7.6.5.11.2 DRBG Mechanism Functions

The DRBG mechanism uses the HMAC_DRBG algorithms and are available for random generation as soon as the PUF controller is out of the Uninitialized or BIST state.

Seed material for DRBG 1:

  • Entropy input (2048 bytes) from PUF SRAM, first compressed to 512 bits
  • Nonce input: 8192 bits (1024 bytes) from PUF SRAM, first compressed to 256 bits
  • Personalization string: 256 bits, product-specific value

Seed material for DRBG 2:

  • Entropy input: 256 bits (32 bytes) from DRBG 1
  • Nonce input: 128 bits (16 bytes) from DRBG 1
  • Personalization string: 256 bits, product-specific value

The inputs of the DRBG2 reseed mechanism (DRNG1 cannot be reseeded) are:

  • 384 bits (48 bytes) from DRBG 1
  • up to 1024 bits (128 bytes) via PUF_DIR (when enabled)

Zeroize operation disables the DRNGs.