Modem UUID construction

[Elio Maisonneuve]

Hello,

We are using the Hardware ID with the connect SDK to identify our nRF9160 boards. We have the following configuration in our project:

CONFIG_HW_ID_LIBRARY=y
CONFIG_HW_ID_LIBRARY_SOURCE_UUID=y

As such, we get the modem UUID as an identifier wich looks like this: 50415334-3233-45a2-802a-xxxxxxxxxxxx

The 4 indicating this is an UUID_v4. As per RFC, a v4 UUID should be all random bits, except for the bits indicating the version.

From our sample size of around 10 chips, we got UUID starting with 50415334-3233 several times, and others with a different start but also repeated across chips.

How is this UUID constructed ? Is it guaranteed virtually unique (with a statistically very low risk of collision) ? We want to use a subset of that UUID for ease of referencing. Is the end of the UUID completly random and statistically unique ?

Thanks !

[Sigurd]

Hi,

I'm checking with the modem team, and will get back to you when I know more.

[Elio Maisonneuve]

Hello Sigurd, thank you for looking into it!

Where you able to get any information ?

[Sigurd]

Hi!

Yes, the random part of the UUID can be considered statistically unique, it is derived from SHA256 of the device identity public key. The non-random part is some SoC wafer information.