Delay and Disruption Tolerant Networks (DTNs) are networks that aim to bring low-cost best-effort connectivity to challenged environments with no or limited infrastructures. Nodes in DTNs are often highly mobile and experieence intermittent connectivity. DTNs can be deployed in developing countries and are poised to play a key part in future space networks.

Example DTN Scenario:
Rural Area Connectivity over Transportation Infrastructures

The key differences between DTN and other networks, e.g., Sensor Networks are:

1. No End To End Path:
   Node mobility creates partitions in the network. We can not assume that there is a complete end to end path between a source and destination. If a path does exist it is assumed to be unstable. Instead, an end to end path exists over time, as nodes move and forward messages to each other.


2. High Message Delays:
   The opportunistic nature of DTNs means messages that are delivered often experience high delays. Delays can are typically on the order of minutes or hours, but could potentially be days depending on the exact scenario.

 In this project, we study techniques for privacy, authenticity and message confidentiality :

• Gene Tsudik - Research Professor
• Karim El Defrawy - Graduate Student Researcher
• John Solis - Graduate Student Researcher

High node mobility and infrequent connectivity inherent to DTNs make it challenging to implement simple and traditional security services, e.g., message integrity and confidentiality. In particular, it is hard to retrieve credentials of peer users/nodes. Also, multi-round security protocols (typically found in handshakes at network and session layers) are greatly handicapped due to long and uneven delays.

This project focuses on the problem of initial secure context establishment in DTNs. We observe that users can take advantage of social information to send secure and confidential messages.

The basic idea is for the source and destination users to use common affiliations that known the public key, or existing shared secret, as interemediaries to securely route messages.

We investigate schemes that enable secure routing for both intra and inter-region routing. We give an informal security analysis and show, by simulation, the probablity of message interception by colluding nodes in the honest-but-curious adversarial model.

We also look at Facebook social networking to show network reachability using our schemes. Full details can be found in the most recent paper version available here.

A sneak peak of our results:

Message Interception Probability for Intra-region Routing Infrastructures

Facebook Network Coverage

Facebook Friends-of-Friends CDF Data

• Leveraging Social Contacts for Message Confidentiality in Delay Tolerant Networks
  Karim El Defrawy, John Solis and Gene Tsudik
  IEEE International Computer Software and Applications Conference(COMPSAC '09) ,
  Seattle, Washington, July 2009.