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By default, they start out at the highest level of security, assuming an always-on network connection. It can be adjusted downward, which those of us reading HN

By default, they start out at the highest level of security, assuming an always-on network connection. It can be adjusted downward, which those of us reading HN are likely to prefer. Signature verification alone may confirm that a release is from Apple, but it doesn't confirm that the release hasn't been superseded due to security issues. (Or marketing, if you're conspiracy-minded.) The "Medium" setting allows older versions of MacOS, so although the article doesn't say, I suspect that is doing signature-verification alone, and does not require a network connection.

lumisota 9y ago
More about Secure Boot: https://support.apple.com/en-gb/HT208330 https://support.apple.com/en-gb/HT208330
monocasa 9y ago
> Signature verification alone may confirm that a release is from Apple, but it doesn't confirm that the release hasn't been superseded due to security issues. (Or marketing, if you're conspiracy-minded.) But fuse sets will. Thus is how downgrade attacks are generally protected against in high integrity consumer electronics. That way your device continues to work when you reboot and Comcast is down again.
- eridius 9y ago
  I'm sure the T2 doesn't verify the OS against the network at boot time, but rather when you're installing the OS update. Once it's been installed, it's trusted. The trivial proof here is if it did anything else, ignoring an OS update would brick your device, which is obviously not desired behavior.
  - willstrafach 9y ago
    > I'm sure the T2 doesn't verify the OS against the network at boot time, but rather when you're installing the OS update. Once it's been installed, it's trusted. This is correct. Network is only needed for re-install on the high security setting. When already installed, the only verification is to ensure signatures are valid, similar to how iOS devices function (You cannot re-flash/downgrade to an older OS, but if you have an older OS installed, the device will not prevent you from booting).
derefr 9y ago
To be more explicit, this is exactly the same thing browsers (should) do: when verifying a (code-signing or server) certificate, is is proper to also retrieve an up-to-date Certificate Revocation List from the CA.

lumisota 9y ago

More about Secure Boot: https://support.apple.com/en-gb/HT208330 https://support.apple.com/en-gb/HT208330

monocasa 9y ago

> Signature verification alone may confirm that a release is from Apple, but it doesn't confirm that the release hasn't been superseded due to security issues. (Or marketing, if you're conspiracy-minded.) But fuse sets will. Thus is how downgrade attacks are generally protected against in high integrity consumer electronics. That way your device continues to work when you reboot and Comcast is down again.

eridius 9y ago
I'm sure the T2 doesn't verify the OS against the network at boot time, but rather when you're installing the OS update. Once it's been installed, it's trusted. The trivial proof here is if it did anything else, ignoring an OS update would brick your device, which is obviously not desired behavior.
- willstrafach 9y ago
  > I'm sure the T2 doesn't verify the OS against the network at boot time, but rather when you're installing the OS update. Once it's been installed, it's trusted. This is correct. Network is only needed for re-install on the high security setting. When already installed, the only verification is to ensure signatures are valid, similar to how iOS devices function (You cannot re-flash/downgrade to an older OS, but if you have an older OS installed, the device will not prevent you from booting).

derefr 9y ago

To be more explicit, this is exactly the same thing browsers (should) do: when verifying a (code-signing or server) certificate, is is proper to also retrieve an up-to-date Certificate Revocation List from the CA.