Provided by: tpm2-tools_5.4-1_amd64 bug

NAME

       tpm2_ecdhzgen(1)  -  Recovers  the  shared  secret  value  (Z)  from  a public point and a
       specified private key.

SYNOPSIS

       tpm2_ecdhzgen [OPTIONS]

DESCRIPTION

       tpm2_ecdhzgen(1) - Recovers the shared  secret  value  (Z)  from  a  public  point  and  a
       specified  private  key.   It will perform the multiplication of the provided inPoint (QB)
       with the private key (ds) and return the coordinates of the resultant point (Z = (xZ , yZ)
       ≔ [hds]QB; where h is the cofactor of the curve).

OPTIONS

-c, --key-context=FILE:

         Context  object  pointing  to  ECC  key.  Either a file or a handle number.  See section
         “Context Object Format”.

       • -p, --key-auth=AUTH:

         The authorization value for the ECC key object.

       • -u, --public=FILE:

         Output ECC point Q.

       • -o, --output=FILE

         Specify file path to save the calculated ecdh secret or Z point.

       • --cphash=FILE

         File path to record the hash of the command parameters.   This  is  commonly  termed  as
         cpHash.   NOTE:  When  this  option  is selected, The tool will not actually execute the
         command, it simply returns a cpHash.

   References

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.

   Asymmetric
       • rsa

       • ecc

   Symmetric
       • aes

       • camellia

       • sm4

   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

       • sm2

   Asymmetric Encryption Schemes
       • oaep

       • rsaes

       • ecdh

   Modes
       • ctr

       • ofb

       • cbc

       • cfb

       • ecb

   Misc
       • 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.

       • sm4 - Default SM4: sm4128

       • sm4128 or sm4_128 <mode> - 128 bit SM4 with  optional  mode  (ctr|ofb|cbc|cfb|ecb).   If
         mode is not specified, defaults to null.

       • ecc - Elliptical Curve, defaults to ecc256.

       • ecc192 or ecc_nist_p192 - 192 bit ECC NIST curve

       • ecc224 or ecc_nist_p224 - 224 bit ECC NIST curve

       • ecc256 or ecc_nist_p256 - 256 bit ECC NIST curve

       • ecc384 or ecc_nist_p384 - 384 bit ECC NIST curve

       • ecc521 or ecc_nist_p521 - 521 bit ECC NIST curve

       • ecc_sm2 or ecc_sm2_p256 - 256 bit SM2 curve

       • rsa - Default RSA: rsa2048

       • rsa1024 - RSA with 1024 bit keysize.

       • rsa2048 - RSA with 2048 bit keysize.

       • rsa3072 - RSA with 3072 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

       • sm2

   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.

   Examples
   Create an rsa2048 key with an rsaes asymmetric encryption scheme
       tpm2_create -C parent.ctx -G rsa2048:rsaes -u key.pub -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 key.pub -r key.priv cryptographic
       algorithms ALGORITHM.

COMMON OPTIONS

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

       • -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.  information 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:

       • 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  support  not  using  a  TCTI.   Tools  that do not support it will error when
         attempted to be used without a TCTI 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 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:

       • 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 separated 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.  the various known TCTI modules.

EXAMPLES

              tpm2_createprimary -C o -c prim.ctx -Q

              tpm2_create -C prim.ctx -c key.ctx -u key.pub -r key.priv -G ecc256:ecdh

              tpm2_ecdhkeygen -u ecdh.pub -o ecdh.priv -c key.ctx

              tpm2_ecdhzgen -u ecdh.pub -o ecdh.dat -c key.ctx

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)