What causes decryption before receiving?

RE: What causes decryption before receiving?

Torsten Robitzki — Wed, 13 Feb 2019 18:29:25 GMT

Hi Kenneth,

thanks a lot for the response. Encryption seems to work pretty well with this workaround.

best regards,

Torsten

RE: What causes decryption before receiving?

Kenneth — Wed, 13 Feb 2019 17:43:14 GMT

Hi,

I can not find any errata on the CCM module, but there may be some dependencies or sequence of operation that the module requires even though not documented, so I am not terrible surprised if the CCM module must be enabled at the start of the connection event and disabled at the end to work as intended. It's been implemented in specific to fulfill the Bluetooth requirements, and then some assumption may have been made by the designers on usage and test.

Best regards,
Kenneth

RE: What causes decryption before receiving?

Torsten Robitzki — Wed, 13 Feb 2019 11:00:45 GMT

It turns out, that if I disable and enable the NRF_CCM, when setting up the connection event, I do not run into the error above. I've read that sequence in the sources of Zephire (Zephire also resets the NRC_CCM before setting up the transmission).

I wonder now, if this just hides a bug in my implementation, or if this is really required. Could someone from Nordic please be so kind and confirm, that this resetting of the NRF_CCM is required? Is there any errata for this?

best regards,

Torsten