wolfPUF SRAM-Based Device-Unique Key Generation

wolfPUF is a software-based SRAM Physical Unclonable Function (PUF) implementation in wolfCrypt. It generates stable, device-unique 256-bit cryptographic keys from the power-on state of SRAM. The keys are reconstructed with error correction when required instead of being stored in flash or eFuses. Only non-secret data needed for reconstruction remains on the device. wolfPUF requires no secure element, TPM, or vendor-specific PUF hardware.

Almost every connected device holds a secret key to sign firmware, authenticate a TLS session, or encrypt stored data. Keeping that key out of an attacker’s hands is the hard part, and it is not just a small-device problem. Store it in on-chip or external flash and anyone with JTAG, an exposed debug port, or access to the flash bus can read it out. Burn it into eFuses, and it can still be recovered by decapping the die. A secure element or TPM solves this but adds cost, board space, and another supplier to qualify — and many designs, large and small, ship without one. Read the blog to learn more.

One-time enrollment and per-boot key reconstruction
Configurable BCH error-correction profiles
HKDF-SHA256 key derivation with caller-defined labels
SHA-256 device identity generation
Independent keys for different applications from one SRAM fingerprint
Public helper-data generation during enrollment
Key reconstruction using stored helper data
Optional compact helper-data format
SRAM health testing before enrollment and reconstruction
Rejection of invalid or degenerate SRAM readings
Secure key and PUF context zeroization
Designed for MCUs with reservable, uninitialized SRAM
No vendor-specific PUF peripheral required
Bare-metal example for Cortex-M targets
Tested on the ST NUCLEO-H563ZI with STM32H5
Coming soon: Xilinx Zynq-7000
Synthetic SRAM mode for host development and CI testing
Autotools, CMake, and user_settings.h configuration

PRODUCTS

wolfPUF SRAM-Based Device-Unique Key Generation

Highlights

Features