nRF91 questions about credentials

[PopradiArpad]

Hi,

I have two nRF9160DKs and I noticed that the SHA-256 digest of the credentials looks very strange

Questions:

1, Why are the digest so repeating? I have installed the JSON credentials got from nRF Cloud without error.

The software is firmware/images_full/nrf9160dk_at_client_2020-04-29_bc7ade8b.hex and mfwnrf916012.zip.

2, During my tests I deleted the first credential with sec_tag 0 from device with image 1.
The device seen on image 2 has that credential. How can I set back that credential?

3, On image 2: what is that credential with sec_tag 0 anyway?
It has type 6 but according to nrf91_at_commandsv1.2.pdf "4.28 Credential storage management %CMNG"
there are types only 0-5.

With kind regards,

Árpád

With kind regards,

Árpád

[Martin Lesund]

Hi Árpád,

Please make sure that you are running the latest MFW: https://www.nordicsemi.com/Products/Low-power-cellular-IoT/nRF9160/Download#infotabs

e.g. 

This can be read out by AT+CGMR

(mfw 1.2.1 is not yet public)

These certificates are stored in the modem flash, so changing the application .hex does not change the certificates.

Please read the examples down in the doc: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fref_at_commands%2FREF%2Fat_commands%2Fmob_termination_ctrl_status%2Fcmng_set.html&cp=2_1_3_27_0

on how you can read out the specific certificates.

When you list the certificates it will look different compared to when you actually read them out.

[PopradiArpad]

Hi Martin,

I use

AT+CGMR

mfw_nrf9160_1.2.0

the latest firmware.

Do you have answers for the questions?

Regards,

Árpád

[Martin Lesund]

1.

Response syntax for read operation:

%CMNG: <sec_tag>,<type>[,<sha>[,<content>]]

It is the SHA that has this "repeating" data.

2.

Once you delete a credential it is gone.

To write the credential again you could use the command:

The following command example writes the client certificate:

AT%CMNG=0,567890,1,"
-----BEGIN CERTIFICATE-----
MIIBc464...
...bW9aAa4
-----END CERTIFICATE-----”
OK

Or you can use the "Certificate Manager" in LTE Link Monitor, just by dragging and dropping the .json file e.g. gathered from nRF Cloud. (example)

3.
I will check internally why an un-specified type can be shown. 

I managed to write to that unspecified type as well:

For now please only use the specified Types

[PopradiArpad]

Hi Martin,

thank you for your answer. This strange repeating digests are even at you so it can not do harm :)

I am new to LTE and nRF9160 and accordingly paranoid :)

This credential with the unspecified 6-er tag is some trash? Or used internally?

Is it ok to delete it?

Regards,

Árpád

[Kenneth]

Looks like the "the unspecified 6-er" is not used for anything at the moment, but it may used in future, so I suggest to leave it untouched.

Best regards,
Kenneth