A delay tolerant network (DTN) is a store and forward network where
end-to-end connectivity is not assumed and where opportunistic links
between nodes are used to transfer data.  An emerging application of
DTNs are rural area DTNs, which provide Internet connectivity to rural
areas in developing regions using conventional transportation mediums,
like buses.  Potential applications of these rural area DTNs are
e-governance, telemedicine and citizen journalism.  Therefore,
security and privacy are critical for DTNs.  Traditional cryptographic
techniques based on PKI-certified public keys assume continuous
network access, which makes these techniques inapplicable to DTNs.  We
present the first anonymous communication solution for DTNs and
introduce a new anonymous authentication protocol as a part of it.
Furthermore, we present a security infrastructure for DTNs to provide
efficient secure communication based on identity-based cryptography.
We show that our solutions have better performance than existing
security infrastructures for DTNs.