Near Sound Data Transfer (NSDT) is a sound-based mobile transaction technology developed and patented by Tagattitude since 2005. NSDT uses a one time password sent through the audio channel of a mobile device to create an electronic signature enabling secure transactions. Because all mobile devices have an audio channel (speaker and microphone) built in this technology is compatible with all mobile phones in use worldwide.
Applications
Today, NSDT is primarily used for mobile banking transactions through the mobile money platform Tagpay. It is also used to securely open doors and enable authentication on websites.
References
Near sound data transfer Wikipedia(Text) CC BY-SA