wolfTPM

wolfTPM (TPM 2.0)

Portable TPM 2.0 project designed for embedded use.

Project Features

• This implementation provides all TPM 2.0 API's in compliance with the specification.
• Wrappers provided to simplify Key Generation/Loading, RSA encrypt/decrypt, ECC sign/verify, ECDH, NV, Hashing/HACM, AES, Sealing/Unsealing, Attestation, PCR Extend/Quote and Secure Root of Trust.
• Any TPM 2.0 compliant module is supported. Tested modules include Infineon SLB9670, SLB9672, SLB9673, STMicroelectronics ST33KTPM2XSPI, ST33KTPM2I, ST33TPHF2XSPI, ST33TPHF2XI2C, Microchip ATTPM20, Nations Technologies/NSING Z32H330, NS350, Nuvoton NPCT650, NPCT750, and SealSQ QVault TPM (first TPM with post-quantum ML-DSA/ML-KEM in silicon).
• wolfTPM uses the TPM Interface Specification (TIS) to communicate either over SPI, or using a memory mapped I/O range.
• On Linux, wolfTPM auto-detects between the kernel TPM driver (/dev/tpmX) and direct SPI access at runtime - a simple ./configure && make works with either interface.
• wolfTPM can also use the Linux TPM kernel interface (/dev/tpmX) to talk with any physical TPM on SPI, I2C and even LPC bus.
• Platform support for Raspberry Pi (Linux), MMIO, STM32 with CubeMX, Atmel ASF, Xilinx, QNX, Infineon TriCore, wolfHAL and Barebox.
• The design allows for easy portability to different platforms:
  • Native C code designed for embedded use.
  • Single IO callback for hardware SPI interface.
  • No external dependencies.
  • Compact code size and minimal memory use.
• Includes example code for:
  • Most TPM2 native API's
  • All TPM2 wrapper API's
  • PKCS 7
  • Certificate Signing Request (CSR)
  • TLS Client
  • TLS Server
  • Use of the TPM's Non-volatile memory
  • Attestation (activate and make credential)
  • Benchmarking TPM algorithms and TLS
  • Key Generation (primary, RSA/ECC and symmetric), loading and storing to flash (NV memory)
  • Sealing and Unsealing data with an RSA key or externally signed policy.
  • Time signed or set
  • PCR read/reset
  • GPIO configure, read and write.
  • Endorsement Key/Cert retrieval and validation.
• Parameter encryption support using AES-CFB or XOR.
• Support for salted unbound authenticated sessions.
• Support for HMAC Sessions.
• Support for reading Endorsement certificates (EK Credential Profile).
• Includes a portable firmware TPM 2.0 implementation (fwTPM, also known as fTPM / swtpm) for embedded platforms without a discrete TPM chip. See Firmware TPM (fwTPM / fTPM / swtpm) below.
• Post-quantum cryptography support via TPM 2.0 Library Specification v1.85: ML-DSA (FIPS 204) signing and ML-KEM (FIPS 203) key encapsulation, enabled with --enable-v185 (full v1.85) or the leaner --enable-pqc (ML-DSA / ML-KEM only), with per-operation trimming via --enable-mldsa/--enable-mlkem. Auto-detected when --enable-fwtpm is built against a wolfCrypt that has ML-DSA + ML-KEM. Both the client library and the fwTPM server implement the eight new v1.85 PQC commands. See Post-Quantum Cryptography (v1.85) below.
• SPDM attestation support (DMTF DSP0274) over the TCG SPDM-over-TPM binding, with a TCG certificate handshake and a DSP0274 pre-shared-key (PSK) handshake, enabled with --enable-spdm. The fwTPM server includes an SPDM 1.3 responder so the stack can be exercised end-to-end in CI without discrete silicon. See SPDM Attestation below.

Note: See examples/README.md for details on using the examples.

Firmware TPM (fwTPM / fTPM / swtpm)

wolfTPM includes a portable firmware TPM 2.0 implementation (fwtpm_server) built entirely on wolfCrypt. It provides a standards-compliant TPM 2.0 command processor that can replace a hardware TPM on embedded platforms without a discrete TPM chip, or serve as a drop-in development and CI/CD replacement for external simulators like swtpm or the Microsoft TPM simulator.

Features:

• 105 TPM 2.0 commands implemented (93% of v1.38 spec) with wolfCrypt cryptography (RSA, ECC, SHA, AES, HMAC)
• Socket transport (Microsoft TPM simulator protocol) compatible with tpm2-tools and wolfTPM examples
• TIS register-level transport over shared memory or SPI/I2C for bare-metal integration
• HAL abstractions for IO transport and NV storage portability
• File-based or custom NV storage via HAL callbacks
• Compile-time algorithm and per-command-group feature selection (e.g., NO_RSA, FWTPM_NO_NV, and independent per-command-group gates you pick and choose to shrink the fTPM footprint)
• WOLFTPM_SMALL_STACK support for constrained environments

See docs/FWTPM.md for build instructions, configuration, and API reference.

Post-Quantum Cryptography (v1.85)

wolfTPM implements the post-quantum algorithms added in TCG TPM 2.0 Library Specification v1.85, built on wolfCrypt's FIPS 203 (ML-KEM) and FIPS 204 (ML-DSA) modules.

Supported algorithms:

wolfTPM officially supports the SealSQ QVault TPM, the first shipping TPM 2.0 with these v1.85 PQC algorithms in silicon. Build for it with --enable-sealsq --enable-pqc. The same examples and wrapper API also run against the in-tree fwTPM server for CI or when no hardware is present. See the TPM2 Benchmarks section for measured ML-DSA / ML-KEM performance on the QVault TPM.

Building

wolfSSL (ML-DSA and ML-KEM in wolfCrypt):

./configure --enable-wolftpm --enable-pkcallbacks --enable-keygen \
            --enable-mldsa --enable-mlkem \
            --enable-harden CFLAGS="-DWC_RSA_NO_PADDING"
make
sudo make install

wolfTPM:

./configure --enable-fwtpm --enable-pqc
make

--enable-v185 turns on the full v1.85 build (WOLFTPM_V185): the PQC algorithms plus the non-PQC v1.85 spec additions. --enable-pqc turns on just the lean PQC subset (WOLFTPM_PQC) — ML-DSA / ML-KEM only — which is smaller for deployments that do not need the rest of v1.85. If you omit both but --enable-fwtpm is set and wolfCrypt has ML-DSA + ML-KEM available, configure auto-detects and enables full v1.85. Pass --disable-pqc to opt out explicitly.

Trimming the PQC footprint

To compile only the operations you call (smaller binary, no malloc needed), mirror the wolfSSL flags:

# ML-DSA verify-only + ML-KEM encapsulate-only (no sign, no decapsulate)
./configure --enable-pqc --enable-mldsa=verify-only --enable-mlkem=enc

These map to WOLFTPM_NO_MLDSA_SIGN, WOLFTPM_NO_MLKEM_DECAP, etc., which embedded integrators can also pass directly via CFLAGS without autotools. Existing --enable-v185 builds are unaffected (every operation defaults on). Disabling both algorithms (--enable-mldsa=no --enable-mlkem=no) is a configure error — use --disable-pqc to build without any post-quantum support.

The same flags also trim the fwTPM server: --enable-fwtpm --enable-mldsa=verify-only builds a server that implements only ML-DSA verify (the sign command handlers, dispatch entries, and crypto are compiled out). fwTPM always builds the full v1.85 spec surface, so the trims apply on top of WOLFTPM_V185.

Running the examples

make check

See examples/pqc/README.md for per-example details — the pqc_ctrl control center (every PQC operation plus board control in one CLI, with pqc_ctrl.sh running the full command set), pqc_mssim_e2e, mlkem_encap, and PQC options on the general-purpose keygen/keyload tools (-mldsa, -hash_mldsa, -mlkem).

For the fwTPM server's PQC internals — the eight v1.85 commands, primary-key derivation, buffer constants, and spec-interpretation decisions — see docs/FWTPM.md.

SPDM Attestation

wolfTPM implements SPDM (Security Protocol and Data Model, DMTF DSP0274) for TPM 2.0 attestation over the TCG SPDM-over-TPM binding. Both the TCG certificate handshake and the DSP0274 pre-shared-key (PSK) handshake are supported, negotiating SPDM protocol version 1.3.

For testing without discrete silicon, the fwtpm_server ships an SPDM 1.3 responder that drives the same handshake the real Nuvoton and Nations parts use, so the SPDM stack can be exercised end-to-end in CI.

Build with --enable-spdm plus at least one handshake mode (--enable-tcg for the certificate handshake, --enable-psk for the PSK handshake). Vendor wire-format adapters are optional (--enable-nuvoton, --enable-nations).

See src/spdm/README.md and src/fwtpm/README.md for build instructions, responder modes, and the end-to-end test scripts.

TPM 2.0 Overview

Hierarchies

Platform    TPM_RH_PLATFORM
Owner       TPM_RH_OWNER
Endorsement TPM_RH_ENDORSEMENT

Each hierarchy has their own manufacture generated seed.

The arguments used on TPM2_Create or TPM2_CreatePrimary create a template, which is fed into a KDF to produce the same key based hierarchy used. The key generated is the same each time; even after reboot. The generation of a new RSA 2048 bit key takes about 15 seconds. Typically these are created and then stored in NV using TPM2_EvictControl. Each TPM generates their own keys uniquely based on the seed.

There is also an Ephemeral hierarchy (TPM_RH_NULL), which can be used to create ephemeral keys.

Platform Configuration Registers (PCRs)

Contains hash digests for SHA-1 and SHA-256 with an index 0-23. These hash digests can be extended to prove the integrity of a boot sequence (secure boot).

Terminology

This project uses the terms append vs. marshall and parse vs. unmarshall.

Acronyms:

• HAL: Hardware Abstraction Layer.
• NV: Non-Volatile memory.
• TPM: Trusted Platform Module.

Platform

The examples in this library are written for use on a Raspberry Pi and use the spi_dev interface.

IO Callback (HAL)

See the HAL manual in hal/README.md.

For interfacing to your hardware interface (SPI/I2C) a single HAL callback is used and configuration on initialization when calling TPM2_Init or wolfTPM2_Init.

There are HAL examples in hal directory for:

• Atmel ASF
• BareBox
• Espressif ESP-IDF
• Infineon TriCore
• Linux
• STM32 CubeMX
• wolfHAL
• Xilinx

We also support an advanced IO option (--enable-advio/WOLFTPM_ADV_IO), which adds the register and read/write flag as parameter to the IO callback. This is required for I2C support.

Hardware

Tested with:

• Infineon OPTIGA (TM) Trusted Platform Module 2.0 SLB9670, SLB9672 and SLB9673 (I2C).
  • LetsTrust: Vendor for TPM development boards http://letstrust.de.
• STMicro STSAFE-TPM, ST33TPHF2XSPI/2XI2C and ST33KTPM2X (SPI and I2C)
• Microchip ATTPM20 module
• Nuvoton NPCT65X or NPCT75x TPM2.0 modules
• Nations Technologies Z32H330 or NS350 TPM 2.0 modules
• SealSQ QVault TPM 2.0 module (SPI, post-quantum ML-DSA / ML-KEM)
• NVIDIA Jetson Orin (Tegra234) firmware TPM - a TPM 2.0 running as an OP-TEE trusted application, reached through the Linux kernel driver rather than a bus. See docs/DEVTPM.md.

Device Identification

Infineon SLB9670: TPM2: Caps 0x30000697, Did 0x001b, Vid 0x15d1, Rid 0x10 Mfg IFX (1), Vendor SLB9670, Fw 7.85 (4555), FIPS 140-2 1, CC-EAL4 1

Infineon SLB9672: TPM2: Caps 0x30000697, Di