AM2632: appimage.hs could not boot up when enable encryption

ZYT

Part Number: AM2632

Hello, I'm verifing secure boot of AM263x.

Now I have done OTP write and transfer device type to HS-SE on AM263X-CC. And can also boot up sbl_qspi.release.hs.tiimage and hsm_getversion_system.release.appimage.hs (without encryption) successfully.

But when I add compile param "ENC_ENABLED=yes" for hsm_getversion_system, the firmware appimage.hs could not boot up, print log as "[HSM_CLIENT] Proc_Auth_Boot request NACKed by HSM server".

The SDK I'm using is mcu_plus_sdk_am263x_09_00_00_13, and generate hsmRtImg.h with tifs_am263x_08_06_00_05 follow by document.

So What might be the problem?

over 1 year ago

0 Anand Mahadevan SS over 1 year ago

TI__Expert 8165 points

Hi,

What keys are you using for encryption here?

Regards,
Anand Mahadevan SS

0 ZYT over 1 year ago in reply to Anand Mahadevan SS

Prodigy 90 points

I use the default dummy key in SDK, mcu_custMpk.pem/mcu_custMek.key,did not do any modification.

0 Anand Mahadevan SS over 1 year ago in reply to ZYT

TI__Expert 8165 points

Hi ZYT,

I will ask a TIFS expert to look into this. Are you sure the hsmRtImg is generated correctly for the HS-SE case?

Regards,
Anand Mahadevan SS

0 ZYT over 1 year ago in reply to Anand Mahadevan SS

Prodigy 90 points

Yes, I'm sure.
I think the reason is for the limitation: https://software-dl.ti.com/mcu-plus-sdk/esd/AM263X/latest/exports/docs/api_guide_am263x/SECURE_BOOT.html#autotoc_md411

And I want to know whether TI will fix this issue in next version?

0 Anand Mahadevan SS over 1 year ago in reply to ZYT

TI__Expert 8165 points

Hi ZYT,

Apologies that I missed the SBL QSPI part. Encryption is supported in other bootloaders like UART. No, this is not a software limitation which we can overcome. Encryption is not supported from flash because the flash memory is not volatile. If say power goes off after the decryption in place in flash, then the plaintext data is readable from the flash. Alternative would be to declare scratch memory in SRAM, copy the image from flash to the buffer and then authenticate and decrypt from SRAM. But this is highly application specific and we can't assume the scratch buffer space always, especially for SBL QSPI. You could go for this approach if required, or use SBL UART. But direct decryption from flash is not something we can do at the moment.

Regards,
Anand Mahadevan SS

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AM2632: appimage.hs could not boot up when enable encryption