tpm2_makecredential - Man Page

Generate the encrypted-user-chosen-data and the wrapped-secret-data-encryption-key for the privacy-sensitive credentialing process of a TPM object.

Synopsis

tpm2_makecredential [Options]

Description

tpm2_makecredential(1) - The TPM supports a privacy preserving protocol for distributing credentials for keys on a TPM. The process guarantees that the credentialed-TPM-object(AIK) is loaded on the same TPM as a well-known public-key-object(EK) without knowledge of the specific public properties of the credentialed-TPM-object(AIK). The privacy is guaranteed due to the fact that only the name of the credentialed-TPM-object(AIK) is shared and not the credentialed-TPM-object's public key itself.

Make-credential is the first step in this process where in after receiving the public-key-object(EK) public key of the TPM and the name of the credentialed-TPM-object(AIK), an encrypted-user-chosen-data is generated and the secret-data-encryption-key is generated and wrapped using cryptographic processes specific to credential activation that guarantees that the credentialed-TPM-object(AIK) is loaded on the TPM with the well-known public-key-object(EK).

tpm2_makecredential can be used to generate the encrypted-user-chosen-data and the wrapped secret-data-encryption-key without a TPM by using the none TCTI option.

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:

<tcti-name>:<tcti-option-config>

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:

Examples

tpm2 createek -Q -c 0x81010009 -G rsa -u ek.pub

tpm2 createak -C 0x81010009 -c ak.ctx -G rsa -g sha256 -s rsassa -u ak.pub \
-n ak.name -p akpass> ak.out

file_size=`ls -l ak.name | awk {'print $5'}`
loaded_key_name=`cat ak.name | xxd -p -c $file_size`

tpm2 readpublic -c 0x81010009 -o ek.pem -f pem -Q

echo "12345678" | tpm2 makecredential -Q -u ek.pem -s - -n $loaded_key_name \
-o mkcred.out -G rsa

Returns

Tools can return any of the following codes:

Bugs

Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)

Help

See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)

Referenced By

tpm2_activatecredential(1).

tpm2-tools General Commands Manual