Suggest bonding model where central is exposed to public and lacks meaningful IO, the peripheral is private and has good IO, and NFC isn't available

[howard n2wx]

Nordic Semiconductor-ites and fellow forum members have yet to steer me wrong so here we go.

My product has 52832 on both sides. The central and its 21col x 2 row LCD display are publicly viewable and accessible... and irrelevant because I can't touch it.  I can do whatever I want with the '832 on the central but the '832 doesn't own the display: The display is owned by a processor that I can't touch without taking it back through UL so that isn't going to happen.

The other side is a battery powered remote display. As such it's fitted out with a nice 20 char x 4 row LCD panel and three push buttons.  The '832 in the remote owns everything (thank you for the extra horsepower that makes this possible, Nordic).  I'm having a brain fart trying to figure out how to securely bond these devices and restrict characteristic writes to encrypted, MITM-avoided links.  I suppose what I need is a secure procedure.  Note that NFC should be but isn't available.  Thank you in advance from both myself and kitty.

[Sigurd]

Hi,

Without any IO Capabilities on the central side you are limited to "Just Works" bonding. See this link on how the Peer Manager should be configured for that. See this link for a introduction to BLE security.

Relation Between Pairing Methods and I/O capabilities(from BLE spec 4.2 [Vol 3, Part H] page 611):

[howard n2wx]

Thank you. I was afraid that'd be the answer.  I'm going to need to authenticate the peripheral in some other way because the central's physical security can't be assured.  Seems I need to persuade the hardware guys into giving me some i/o on the central, perhaps a physical key lock, so that I can inhibit pairing unless the key is in the lock when the devices are introduced to each other.