Near Field Communication technologies incorporated in some of the latest smartphones can be used for applications such as contactless payments or data exchange between two devices. Although NFC support has found its way into some apps such as the Commonwealth Bank's Kaching payment system, it's still far from achieving widespread adoption.
One factor in this has been the lack of NFC support even in some leading smartphone models; for example Apple is yet to issue a handset that supports NFC. However, researchers at Microsoft have developed an alternative system that can offer NFC-like capabilities, but without requiring dedicated wireless hardware to make it work.
Instead, their system – which the team at Microsoft Research India, Rajalakshmi Nandakumar, Krishna Kant Chintalapudi, Venkata N. Padmanabhan and Ramarathnam Venkatesan dub 'Dhwani' – uses sound.
Dhwani uses the speaker and microphone on phones to securely exchange data, achieving speeds of up to 2.4Kbps; short of the peak rate of 424Kbps possible with NFC but "sufficient for most existing NFC applications" the researchers write in their paper.
As with NFC, the range of Dhwani is far shorter than Wi-Fi or Bluetooth and will work effectively only over a distance of a few centimetres.
In addition to being software-based and hence not requiring specialised hardware for transfers, the researchers also believe that it is more secure than NFC. The researchers managed to monitor NFC communications from around 20-30cm away, and believe that with a more sophisticated antenna monitoring from distances up to a metre may be possible.
For security Dhwani relies on a 'JamSecure' approach which "uses self-jamming coupled with self-interference cancellation at the receiver" to protect any data transmissions.
Essentially this relies on the receiving device transmitting pseudorandom noise while the transmitting device is sending data. Then this noise can be compensated for by the receiver.
Any eavesdropping device would be able to only listen to a combination of the pseudorandom noise and the (data transmitting) noise from the sending device.
The basis of Dhwani's communication system is an 'Acoustic Software Defined Radio'. The researchers conducted tests in noisy environments and established that 6KHz was the lower limit for the system, below which typical ambient noise would interfere with transmissions.