[nRF Connect SDK] Make ble connectable only for multiple paired(bonded) devices

Question

Target nRF52832(nrf52dk_nrf52832) SDK NCS v1.9.1 
 Base source 1. C:\Users\user
cs\v1.9.1
rf\samples\bluetooth\peripheral_hids_keyboard 2. C:\Users\user
cs\v1.9.1
rf\samples\bluetooth\peripheral_uart 
 My project require two mode(HID and NUS). I made new project that support two mode.(User can select mode, and each mode will begin at boot time). 
 ----------------------------------------------------------------------------------------------------- My project used BT classic. So it can be acceptable for incoming connection regarding paired(bonded) device without discoverable option. BLE protocol as peripheral role does not allow to accept incoming connection without advertise. My question is following scenario is possible. 
 1. Make bonding with serveral other devices(Android, iOS or Windows). (CONFIG_BT_MAX_PAIRED=4) 2. Reboot BLE device(nordic) 3. BLE begin to advertise only for paired devices. (I found we could add paired list into advertise information) 4. Keep advertise until one of paired devices try to connect. 5. Accept incoming connection. 6. If BLE disconnected, BLE begin to advertise again. (Only for paired) 7. If BLE want to pair another device, BLE stop advertise and begin to advertise without paired list. 8. Make pairing for new device. 
 My customer use several our BLE product at the same time, so please review if my scenario is possible. Thanks.

Edvin · Accepted Answer

I think I was a bit confused about your sentence: 
 Tim Hwang said: No bonding device can FIND BLE but cannot connect to it. (As I told you, I'm not expecting no bonding device cannot find BLE) 
 
 I thought this meant that you had the expected behavior. 
 It is still possible to see advertisements even when you are using a whitelist. Advertisements are not encrypted or "invisible" for unbonded devices, as they use the same protocol and the same channels as the devices that are not bonded/using whitelist. The difference is that you will not be able to connect to a device that claims to be using whitelist if you are not on that whitelist. The whitelist itself is not broadcasted, so the bonded device will have to know whether or not it already knows the advertising device or not. 
 So the normal way to claim that you are using a whitelist is to disable the "General discoverable mode" flag, indicating that it is not a discoverable device. So if you don't know the device, you will not be able to connect to it. 
 Yes, you can still see the device if you scan using nRF Connect for Android/iOS, but remember that this is a BLE developer tool, intended to display everything that it can find on the air. Typically in an custom application, you will filter out the devices with this flag set to false, if they are not bonded to that device. And typically, you would also filter on more things, such as an UUID or something. When you think of it, you will see a different selection of BLE devices if you are using a product's custom application than if you are using e.g. the phone's Settings -> Bluetooth tab. 
 
 So if your question is whether it is possible to be completely hidden for unknown devices, then the answer is no. Whatever you set in your advertisement is public information, and even if there was an option to hide everything, I could still sniff the data using a bluetooth sniffer. Try this by turning on a BLE keyboard or mouse without the computer that it is bonded with being turned on. You will see those advertisements on nRF Connect for Android/iOS/Desktop, or using a BLE sniffer. 
 
 But when you use a whitelist, I will not be able to connect to that device, unless I am already on the whitelist, because the peripheral in that case is able to refuse connection requests from unknown devices. 
 
 Best regards, 
 Edvin

[nRF Connect SDK] Make ble connectable only for multiple paired(bonded) devices

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