  Currently, nearly four billion people live in urban areas. Since this trend
is increasing, natural disasters or terrorist attacks in such areas affect an
increasing number of people. While information and communication technology is
crucial for the operation of urban infrastructures and the well-being of its
inhabitants, current technology is quite vulnerable to disruptions of various
kinds. In future smart cities, a more resilient urban infrastructure is
imperative to handle the increasing number of hazardous situations. We present
a novel resilient communication approach based on smart street lights as part
of the public infrastructure. It supports people in their everyday life and
adapts its functionality to the challenges of emergency situations. Our
approach relies on various environmental sensors and in-situ processing for
automatic situation assessment, and a range of communication mechanisms (e.g.,
public WiFi hotspot functionality and mesh networking) for maintaining a
communication network. Furthermore, resilience is not only achieved based on
infrastructure deployed by a digital city's municipality, but also based on
integrating citizens through software that runs on their mobile devices (e.g.,
smartphones and tablets). Web-based zero-installation and platform-agnostic
apps can switch to device-to-device communication to continue benefiting people
even during a disaster situation. Our approach, featuring a covert channel for
professional responders and the zero-installation app, is evaluated through a
prototype implementation based on a commercially available street light.
