NRF51822 Beacon with Secure Connection

[silex]

Hello, I have enough experience for ARM MCUs but I am newbie to BLE technology. I am thinking of a project about using NRF51822 beacon to unlock door when in range. I am using Keil v5 and PCA10028 devkit. I tried beacon example in SDK, which use indirect advertisement. It works, but not secure. Firstly, i want beacon and my gateway get paired first with 6digit password. After that, beacon must go to sleep mode , then wake up and send its ID for every 4seconds. Because battery life is important. I want your help on this. How can i do this? Which protocol should i use? Are there any example for such application?

Thank you so much.

[Petter Myhre]

So currently you have a nRF51 DK (PCA10028), which is the lock (observer/central device), and a nRF51822 Bluetooth Smart Beacon kit which is a key/beacon (broadcaster/peripheral) device. In your current implementation the central device unlocks when it receives an advertising packet from the peripheral, maybe with a certain RSSI. Now you want to add security, so that unauthenticated devices can't unlock the lock. Is this correct?