  Bluetooth Low Energy (BLE) devices have become very popular because of their
Low energy consumption and hence a prolonged battery life. They are being used
in smart wearable devices, smart home automation system, beacons and many more
areas. BLE uses pairing mechanisms to achieve a level of peer entity
authentication as well as encryption. Although, there are a set of pairing
mechanisms available but BLE devices having no keyboard or display mechanism
(and hence using the Just Works pairing) are still vulnerable. In this paper,
we propose and implement, a light-weight digital certificate based
authentication mechanism for the BLE devices making use of Just Works model.
The proposed model is an add-on to the already existing pairing mechanism and
therefore can be easily incorporated in the existing BLE stack. To counter the
existing Man-in-The-Middle attack scenario in Just Works pairing (device
spoofing), our proposed model allows the client and peripheral to make use of
the popular Public Key Infrastructure (PKI) to establish peer entity
authentication and a secure cryptographic tunnel for communication. We have
also developed a lightweight BLE profiled digital certificate containing the
bare minimum fields required for resource constrained devices, which
significantly reduces the memory (about 90\% reduction) and energy consumption.
We have experimentally evaluated the energy consumption of the device using the
proposed pairing mechanism to demonstrate that the model can be easily deployed
with less changes to the power requirements of the chips. The model has been
formally verified using automatic verification tool for protocol testing.
