SLUUC54C February 2020 – March 2024 BQ27Z558 , BQ27Z561 , BQ27Z561-R2
The BQ27Z561-R2 uses SHA-256 for authentication.
Detailed information about the SHA-256 algorithm can be found here:
The random number should be a 32-byte random number generated from the host processor system. Once this number is generated, it is used to generate the HMAC value using the random number as the message and the secure key as the secret key for SHA-256.