Understanding NvPCRs in systemd v262
Systemd has introduced NvPCRs, or NvPCR-like registers, in systemd v262 as a solution to the scarcity of TPM PCRs. These NvPCRs are additional registers allocated in the TPM's NV memory and serve as PCR-like registers for event types that are not suitable for real PCRs. This is because some measurements are inherently unpredictable, such as those depending on closed-source vendor firmware or user behavior.
By using NvPCRs, systemd can provide predictable values for local secrets that need to be locked against, without relying on the scarce and insecure real PCRs.
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