SBSFU configuration AN5056
20/49 AN5056 Rev 8
4 SBSFU configuration
4.1 Features to be configured
X-CUBE-SBSFU supports:
• 2 modes of operation: dual and single slot configurations
• 3 cryptographic schemes using symmetric and asymmetric cryptographic operations
• 2 cryptographic middleware:
– STMicroelectronics middleware: X-CUBE-CRYPTOLIB library integrated into the
1_Image and 2_Images variants.
– Third-party middleware: mbedTLS (Open-source code) cryptographic services.
Examples are provided for the 32L496GDISCOVERY, B-L475E-IOT01A,
32F413HDISCOVERY, 32F769IDISCOVERY, P-NUCLEO-WB55, and NUCLEO-
H753ZI Nucleo boards in the 2_Images_OSC variant.
• STSAFE-A110 secure element used to host X509 certificates and keys. An example is
provided for the B-L4S5I-IOT01A board in the 2_Images_STSAFE variant.
• KMS middleware. An example is provided for the B-L475E-IOT01A and B-L4S5I-
IOT01A boards in the 2_Images_KMS variant.
• External Flash memory with on-the-fly decryption (OTFDEC). An example is provided
for the STM32H7B3I-DK board in the 2_Images_ExtFlash variant using a specific
cryptographic scheme with AES-CTR firmware encryption.
• External Flash memory without on-the-fly decryption (OTFDEC). An example is
provided for the STM32H750B-DK board in the 2_Images_ExtFlash variant. Active
slot, as well as download slot, are mapped in an external Flash memory, thus firmware
confidentiality cannot be ensured.
• External Flash memory without on-the-fly decryption (OTFDEC). An example is
provided for the B-L475E-IOT01A board in the 2_Images_ExtFlash variant. A specific
installation process without swap is selected SFU_NO_SWAP to ensure confidentiality
by keeping the download slot always encrypted.
• External Flash memory without on-the-fly decryption (OTFDEC). An example is
provided for the STM32WB5MM-DK board in the 2_Images_ExtFlash variant.
Download slot, as well as backup slot, is mapped in an external Flash memory. A
specific installation process without swap is selected SFU_NO_SWAP to ensure
confidentiality by keeping both slots always encrypted. More details are provided in the
Appendix H of the user manual Getting started with the X-CUBE-SBSFU STM32Cube
Expansion Package (UM2262).
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