tpm2_pcrextend - Man Page

Extends a PCR.


tpm2_pcrextend [Options] PCR_DIGEST_SPEC


tpm2_pcrextend(1) - Extends the pcrs with values indicated by PCR_DIGEST_SPEC.

A PCR_DIGEST_SPEC is defined as follows:

The algorithm hash specification is as follows: * The algorithm friendly name or raw numerical. * An equals sign. * The hex hash value.

Example Digest Specification


Note: Multiple specifications of PCR and hash are allowed. Multiple hashes cause the PCR to be extended with both hashes. Multiple same PCR values cause the PCR to be extended multiple times. Extension is done in order from left to right as specified. At most 5 hash extensions per PCR entry are supported. This is to keep the parser simple.


This tool accepts no tool specific options.

Common Options

This collection of options are common to many programs and provide information that many users may expect.

TCTI Configuration

The TCTI or “Transmission Interface” is the communication mechanism with the TPM. TCTIs can be changed for communication with TPMs across different mediums.

To control the TCTI, the tools respect:

  1. The command line option -T or --tcti
  2. The environment variable: TPM2TOOLS_TCTI.

Note: The command line option always overrides the environment variable.

The current known TCTIs are:

The arguments to either the command line option or the environment variable are in the form:


Specifying an empty string for either the <tcti-name> or <tcti-option-config> results in the default being used for that portion respectively.

TCTI Defaults

When a TCTI is not specified, the default TCTI is searched for using dlopen(3) semantics. The tools will search for tabrmd, device and mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query what TCTI will be chosen as the default by using the -v option to print the version information. The “default-tcti” key-value pair will indicate which of the aforementioned TCTIs is the default.

Custom TCTIs

Any TCTI that implements the dynamic TCTI interface can be loaded. The tools internally use dlopen(3), and the raw tcti-name value is used for the lookup. Thus, this could be a path to the shared library, or a library name as understood by dlopen(3) semantics.

Tcti Options

This collection of options are used to configure the various known TCTI modules available:

PCR bank specifiers


Extend PCR 4’s SHA1 bank with a hash

tpm2_pcrextend 4:sha1=f1d2d2f924e986ac86fdf7b36c94bcdf32beec15

Extend PCR 4’s SHA1 and SHA256 banks with hashes

tpm2_pcrextend 4:sha1=f1d2d2f924e986ac86fdf7b36c94bcdf32beec15,sha256=b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c

Extend PCR 4’s SHA1 and PCR 7’s SHA256 bank with hashes

tpm2_pcrextend 4:sha1=f1d2d2f924e986ac86fdf7b36c94bcdf32beec15 7:sha256=b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c


Tools can return any of the following codes:


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tpm2-tools General Commands Manual