  Communication channel established from a display to a device's camera is
known as visual channel, and it is helpful in securing key exchange protocol.
In this paper, we study how visual channel can be exploited by a network
terminal and mobile device to jointly verify information in an interactive
session, and how such information can be jointly presented in a user-friendly
manner, taking into account that the mobile device can only capture and display
a small region, and the user may only want to authenticate selective
regions-of-interests. Motivated by applications in Kiosk computing and
multi-factor authentication, we consider three security models: (1) the mobile
device is trusted, (2) at most one of the terminal or the mobile device is
dishonest, and (3) both the terminal and device are dishonest but they do not
collude or communicate. We give two protocols and investigate them under the
abovementioned models. We point out a form of replay attack that renders some
other straightforward implementations cumbersome to use. To enhance
user-friendliness, we propose a solution using visual cues embedded into the 2D
barcodes and incorporate the framework of "augmented reality" for easy
verifications through visual inspection. We give a proof-of-concept
implementation to show that our scheme is feasible in practice.
