tpm2_create - Man Page

Create a child object.


tpm2_create [Options]


tpm2_create(1) - Create a child object. The object can either be a key or a sealing object. A sealing object allows to seal user data to the TPM, with a maximum size of 128 bytes. Additionally it will load the created object if the -c is specified.


These options for creating the TPM entity:

Objects that can move outside of TPM need to be protected (confidentiality and integrity). For instance, transient objects require that TPM protected data (key or seal material) be stored outside of the TPM. This is seen in tools like tpm2_create(1), where the -r option outputs this protected data. This blob contains the sensitive portions of the object. The sensitive portions of the object are protected by the parent object, using the parent’s symmetric encryption details to encrypt the sensitive data and HMAC it.

In-depth details can be found in sections 23 of:

Notably Figure 20, is relevant, even though it’s specifically referring to duplication blobs, the process is identical.

If the output is from tpm2_duplicate(1), the output will be slightly different, as described fully in section 23.


Context Object Format

The type of a context object, whether it is a handle or file name, is determined according to the following logic in-order:

Authorization Formatting

Authorization for use of an object in TPM2.0 can come in 3 different forms: 1. Password 2. HMAC 3. Sessions

NOTE: “Authorizations default to the EMPTY PASSWORD when not specified”.


Passwords are interpreted in the following forms below using prefix identifiers.

Note: By default passwords are assumed to be in the string form when they do not have a prefix.


A string password, specified by prefix “str:” or it’s absence (raw string without prefix) is not interpreted, and is directly used for authorization.




A hex-string password, specified by prefix “hex:” is converted from a hexidecimal form into a byte array form, thus allowing passwords with non-printable and/or terminal un-friendly characters.




A file based password, specified be prefix “file:” should be the path of a file containing the password to be read by the tool or a “-” to use stdin. Storing passwords in files prevents information leakage, passwords passed as options can be read from the process list or common shell history features.


# to use stdin and be prompted

# to use a file from a path

# to echo a password via stdin:
echo foobar | tpm2_tool -p file:-

# to use a bash here-string via stdin:

tpm2_tool -p file:- <<< foobar


When using a policy session to authorize the use of an object, prefix the option argument with the session keyword. Then indicate a path to a session file that was created with tpm2_startauthsession(1). Optionally, if the session requires an auth value to be sent with the session handle (eg policy password), then append a + and a string as described in the Passwords section.


To use a session context file called session.ctx.


To use a session context file called session.ctx AND send the authvalue mypassword.


To use a session context file called session.ctx AND send the HEX authvalue 0x11223344.


PCR Authorizations

You can satisfy a PCR policy using the “pcr:” prefix and the PCR minilanguage. The PCR minilanguage is as follows: <pcr-spec>=<raw-pcr-file>

The PCR spec is documented in in the section “PCR bank specifiers”.

The raw-pcr-file is an optional argument that contains the output of the raw PCR contents as returned by tpm2_pcrread(1).

PCR bank specifiers (


To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifier of:


specifying AUTH.

Algorithm Specifiers

Options that take algorithms support “nice-names”.

There are two major algorithm specification string classes, simple and complex. Only certain algorithms will be accepted by the TPM, based on usage and conditions.

Simple specifiers

These are strings with no additional specification data. When creating objects, non-specified portions of an object are assumed to defaults. You can find the list of known “Simple Specifiers Below”.


  • rsa
  • ecc


  • aes
  • camellia

Hashing Algorithms

  • sha1
  • sha256
  • sha384
  • sha512
  • sm3_256
  • sha3_256
  • sha3_384
  • sha3_512

Keyed Hash

  • hmac
  • xor

Signing Schemes

  • rsassa
  • rsapss
  • ecdsa
  • ecdaa
  • ecschnorr

Asymmetric Encryption Schemes

  • oaep
  • rsaes
  • ecdh


  • ctr
  • ofb
  • cbc
  • cfb
  • ecb


  • null

Complex Specifiers

Objects, when specified for creation by the TPM, have numerous algorithms to populate in the public data. Things like type, scheme and asymmetric details, key size, etc. Below is the general format for specifying this data: <type>:<scheme>:<symmetric-details>

Type Specifiers

This portion of the complex algorithm specifier is required. The remaining scheme and symmetric details will default based on the type specified and the type of the object being created.

  • aes - Default AES: aes128
  • aes128<mode> - 128 bit AES with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null.
  • aes192<mode> - Same as aes128<mode>, except for a 192 bit key size.
  • aes256<mode> - Same as aes128<mode>, except for a 256 bit key size.
  • ecc - Elliptical Curve, defaults to ecc256.
  • ecc192 - 192 bit ECC
  • ecc224 - 224 bit ECC
  • ecc256 - 256 bit ECC
  • ecc384 - 384 bit ECC
  • ecc521 - 521 bit ECC
  • rsa - Default RSA: rsa2048
  • rsa1024 - RSA with 1024 bit keysize.
  • rsa2048 - RSA with 2048 bit keysize.
  • rsa4096 - RSA with 4096 bit keysize.

Scheme Specifiers

Next, is an optional field, it can be skipped.

Schemes are usually Signing Schemes or Asymmetric Encryption Schemes. Most signing schemes take a hash algorithm directly following the signing scheme. If the hash algorithm is missing, it defaults to sha256. Some take no arguments, and some take multiple arguments.

Hash Optional Scheme Specifiers

These scheme specifiers are followed by a dash and a valid hash algorithm, For example: oaep-sha256.

  • oaep
  • ecdh
  • rsassa
  • rsapss
  • ecdsa
  • ecschnorr

Multiple Option Scheme Specifiers

This scheme specifier is followed by a count (max size UINT16) then followed by a dash(-) and a valid hash algorithm. * ecdaa For example, ecdaa4-sha256. If no count is specified, it defaults to 4.

No Option Scheme Specifiers

This scheme specifier takes NO arguments. * rsaes

Symmetric Details Specifiers

This field is optional, and defaults based on the type of object being created and it’s attributes. Generally, any valid Symmetric specifier from the Type Specifiers list should work. If not specified, an asymmetric objects symmetric details defaults to aes128cfb.


Create an rsa2048 key with an rsaes asymmetric encryption scheme

tpm2_create -C parent.ctx -G rsa2048:rsaes -u -r key.priv

Create an ecc256 key with an ecdaa signing scheme with a count of 4 and sha384 hash

/tpm2_create -C parent.ctx -G ecc256:ecdaa4-sha384 -u -r key.priv cryptographic algorithms ALGORITHM.

Object Attributes

Object Attributes are used to control various properties of created objects. When specified as an option, either the raw bitfield mask or “nice-names” may be used. The values can be found in Table 31 Part 2 of the TPM2.0 specification, which can be found here:


Nice names are calculated by taking the name field of table 31 and removing the prefix TPMA_OBJECT_ and lowercasing the result. Thus, TPMA_OBJECT_FIXEDTPM becomes fixedtpm. Nice names can be joined using the bitwise or “|” symbol.

For instance, to set The fields TPMA_OBJECT_FIXEDTPM, TPMA_OBJECT_NODA, and TPMA_OBJECT_SIGN_ENCRYPT, the argument would be:

fixedtpm|noda|sign specifying the object attributes ATTRIBUTES.

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:



In order to create an object, we must first create a primary key as it’s parent.

tpm2_createprimary -c primary.ctx

Create an Object

This will create an object using all the default values and store the TPM sealed private and public portions to the paths specified via -u and -r respectively. The tool defaults to an RSA key.

tpm2_create -C primary.ctx -u -r obj.priv

Seal Data to the TPM

Outside of key objects, the TPM allows for small amounts of user specified data to be sealed to the TPM.

echo "my sealed data" > seal.dat
tpm2_create -C primary.ctx -i seal.dat -u -r obj.priv

Create an EC Key Object and Load it to the TPM

Normally, when creating an object, only the public and private portions of the object are returned and the caller needs to use tpm2_load(1) to load those public and private portions to the TPM before being able to use the object. However, this can be accomplished within this command as well, when supported by the TPM. You can verify your TPM supports this feature by checking that tpm2_getcap(1) commands returns TPM2_CC_CreateLoaded in the command set. If your TPM does not support TPM2_CC_CreateLoaded an unsuported command code error will be returned. If it’s not supported one must use tpm2_load(1). See that manpage for details on its usage.

tpm2_create -C primary.ctx -G ecc -u -r obj.priv -c ecc.ctx

Create an Object and get the public key as a PEM file

This will create an object using all the default values but also output the public key as a PEM file compatible with tools like OpenSSL and whatever supports PEM files.

tpm2_create -C primary.ctx -u -r obj.priv -f pem -o obj.pem


Tools can return any of the following codes:


Github Issues (


See the Mailing List (

Referenced By

tpm2_changeauth(1), tpm2_createak(1), tpm2_duplicate(1), tpm2_import(1), tpm2_loadexternal(1).

tpm2-tools General Commands Manual