trevisor-armored/ https://www.cs1.tf.fau.de/research/system-security-group/tre... which reserves some CPU registers (iirc. A hardware aes accelerator on one core) to prevent key leakage.
- dlgeek 3y agoShould protect against warm boot attacks since the key is supposed to be reset on CPU reboot.