Upper limit on the size of the 'ID Scope' created by a Device Provisioning Service.

Arty29 146 Reputation points
2021-10-06T22:52:19.693+00:00

Hello,

I am setting up a resource constrained IoT device to use a Device Provisioning Service and I am trying to reserve space in the internal flash memory to store the relevant device specific information that will need to be factory installed.

I intend to use Group Enrollment and Symmetric Key attestation so I think that the following information will need to be factory configured on each device:

Registration ID
Device Key
ID Scope

The size of the Registration ID is under my control and as I understand it the key would be at most a Base-64 encoded 64-byte value. What I can’t put a bound on is the ID Scope value which is generated by the provisioning service. Is there a realistic limit to its size, and if so is this documented somewhere?

The only other piece of information that I think the device needs is the provisioning host endpoint, which I intend to hard-code into the firmware. If there is anything else that I have missed I would appreciate someone pointing it out.

Thank you.

Azure IoT Hub
Azure IoT Hub
An Azure service that enables bidirectional communication between internet of things (IoT) devices and applications.
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  1. Sander van de Velde | MVP 31,106 Reputation points MVP
    2021-10-07T09:48:53.217+00:00

    Hello @Arty29 ,

    the registrationID is just a string:

    Registration ID: Enter a registration ID to identify the enrollment. Use only lowercase alphanumeric and dash ('-') characters. For example, symm-key-device-007.  
    

    Because this value is part of the configuration, this would likely resemble the 'public' unique identification of the device (eg. serial number, mac address).

    The ID Scope has a limited length and pattern (just generate one in a DPS and you know the pattern).

    Yes, the provisioning endpoint could be hardcoded. It's eg. already set in the configuration of IoT Edge runtimes too.

    1 person found this answer helpful.

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