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You can combine it all in a chip like the Apple T2 and then you would have to somehow probe the silicon, which is of course impossible. (Until you discover that

You can combine it all in a chip like the Apple T2 and then you would have to somehow probe the silicon, which is of course impossible. (Until you discover that the chip has some critical, unfixable software vulnerability like the T2) You can also pair the chip and the CPU at the factory or on initial powerup and have them communicate encrypted from thereon. This is a bit like the iPhone 13 display having some FaceID chip on it where a replacement with a wholly new display will leave FaceID non-functioning.

dev_tty01 5y ago
It is difficult to probe but not at all impossible. However, you can sometimes extract keys by monitoring the chip power supply current over a large number of crypto operations. Much easier than probing the chip internals. https://scholar.google.com/scholar?as_q=%22Differential+Power+Analysis%2C%22&as_occt=title&hl=en&as_sdt=0%2C31 https://scholar.google.com/scholar?as_q=%22Differential+Powe...
XMPPwocky 5y ago
probing silicon is just hard and expensive, not impossible! - though those might be similar enough for most purposes
- R0b0t1 5y ago
  Machines cost tens of millions or more, renting time on them at least hundreds of thousands.
  - Avery3R 5y ago
    I thought FIBs usually cost under $500k?
  - hyperman1 5y ago
    If this is what it takes to hack the TPM, the market for these machines will get bigger. That causes the price to drop. People will find a way. In the end, if a target gets big enough, someone will do it.
my123 5y ago
> You can combine it all in a chip like the Apple T2 and then you would have to somehow probe the silicon For the T2, at least macOS uses a key derived from useryou need both chip control _and_ user password to get in) Windows does not, relying instead on TPM only in a default BitLocker configuration. (with a PIN option via Group Policy, not part of the regular flow) As of why that's bad: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38632 https://msrc.microsoft.com/update-guide/vulnerability/CVE-20...

dev_tty01 5y ago

It is difficult to probe but not at all impossible. However, you can sometimes extract keys by monitoring the chip power supply current over a large number of crypto operations. Much easier than probing the chip internals. https://scholar.google.com/scholar?as_q=%22Differential+Power+Analysis%2C%22&as_occt=title&hl=en&as_sdt=0%2C31 https://scholar.google.com/scholar?as_q=%22Differential+Powe...

XMPPwocky 5y ago

probing silicon is just hard and expensive, not impossible! - though those might be similar enough for most purposes

R0b0t1 5y ago
Machines cost tens of millions or more, renting time on them at least hundreds of thousands.
- Avery3R 5y ago
  I thought FIBs usually cost under $500k?
- hyperman1 5y ago
  If this is what it takes to hack the TPM, the market for these machines will get bigger. That causes the price to drop. People will find a way. In the end, if a target gets big enough, someone will do it.

my123 5y ago

> You can combine it all in a chip like the Apple T2 and then you would have to somehow probe the silicon For the T2, at least macOS uses a key derived from useryou need both chip control _and_ user password to get in) Windows does not, relying instead on TPM only in a default BitLocker configuration. (with a PIN option via Group Policy, not part of the regular flow) As of why that's bad: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38632 https://msrc.microsoft.com/update-guide/vulnerability/CVE-20...