Mobile users depend heavily on ad-hoc connections for many, if not most, 
of their communication. The need for ad-hoc communication without any 
prior knowledge about the potential communication partners is often seen as 
a security risk and is certainly difficult to tackle, as is evident by the
typical struggles that mobile users face when trying to connect via
established communication technologies like WLAN or Bluetooth.

For widespread use of secure communication in settings where no 
administrator can be expected to configure devices, but where users are 
on their own, more intuitive means of establishing secure channels are
necessary. The security of such a channel usually rests on one seemingly
simple property: authentication. Without proper authentication, one can not 
be sure who it is that the connection is made to. By solving the
authentication problem, secure channels can be constructed easily by using 
one of the well-known standard protocols. Authentication based on context 
common to two or more devices or based on properties of the current 
context promises to make authentication more intuitive and simpler to use.