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TPM can be asked to perform a “PCR Extend” command, where a particular hash value would be added to the existing hash value in a Platform Configuration Register(PCR), and the resultant hash value can be stored back in the same PCR. i.e.
PCR_Content = PCR_Content || New_Measurement
One can only extend the current value in the PCR with a new hash value, and the existing contents can not be overwritten. This provides us these key capabilities:
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