ST STM32H7 Series Application Note

6.16 Independent watchdog (IWDG)
The IDWG is a free running down counter that can be used to trigger a system reset when the counter reaches a
given timeout value. The IDWG can be used to provide a solution in case of malfunctions or deadlock in running
code. The IDWG is clocked by its own independent low-speed clock (LSI), so that it stays active even in the event
of a main clock failure.
When to use the IWDG
The IWDG can be used to break deadlocks. It can also be used to control execution time of critical code (such as
decryption or flash memory programming).
Note: The IDWG is available on all STM32 devices.
6.17 Device ID
Each STM32 device has a unique 96-bit identifier providing an individual reference for any device in any context.
These bits can never be altered by the user.
The unique device identifier can be used for direct device authentication, or for instance to derive a unique key
from a master OEM key.
6.18 Cryptography
As described in Section 5, cryptography is essential to secure an embedded system. The cryptography enables
confidentiality, integrity, and authentication of data or code. For efficiently supporting these functions, most
STM32 series include products with hardware cryptography peripherals. These peripherals allow cryptographic
computations (such as hashing or symmetric algorithms) to be accelerated. For devices with no such specific
hardware acceleration, the STM32 cryptographic firmware library (CryptoLib) provides a software implementation
of a large set of cryptographic algorithms.
6.18.1 Hardware accelerators
The following cryptographic peripherals are available in STM32 devices:
• TRNG (true random generator)
– hardware-based peripheral providing a physical noise source. Used to feed a DRNG with a seed, or
directly for random numbers, depending on device.
Note: For details about the RNG validation, refer to the application note 'STM32 microcontroller
random number generation validation using the NIST statistical test suite' (AN4230).
• AES accelerator
– encryption/decryption
– 128- or 256‑bit keys
– several modes of operation (such as ECB, CBC, CTR, or GCM)
– DMA support
Note: When the AES is used for encryption or decryption, the access to its registers containing the key
must be protected and cleaned after use (the MPU can be configured to restrict access to memory with
keys).
• PKA accelerator
– acceleration of RSA, DH, and ECC over GF(p) operations, based on the Montgomery method for fast
modular multiplications
– built-in Montgomery domain inward and outward transformation
• HASH accelerator
– MD5, SHA1, SHA224, SHA256
– FIPS compliant (FIPS Pub 180-2)
– DMA support
6.18.2 CryptoLib software library
The STM32 X-CUBE-CRYPTOLIB software library runs on all STM32 devices. It is available for free download at
www.st.com/en/product/x-cube-cryptolib. The version V4 is available with full firmware implementation, compiled
for Cortex‑M0, Cortex‑M0+, Cortex‑M3, Cortex‑M33, Cortex‑M4, and Cortex‑M7.
AN5156
Independent watchdog (IWDG)
AN5156 - Rev 8
page 40/56

ST STM32H7 Series Specifications

General

Brand	ST
Model	STM32H7 Series
Category	Computer Hardware
Language	English