Towards an optimized BlockChain for IoT Ali Dorri*#, Salil Kanhere*#, Raja Jurdak#* *University of New South Wales #CSIRO Data61

IoT security and privacy is challenging DDOS attack on DNS IoT security and privacy is challenging DDOS attack in the US in 2016. Simple IoT devices were compromised and used to launch a large DDOS attack by flooding DNS service provider called Dyn coming from "tens of millions of IP addresses at the same time. 2 hours downtime Source: Downdetector.com. Optimised BlockChain for IoT | Raja Jurdak

Possible Solution Optimised BlockChain for IoT | Raja Jurdak

BlockChain Overview A distributed immutable time-stamped ledger Creates a secure network over untrusted users Changeable PKs as users identity introduce high level privacy Demands for solving a puzzle to append blocks to the BlockChain (mining) Optimised BlockChain for IoT | Raja Jurdak

BlockChain challenges in IoT Resource Consuming Resource-constrained devices Block mining is time consuming Demands low latency Scales poorly with network size Very large scale Bandwidth-inefficient Limited bandwidth and energy resource Poor scaling due to fully distributed nature Optimised BlockChain for IoT | Raja Jurdak 4

Optimising the BlockChain for IoT Hierarchical structure Private centralized BlockChain at local level Public distributed BlockChain at overlay Clustered overlay topology - limited nodes process BlockChain Optimised BlockChain for IoT | Raja Jurdak

IoT BlockChain Features Separate data and transactions flow - decreased delay Distributed trust between CHs – reduced processing Optimised BlockChain for IoT | Raja Jurdak

Local Immutable Ledger Smart Home Local Immutable Ledger LBM Smart home devices are managed centrally by the home manager Devices can share data with each other or the cloud storage when they receive permission from the owner LBM manages a local immutable ledger that has transactions and policy header. Policy is used by the home owner to enable user to have control over the smart home communications Uses DHsymmetric encryption for efficiency Optimised BlockChain for IoT | Raja Jurdak

Transactions handling CHs Request data Forwarding Authorization Transaction to be stored Request data Request device data Request data Request data note separation of data and transaction flow CHs exchange blocks and cross-verify blocks from others Establish consistency and distributed trust to reduce proportion of verified blocks from trusted sources Optimised BlockChain for IoT | Raja Jurdak

Comparison with Bitcoin Blockchain Feature Bitcoin BlockChain Immutable Ledger Public BlockChain Mining requirement POW None Forking Not allowed Allowed Double spending Not acceptable Not applicable Encryption Asymmetric Symmetric BlockChain visibility Public Private Transaction dissemination Broadcast Unicast Unicast/Multicast Distributed verification All Some Optimised BlockChain for IoT | Raja Jurdak

Performance evaluation – Processing Simulations using NS3 to study the trust method - 50 nodes of which 13 are CHs Optimised BlockChain for IoT | Raja Jurdak

Evaluation - Accessibility threats DDOS attack Devices are not directly accessible Home manager controls all incoming and outgoing transactions Keylists on CHs Target threshold of received transactions Optimised BlockChain for IoT | Raja Jurdak

Accessibility threats Dropping attack Optimised BlockChain for IoT | Raja Jurdak

Accessibility threats Dropping attack Elect new cluster head Optimised BlockChain for IoT | Raja Jurdak

Accessibility threats Dropping attack Appending attack Elect new cluster head False block False block Inject fake transactions in a block Optimised BlockChain for IoT | Raja Jurdak

Accessibility threats Dropping attack Appending attack Elect new cluster head Detected by other CHs False block False block Detected by other cluster heads Graceful degradation with proportion of compromised CHs Optimised BlockChain for IoT | Raja Jurdak

Summary Optimised blockchain for IoT Main features Future directions Maintains security/privacy benefits of classic BC Significantly reduces classic BC overhead Main features Two blockchain tiers Separate data and transaction flow Remove proof-of-work Introduce distributed trust Future directions More extensive performance evaluations Mobile scenarios Optimised BlockChain for IoT | Raja Jurdak

Thank you Raja Jurdak, PhD Senior Principal Research Scientist & Research Group Leader, Distributed Sensing Systems Cyberphysical Systems Program t +61 7 3327 4355 e raja.jurdak@csiro.au w http://research.csiro.au/dss