AES CCM: can INPTR = OUTPTR?

RE: AES CCM: can INPTR = OUTPTR?

bjorn-spockeli — Fri, 08 Apr 2016 13:27:32 GMT

If you set the pointers to the same value, output data will overwrite input data, but it may be that the overwriting happens after data is read, but this has not been verified. Judging by your results, this is not a viable option.

I discussed this with our R&D engineers and this was their reply:

For Tx, Radio PACKETPTR should point to where OUTPTR (encrypted packet) points to. INPTR (clear text) should point to a different location.

For Rx, INPTR should point to where Radio PACKETPTR points to. OUTPTR (clear text) should point to a different location.

-Bjørn

RE: AES CCM: can INPTR = OUTPTR?

will — Thu, 07 Apr 2016 15:59:58 GMT

Bjorn:

Thanks! I will do so... BTW I figured out the answer to my question. You CANNOT set INPTR to OUTPTR. I finally got the LL_START_ENC_RSP correctly encrypted with the proper MIC. I had to set INPTR and OUTPTR to different RAM locations. When they were the same the encryption worked but the MIC was incorrect. I would still like verification from your engineers on this one. Maybe I am not doing something else correctly? Anyway, as I move along I will post other questions on a different thread.

RE: AES CCM: can INPTR = OUTPTR?

bjorn-spockeli — Thu, 07 Apr 2016 07:33:41 GMT

No problem! Please post them in separate questions.

RE: AES CCM: can INPTR = OUTPTR?

will — Wed, 06 Apr 2016 16:52:26 GMT

Thanks Bjorn. I am having issues getting all this working and I may have quite a few more questions if I cant get it working. Should I post them as separate questions to the forum or just add them to this post?

RE: AES CCM: can INPTR = OUTPTR?

bjorn-spockeli — Wed, 06 Apr 2016 11:46:22 GMT

@wes3:(will) I have forwarded this to the R&D guys and will update you as soon as they come back to me.

RE: AES CCM: can INPTR = OUTPTR?

will — Mon, 04 Apr 2016 15:01:32 GMT

Shoot! I thought I put that in there. I am using the nrf52. I am not using the SDK nor softdevice (writing my own BLE controller code). I will also be porting this code to the nrf51 so if there are any differences I would appreciate it if you pointed those out (I have not read the nrf51 docs yet). Thanks!

RE: AES CCM: can INPTR = OUTPTR?

bjorn-spockeli — Mon, 04 Apr 2016 14:29:12 GMT

Which chip, SDK and SoftDevice are you using?