Provided by: tpm2-tools_5.6-1build4_amd64 
NAME
tpm2_makecredential(1) - 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 creden‐
tialed-TPM-object(AIK). The privacy is guaranteed due to the fact that only the name of the creden‐
tialed-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) pub‐
lic 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 spe‐
cific 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
• -e, --encryption-key=FILE:
DEPRECATED, use -u or –public instead.
• -u, --public=FILE:
A TPM public key which was used to wrap the seed. NOTE: This option is same as -e and is added to make
it similar with other tools specifying the public key. The old option is retained for backwards com‐
patibility.
• -G, --key-algorithm=ALGORITHM:
The key algorithm associated with TPM public key. Specify either RSA/ ECC. When this option is used,
input public key is expected to be in PEM format and the default TCG EK template is used for the key
properties.
• -s, --secret=FILE or STDIN:
The secret which will be protected by the key derived from the random seed. It can be specified as a
file or passed from stdin.
• -n, --name=FILE:
The name of the key for which certificate is to be created.
• -o, --credential-blob=FILE:
The output file path, recording the encrypted-user-chosen-data and the wrapped secret-data-encryption-
key.
COMMON OPTIONS
This collection of options are common to many programs and provide information that many users may ex‐
pect.
• -h, --help=[man|no-man]: Display the tools manpage. By default, it attempts to invoke the manpager for
the tool, however, on failure will output a short tool summary. This is the same behavior if the “man”
option argument is specified, however if explicit “man” is requested, the tool will provide errors from
man on stderr. If the “no-man” option if specified, or the manpager fails, the short options will be
output to stdout.
To successfully use the manpages feature requires the manpages to be installed or on MANPATH, See
man(1) for more details.
• -v, --version: Display version information for this tool, supported tctis and exit.
• -V, --verbose: Increase the information that the tool prints to the console during its execution. When
using this option the file and line number are printed.
• -Q, --quiet: Silence normal tool output to stdout.
• -Z, --enable-errata: Enable the application of errata fixups. Useful if an errata fixup needs to be
applied to commands sent to the TPM. Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent.
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:
• tabrmd - The resource manager, called tabrmd (https://github.com/tpm2-software/tpm2-abrmd). Note that
tabrmd and abrmd as a tcti name are synonymous.
• mssim - Typically used for communicating to the TPM software simulator.
• device - Used when talking directly to a TPM device file.
• none - Do not initalize a connection with the TPM. Some tools allow for off-tpm options and thus sup‐
port not using a TCTI. Tools that do not support it will error when attempted to be used without a TC‐
TI connection. Does not support ANY options and MUST BE presented as the exact text of “none”.
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 be‐
ing 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 “de‐
fault-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:
• device: For the device TCTI, the TPM character device file for use by the device TCTI can be specified.
The default is /dev/tpm0.
Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“device:/dev/tpm0”
• mssim: For the mssim TCTI, the domain name or IP address and port number used by the simulator can be
specified. The default are 127.0.0.1 and 2321.
Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TCTI=“mssim:host=localhost,port=2321”
• abrmd: For the abrmd TCTI, the configuration string format is a series of simple key value pairs sepa‐
rated by a `,' character. Each key and value string are separated by a `=' character.
• TCTI abrmd supports two keys:
1. `bus_name' : The name of the tabrmd service on the bus (a string).
2. `bus_type' : The type of the dbus instance (a string) limited to `session' and `system'.
Specify the tabrmd tcti name and a config string of bus_name=com.example.FooBar:
\--tcti=tabrmd:bus_name=com.example.FooBar
Specify the default (abrmd) tcti and a config string of bus_type=session:
\--tcti:bus_type=session
NOTE: abrmd and tabrmd are synonymous.
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:
• 0 - Success.
• 1 - General non-specific error.
• 2 - Options handling error.
• 3 - Authentication error.
• 4 - TCTI related error.
• 5 - Non supported scheme. Applicable to tpm2_testparams.
BUGS
Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
HELP
See the Mailing List (https://lists.linuxfoundation.org/mailman/listinfo/tpm2)
tpm2-tools tpm2_makecredential(1)