What cause the MIC wrong???

[jimlin]

Hi,

I catched the air data packets by Sniffer and it shown that there was an error, MIC incorrect, which could be seen as followed, and the whole packet was malformed.
I am not clear about this. After the bonding ended successfully, the neccessary data have been stored in the flash, including the encry key. And it could be reloaded when re-start. Is the error happen when flash loading so the encry key was wrong?Or the key was wrong before writting to flash? All the store work are done by the softdevice, right?
It is OK when the slave paired the host at the first time, while the key become wrong once the power off and on again. I guess something happen when restart but not sure what it is.

Please help to give the point out.
Thanks a lot.

[David Edwin]

The sniffer will remember the keys if and only if it was used to sniff the initial bonding process between the 2 devices. You are most likely trying to sniff a connection that was bonded earlier but the sniffer was not used to sniff the connection when the bonding was done.

[jimlin]

So, you mean this is not really wrong about data? As my found, when the slave sends data to the host from the bonding beginning, the interval of two points slave sends is about 8ms. But once restart with bonded, the interval become bigger to 10ms. I assume the key make the interval bigger.

[David Edwin]

I am saying, if you want the sniffer to capture data properly in an encrypted connection, use the sniffer when the devices are getting bonded. This is just how the sniffer works. Data captured without the sniffer getting bonde should not be used in any encryption analysis.