By supporting wireless applications that can operate with ultra-low power consumption, Bluetooth Low Energy (BLE) opens up a number of new application opportunities for designers – particularly when it is combined with the benefits of NFC technology.
Two areas that are of growing interest are secure, out of band (OoB) pairing and proximity applications based around the concept of BLE IoT systems. Here we look at both of these areas and consider how the latest semiconductor technologies and support tools can be used to simplify their implementation.
Bluetooth Low Energy and Near-Field Communication
Bluetooth low energy (BLE) is the power conserving, application-friendly, incarnation of Bluetooth that was developed for the Internet of Things (IoT). The Bluetooth SIG (special interest group) improved its low power technology launching BT version 4.2 in December 2014. It included additional features such as enhanced data cyphering, support of internet protocol and faster speed compared to v4.1. A further enhancement to the recently announced Bluetooth 5 is expected at end of 2016.
Classic Bluetooth offers advantages such as communication range, ubiquity and low implementation cost. BLE provides significantly lower power consumption. This makes it ideal for the coin cell powered mobile and wearable platforms that dominate the IoT.
Modern devices, such as smartphones, have Bluetooth low energy capability as standard. Increasingly, Near-Field Communication (NFC) is also being added. NFC enables applications such as payment or access control as well as security-related functionality where Bluetooth communications could be intercepted by a malicious third-party. This is the so-called 'Man in the middle' (MITM) scenario.
NFC offers wireless communication, but in a very different way from Bluetooth. Firstly, the distances involved for NFC are up to 100 mm. Secondly, the amount and type of data that can be transferred is limited and highly controlled, depending on the embedded NFC security scheme selections. By contrast, Bluetooth can transfer many kinds of data over distances of up to 100 m.
Out of Band (OoB) delivers secure pairing
Combining the security of NFC and the open communications of Bluetooth brings substantial benefits. Bluetooth incorporates AES-128 encryption, which provides robust resistance to eavesdropping and decryption of intercepted packets. However, both security and ease of use can be improved by taking advantage of Near-Field Communication (NFC) to enhance activities such as pairing.
As NFC requires devices to be in close proximity, it avoids the “man-in-the-middle” issue and prevents unwanted devices connecting without the user’s knowledge or permission. This can be done by transmitting security keys for pairing information, which is called Out-of-Band (OoB) pairing and works within the limited NFC range. NFC pairing is easy and straightforward, and is usually accomplished by bringing the two devices briefly into contact.