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TMS320C6746: Is there any on-chip non-volatile available memory?

David Marcos
Prodigy 165 points

Part Number: TMS320C6746
Other Parts Discussed in Thread: OMAPL138

Hi,

We want to use  TMS320C6746 in a project where we the user will be able to update the firmware. We don't want to distribute the firmware update in any format that could lead to easy disassembly/decompilation. Also, the firmware image would be stored in an external boot memory where anyone with basic tools could extract it and dissasemble/decompile it. As far as I know there's no way to secure the firmware in this scenario without any sort of encryption or obfuscation mechanism that would require information stored inside the DSP chip and not in an external memory. That way any attacker would have to physically tamper with the DSP instead of just capturing external signals.

We're aware of the secure-boot enabled C6748 devices but they cost twice as much as the C6746 which is ideal for our application, but it seems like it doesn't have any internal writable non-volatile memory where we could store an encryption key or similar. Even some OTP bits or efuses would be enough. Is there any mechanism available for that?

  • 0
    TI__Guru**** 161600 points
    Hi,

    I've notified the sw team to elaborate.

    Best Regards,
    Yordan
  • 0
    TI__Guru** 116980 points

    Unfortunately on a GP device since the JTAG interface is open, any kind of obfuscation scheme that you use can be overcome by looking at the application code over the emulator interface. There is no on-chip non-volatile memory on this device that can be used for storing an software encrypted image.

    The only EFUSEs on OMAPL138/C6748 that I am aware of are DIE IDs programmed on the device that are used for internal purposes. The DIE ID is programmed on every C674x sample but is not guaranteed to be cryptographic ally unique. Hence we don`t recommend their use in any obfuscation schemes but we know of users in the C6748/OMAPL138 developer community who have used DIE ID register values to come up with schemes to create a unique identifier and potentially to generate keys that they have used in their products at their own risk.
    Refer: e2e.ti.com/.../284370

    Our recommendation is to use secure parts that have dedicated unique EFUSE HW based keys with JTAG locked down for any use case that requires IP protection.

    Regards
    Rahul