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A comment on TPM on Embedded Systems: Pitfalls and Caveats to Watch Out For. Parent comment

Re:TPM on Embedded Systems: Pitfalls and Caveats to Watch Ou... by amluto on Wednesday January 21, 2026 @02:47PM (#46710601)
That helps with FDE (except to the extent that one might want to connect an encrypted device after boot), but it doesn't help in the slightest with SSH keys. The TPM has nothing remotely resembling per-user PCRs.
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Re:TPM on Embedded Systems: Pitfalls and Caveats to Watch Ou... by Foxboron on Wednesday January 21, 2026 @03:34PM (#46711164)
> The TPM has nothing remotely resembling per-user PCRs.

The system could extend one of the PCRs, or an NVPCR, with some unique user credential locked to the user directory. Then you can't recreate the PCR records in any immediate way.

But you can't just recreate a key under one of the hierarchies anyway. You still need to posses the keyfile.

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Re:TPM on Embedded Systems: Pitfalls and Caveats to Watch Ou... by amluto on Wednesday January 21, 2026 @05:33PM (#46712582)
> The system could extend one of the PCRs, or an NVPCR, with some unique user credential locked to the user directory. Then you can't recreate the PCR records in any immediate way.

Sure, but can the system context-switch that PCR between two different users?

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Re:TPM on Embedded Systems: Pitfalls and Caveats to Watch Ou... by Foxboron on Tuesday January 27, 2026 @05:01PM (#46787601)
> Sure, but can the system context-switch that PCR between two different users?

Right, no it can't.

But this was not really something the TPM was suppose to solve.

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