AES CCM encryption by S132 timeslot API

[ALE]

Hi,

I have posted the same question in the following URL. devzone.nordicsemi.com/.../

It will be very helpful if you tell me how to get a correct MIC result by AES CCM mode encryption of nRF52832.

I send you my sample(blinky_ccm.zip). I'm using IAR. Please put files in the following path. (/nRF5_SDK_13.1.0_7ca7556/examples/peripheral)

This sample outputs encryped data every 10 seconds to PC using UART.

The output is as follows.

:INFO:CCM Control Structure
:INFO:
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01  ................
00 00 00 00 00 00 00 00 00 02 02 02 02 02 02 02  ................
02 00 00 00 00 00 00 00                          ........
APP:INFO:Plain text
APP:INFO:
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F  ................
APP:INFO:Encrypt text
APP:INFO:
0D AF 4B 8E 52 50 3A 6E 91 F4 D8 34 26 9B 4E 74  ..K.RP:n...4&.Nt
6D DA 11 AD                                      m...
APP:INFO:

MIC of nrf52832 is "6D DA 11 AD". However, if AES-CCM mode is executed correctly, I suppose that MIC is "D5 6E B7 75". Please let me know if there are any mistakes.

Thank you in advance. blinky_ccm.zip

[run_ar]

As far as I can see you call ccm_crypt_pair_request_prepare every time the timer fires. Could you try to call this only once?

[ALE]

Thank you for your comment. I have tried to call ccm_crypt_pair_request_prepare() for only one time after the first timeout. But it doesn`t work. We still cannot obtain the expected MIC . I have also tried to call ccm_crypt_pair_request_prepare() for only one time in the main(). And the MIC is also wrong. Could you provide a sample so that I can get the expected MIC?

[run_ar]

What are you actually trying to do here? Calling ccm_crypt_pair_request_prepare doesn't actually do anything, it only generates the pair_request_packet. This needs to be sent to the peer and applied there using the ccm_crypt_pair_request_accept function. Then you can use ccm_crypt_packet_encrypt to encrypt the packet, send it to the peer that can use ccm_crypt_packet_decrypt to un encrypt the packet.