LESC just work.

[Stayhungry]

Condition 1: LESC = 1, MITM = 1 After successful encryption, p_ble_evt-> gap_evt-> auth_status-> lesc = 1 in BLE_GAP_EVT_AUTH_STATUS

Condition 2: LESC = 1, MITM = 0 (Just Work) After successful encryption, p_ble_evt-> gap_evt-> auth_status-> lesc = 0 in BLE_GAP_EVT_AUTH_STATUS

SDK14.1, S132, may I ask the second case is not LE Secure Connection it? Is this a bug?

[Hung Bui]

Hi,

From my understanding if you do LESC with Just Work, the security level will be considered Mode 1 level 2 which is equal to Legacy Pairing just work. If you want lesc bit = 1 you need level 4 ( MITM).

This is described in section 10.2.1 and 10.2.4 in Vol 3 Part C in Core spec v4.2

A device may be in a Secure Connections Only mode. When in Secure
Connections Only mode only security mode 1 level 4 shall be used

Here we have a similar question.

[Stayhungry]

Thanks. I may understand wrong, I thought 'lesc' means 'LE secure connection', indicating that this is a new feature of BLE4.2, and you mean 'lesc' is not a new feature, but the meaning of Mode 1 level 4,is that right?

[Hung Bui]

Yes I understand LESC is "LE secure connection", it's the new pairing mode in BLE v4.2 . It's a totally new method of pairing compare to Legacy pairing.

However, if it's done using just work mode, the level of security is consider level 2, equal to Legacy Just work. You should use MITM to get to level 4 and that is when the lesc bit can be 1.