Is there a way to disable on-the-fly encryption and decryption?

RE: Is there a way to disable on-the-fly encryption and decryption?

Einar Thorsrud — Tue, 03 Sep 2019 13:28:25 GMT

Ah, I finally get the question. No, that is not possible. The CCM module is not very flexible since it is specifically designed to work with the radio in BLE context. The decryption speed has to be one of the supported datarates.

RE: Is there a way to disable on-the-fly encryption and decryption?

Rohith PN — Tue, 03 Sep 2019 13:08:38 GMT

Yes, I kind of got the idea regarding this.

But, I am not using the on-the-fly decryption method. I am explicitly giving the Encrypted data as Input and waiting for the Decryption to complete and get the decrypted output. So, I would like to know if there is any configuration that can be used to get the decryption done in quickly like in the case of Encryption.

RE: Is there a way to disable on-the-fly encryption and decryption?

Einar Thorsrud — Tue, 03 Sep 2019 13:02:59 GMT

Hi,

This is because since decryption happens on the fly as data flows in, it cannot be faster than the pace of the incoming data. So it is expected and correct that decryption takes 8 times longer when the rate is configured for 125 kbps (S=8) compared to using 1 Mbps. For encryption, it is different, since all data is present from the beginning of the operation.

RE: Is there a way to disable on-the-fly encryption and decryption?

Rohith PN — Tue, 03 Sep 2019 11:50:48 GMT

Encrypting 27byte payload is taking 42us even in LR-C8.

RE: Is there a way to disable on-the-fly encryption and decryption?

Rohith PN — Tue, 03 Sep 2019 11:49:01 GMT

Hi,

Thank you. But I am not using SoftDevice.

The problem I am facing when using the above mentioned method is that, the "EVENTS_ENDCRYPT" is coming after 40us when Encrypting which is fine. But when decrypting "EVENTS_ENDCRYPT" is getting set based on the payload length and the datarate.

For Example, if the payload length is 27bytes, "EVENTS_ENDCRYPT" is getting set after 320us. But the same Event is getting set while Encrypting 27bytes payload after 40us in 1M PHY. The same is coming after 2.32ms for 27byte payload in LR-C8 while decrypting.

I would like to reduce this latency.

RE: Is there a way to disable on-the-fly encryption and decryption?

Einar Thorsrud — Tue, 03 Sep 2019 11:41:35 GMT

Hi,

I see. This is not possible if you are using the SoftDevice (Nordic's BLE stack).

RE: Is there a way to disable on-the-fly encryption and decryption?

Rohith PN — Tue, 03 Sep 2019 09:34:33 GMT

Hi,

Using BLE Protocol.

My question was w.r.t configuring on-the-fly encryption/decryption of the packets. i.e. I would like to feed the input to the CCM engine and get the Encrypted/Decrypted Payload as output instead of configuring the on-the-fly mode where PPI and Shorts are used to get the decrypted payload directly.

RE: Is there a way to disable on-the-fly encryption and decryption?

Einar Thorsrud — Tue, 03 Sep 2019 08:43:45 GMT

Hi,

Can you be more specific? Which protocol are you using (BLE or something else?), and which stack, etc? And do you want to disable encryption/decryption in a non-standard way, for instance for some debugging, or do you just want to not encrypt the link?

For instance with BLE, you do not have to encrypt the link, but depending on the configuration some characteristics may not be usable without it (the required security level is configured separately for each characteristic).