Alexandros Fragkiadakis, FORTH-ICS, Greece
Outline Trust management and trust computation Blockchain technology and its characteristics Blockchain use-cases for IoT Smart contracts Blockchain challenges Conclusions 2
Trust management and trust computation are non-trivial issues in an IoT ecosystem for a number of reasons: presence of resource-constrained devices lack of standardisation heterogeneous devices protocol inefficiencies lack of interoperability unattended operating environment, etc. 3
IoT devices perform several specialized operations: monitoring alerting on-demand data provisioning actuating IoT networks for such scenarios are susceptible to various attacks launched by adversaries with various motives 4
Countermeasures against such attacks often include cryptographic means in several layers However, given the broadcast nature of the wireless medium, these means cannot protect against a number of attacks (e.g. routing attacks, etc.) Same problem when nodes intentionally or unintentionally misbehave 5
For tackling these issues, several trust management and computation schemes have been proposed by the research community The main idea is that all nodes observe their neighbors by collecting various information like the packet drop rate, etc. Other works combine physical-layer metrics like the SINR for adjusting observations reliability 6
Trust computation is performed aiming to assign a trust value for each node In general, the trust-based models are classified into three categories: Centralised-> all nodes send their evaluation reports to a single node for report fusion Distributed->each node fuses the individual reports and estimates the reputation of its neighbors Hybrid->network is split into multiple clusters and the elected cluster heads perform fusion 7
Blockchain is used in Bitcoin, the famous cryptocurrency, and consists of a series of interrelated blocks 8
Each block can have several fields, depending on the implementation: Previous hash -> contains the hash value of the previous block List of transactions -> executed within this block (transactions are often organized as a Merkle tree, a binary tree with hash pointers) Nonce -> one-time random value used as one of the hash function arguments Hash value of the block -> computed using as input the data of the block 9
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Blockchain main characteristics Blockchain -> maintained by all nodes in the network Certain rules and means have to exist and respected by all nodes, otherwise chaos will rise: Strong cryptographic means for transaction signing Transactions are propagated in the network only if they are valid Block creation is controlled by explicit mechanisms (e.g. Proof of Work, Proof of Elapsed Time, etc.) H(nonce prev_hash mrkl_root)<target, 11
Blockchain main characteristics Two types of nodes: Simple->issue transactions Miners->create blocks (economic incentives, etc.) Distributed and immutable database (ledger) Public ledger Private ledger Controlled time for mining: Solving a puzzle Waiting for some pre-defined time to elapse 12
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Blockchain use-cases for IoT 14
Blockchain use-cases for IoT Healthcare -> medical data are stored in the blockchain and can be accessed by doctors and insurance companies Smart waste management -> citizens make payments based on the waste they produce Supply chain monitoring -> tracking of products and the conditions they are stored/shipped (e.g. temperature, humidity, etc.) Smart grid monitoring -> household energy consumption and billing operations 15
Smart contracts Smart contract -> a computerized transaction protocol that executes the terms of a contract Smart contracts are scripts stored in the blockchain -> are immutable ->no doubt a contract exists -> no one can refuse he has signed a contract Smart contract examples: Reward xx units when age of information < age_max Switch to solar supply when main supplier s power unit > cost_max 16
Ethereum smart contract example: 17
Blockchain challenges Limits on data storage Slow writes (block generation) Limited bandwidth Endless ledger 18
Blockchain cybersecurity challenges Cryptography (Key management) Privacy Software bugs Consensus hijack (>51% of malicious users, Quantum computing) Distributed DoS (e.g. roque wallets that send fake transactions) Interoperability 19
Conclusions IoT devices perform several specialized operations IoT networks are susceptible to a number of attacks Current trust-based systems used, have several inefficiencies Blockchain technology enables interactions in trust-less environments Certain rules and schemes have to exist to make blockchain technology feasible 20
Thank you! 21