Error OOB static key NRF connect

Question

Hi all, 
 I'm using the "ble_app_hrs_paring_nfc" example to setup a static OOB key for pairing with a static longer more secure key. I use this key copied from the example: 
 #define OOB_AUTH_KEY { \
 { \
 0xAA, 0xBB, 0xCC, 0xDD, \
 0xEE, 0xFF, 0x99, 0x88, \
 0x77, 0x66, 0x55, 0x44, \
 0x33, 0x22, 0x11, 0x00 \
 } \
 }
 
 And I added this in the on_ble_evt 
 case BLE_GAP_EVT_AUTH_KEY_REQUEST:
 PRINTF("BLE:	 OOB Key request
");

 err_code = sd_ble_gap_auth_key_reply(p_ble_evt->evt.gap_evt.conn_handle, BLE_GAP_AUTH_KEY_TYPE_OOB, m_oob_auth_key.tk);
 APP_ERROR_CHECK(err_code);
 break;
 
 But when I put in the key "AABBCCDDEEFF99887766554433221100" in the NRF connect screen below it fails and gives this status: 
 "Authentication failed with status BLE_GAP_SEC_STATUS_CONFIRM_VALUE" 
 
 Does anyone know what kind of data the NRF connect expects in this screen? 
 Thanks in advance! 
 Kind regards, 
 Michael

TobiasM · Accepted Answer

Hi Michael, 
 my answer comes a little bit late, but I still ran into the same problem and after some testing and good guesses I've managed to deconstruct the issue here. I was using the nRF Connect v3.3.0 app to connect to the nRF52 DK which was using a hardcoded OOB key. 
 The OOB value for nRF Connect in hex is: h1h2 .. h16|h17 .. h32 (16 byte) 
 The bug causes the software to discard the last 8 bytes h17-h32 and interprets the first 16 hex values as byte values. Also, little endian is applied which leads to the following corresponding TK (again in hex): 
 0x0|h16|0x0|h15|..|0x0|h2|0x0|h1 
 Further is every hex value a-f interpreted as 0 (letters are always 0). Therefore, we can deduce that you cannot input your chosen key. If you take 
 0x05, 0x04, 0x03, 0x02, \ 
 0x01, 0x00, 0x09, 0x08, \ 
 0x07, 0x06, 0x05, 0x04, \ 
 0x03, 0x02, 0x01, 0x00 
 instead (note that for the TK you need change the little endian format again), the corresponding OOB key in the Connect app would be 5432109876543210|0 .. 0 but in fact the 0 .. 0 string can be any value. 
 I hope this will help everyone who is struggling at this point and hopefully this will get fixed soon, after already 3 years. 
 Best regards 
 Tobias Moser

Error OOB static key NRF connect

Top Replies