Citation: Kluss, B.; Rashidibajgan, S.;
Hupperich, T. Blossom: Cluster-Based
Routing for Preserving Privacy in
Opportunistic Networks. J. Sens.
Actuator Netw. 2022, 11, 75.
https://doi.org/10.3390/
jsan11040075
Academic Editor: Antonio Celesti
Received: 14 September 2022
Accepted: 10 November 2022
Published: 16 November 2022
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Journal of
Actuator Networks
Sensor and
Article
Blossom: Cluster-Based Routing for Preserving Privacy in
Opportunistic Networks
Benedikt Kluss , Samaneh Rashidibajgan * and Thomas Hupperich
Department of Information Systems, University of Münster, 48149 Münster, Germany
* Correspondence: samaneh.rashidibajgan@wi.uni-muenster.de
Abstract:
Opportunistic networks are an enabler technology for typologies without centralized
infrastructure. Portable devices, such as wearable and embedded mobile systems, send relay messages
to the communication range devices. One of the most critical challenges is to find the optimal route
in these networks while at the same time preserving privacy for the participants of the network.
Addressing this challenge, we presented a novel routing algorithm based on device clusters, reducing
the overall message load and increasing network performance. At the same time, possibly identifying
information of network nodes is eliminated by cloaking to meet privacy requirements. We evaluated
our routing algorithm in terms of efficiency and privacy in opportunistic networks of traditional and
structured cities, i.e., Venice and San Francisco by comparing our approach against the PRoPHET,
First Contact, and Epidemic routing algorithms. In the San Francisco and Venice scenarios, Blossom
improves messages delivery probability and outperforms PRoPHET, First Contact, and Epidemic by
46%, 100%, and 160% and by 67%, 78%, and 204%, respectively. In addition, the dropped messages
probability in Blossom decreased 83% compared to PRoPHET and Epidemic in San Francisco and
91% compared to PRoPHET and Epidemic in Venice. Due to the small number of messages generated,
the network overhead in this algorithm is close to zero. The network overhead can be significantly
reduced by clustering while maintaining a reliable message delivery.
Keywords: opportunistic network; privacy-preserving routing; cluster-based routing; cloaking
1. Introduction
In recent years, smart and wearable devices have rapidly developed to gain higher
processing power and storage space. In combination with the establishment of the Internet
of Things (IoT) paradigm [1], the Internet of Wearable Things (IoWT) emerged [2].
Picture the concept of smart cities with numerous entities, including homes, vehicles,
buildings, wearables, air stations monitoring, etc. These entities, utilized in various fields
of applications such as healthcare, environmental, automation, industrial, and emergency
care, have attracted millions of mobile, i.e., vehicles, smartphones, wearables, and portable
devices and nonmobile, e.g., home and buildings, nodes spreading over the cities capable
of data transition [
3
,
4
]. These nodes are equipped with telecommunication senders and
receivers, connecting via short-range, e.g., Bluetooth, and long-range communication,
e.g., Wi-Fi, and exchanging data to shape the network [5].
Due to their high popularity and degree of mobility, wearable devices are carried
by individuals in daily routine activities, utilizing them as the nodes of a network for
transmitting and exchanging data.
As an IoT enabler technology, opportunistic networks support a decentralized infras-
tructure and, therefore, are suitable for connecting such devices [
3
,
6
–
8
]. Opportunistic
networks (OppNets) take advantage of the mobility of the nodes as well as the social
communication network of individuals who carry these nodes to exchange messages [9].
J. Sens. Actuator Netw. 2022, 11, 75. https://doi.org/10.3390/jsan11040075 https://www.mdpi.com/journal/jsan
