  The Internet-of-Things (IoT) is an emerging and cognitive technology which
connects a massive number of smart physical devices with virtual objects
operating in diverse platforms through the internet. IoT is increasingly being
implemented in distributed settings, making footprints in almost every sector
of our life. Unfortunately, for healthcare systems, the entities connected to
the IoT networks are exposed to an unprecedented level of security threats.
Relying on a huge volume of sensitive and personal data, IoT healthcare systems
are facing unique challenges in protecting data security and privacy. Although
blockchain has posed to be the solution in this scenario thanks to its inherent
distributed ledger technology (DLT), it suffers from major setbacks of
increasing storage and computation requirements with the network size. This
paper proposes a holochain-based security and privacy-preserving framework for
IoT healthcare systems that overcomes these challenges and is particularly
suited for resource constrained IoT scenarios. The performance and thorough
security analyses demonstrate that a holochain-based IoT healthcare system is
significantly better compared to blockchain and other existing systems.
