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Blockchain for Internet of Things: A Survey
Hong-Ning Dai, Zibin Zheng, Yan Zhang
TL;DR
IoT’s heterogeneity, decentralization, and resource constraints create interoperability, privacy, security, and data-management challenges. The paper surveys Blockchain of Things (BCoT), including its architecture, smart-contract lifecycle, applications, and 5G-beyond issues. It concludes that BCoT offers benefits including reduced reliance on trusted third parties, improved security, traceability, authenticity verification, and privacy preservation.
Problem
IoT faces interoperability, privacy, security, and data-management challenges, while conventional approaches are difficult to apply in resource-constrained and distributed IoT environments.
Method
The paper provides a comprehensive survey of BCoT, covering blockchain and IoT foundations, architecture, smart contracts, applications, and research issues.
Results
The survey identifies BCoT benefits including reduced trusted-third-party costs, security assurance, data traceability, data-authenticity verification, and privacy preservation.
Takeaways & Limitations
BCoT is presented as a synthesis that can support IoT through blockchain-based interoperability, traceability, reliability, and autonomous interactions.
Abstract
from arXiv · showhide
Internet of Things (IoT) is reshaping the incumbent industry to smart industry featured with data-driven decision-making. However, intrinsic features of IoT result in a number of challenges such as decentralization, poor interoperability, privacy and security vulnerabilities. Blockchain technology brings the opportunities in addressing the challenges of IoT. In this paper, we investigate the integration of blockchain technology with IoT. We name such synthesis of blockchain and IoT as Blockchain of Things (BCoT). This paper presents an in-depth survey of BCoT and discusses the insights of this new paradigm. In particular, we first briefly introduce IoT and discuss the challenges of IoT. Then we give an overview of blockchain technology. We next concentrate on introducing the convergence of blockchain and IoT and presenting the proposal of BCoT architecture. We further discuss the issues about using blockchain for 5G beyond in IoT as well as industrial applications of BCoT. Finally, we outline the open research directions in this promising area.
I. INTRODUCTION
The paper proposes Blockchain of Things (BCoT), integrating blockchain with IoT to address interoperability, traceability, reliability, and autonomous interaction challenges. It surveys prior work, presents a BCoT architecture, examines applications and 5G-beyond issues, and identifies open research directions.
- BCoT integrates blockchain and IoT to improve interoperability, privacy, security, reliability, and scalability.
- A blockchain-composite layer over an overlay P2P network provides uniform access across IoT systems, supporting interoperability across devices, systems, and sectors.
- Blockchain timestamps enable tracing and verifying the spatial and temporal information of IoT data blocks.
- Cryptographic mechanisms, including asymmetric encryption, hash functions, and digital signatures, enforce IoT data integrity and reliability.
- Smart contracts enable IoT systems to interact autonomously, executing contract clauses automatically when specified conditions are satisfied.
- The survey reviews IoT and blockchain foundations, proposes a BCoT architecture, discusses 5G-beyond networks and applications, and outlines open research issues.
II. INTERNET OF THINGS
IoT connects physical environments with cyberspace through sensing, communication, and industrial applications. Its heterogeneous, decentralized, and resource-constrained nature creates interoperability, privacy, and security challenges.
- IoT connects physical industrial environments to computing cyberspace and supports data-driven smart-industry applications.
- A typical IoT system includes perception, communication, and industrial-application layers.
- The perception layer uses sensors, actuators, controllers, tags, smart meters, and other devices to sense environments and perform actions.
- IoT heterogeneity spans devices, communication protocols, and structured, semi-structured, and nonstructured data, contributing to interoperability, privacy, and security challenges.
- Poor interoperability makes exchanging data and collaborating across decentralized, heterogeneous IoT systems and industrial sectors difficult.
- Resource-constrained IoT devices have limited computing, storage, and battery resources, increasing vulnerability to malicious attacks.
- IoT privacy and security are difficult to preserve because decentralized, heterogeneous, and resource-constrained systems complicate protection and expose data to attacks.
III. BLOCKCHAIN TECHNOLOGIES
Blockchain is a distributed ledger whose consecutively linked blocks are validated across the network and use cryptographic structures to detect tampering.
- A blockchain is a distributed ledger whose blocks reference their immediately preceding blocks through parent-block hash values.The first block is the genesis block and has no parent block.
- New blocks are validated by network nodes and appended to the chain through references to their parent blocks.
- Unauthorized block alterations are detectable because tampering changes hash values and can be identified by other distributed nodes.
- Blockchain integrity relies on ordered hash links between blocks and Merkle tree root hashes covering transactions.
2) Consensus algorithms:
Blockchain consensus algorithms validate newly generated blocks and resolve disagreements among distributed nodes, but their trust assumptions, communication patterns, and resource demands differ.
- Consensus algorithms validate block trustfulness in decentralized environments, with PoW, PoS, and PBFT as typical examples.
- In PoW, miners solve computational puzzles, append validated blocks, and broadcast the results to other nodes.The first node solving the puzzle is called a miner and receives compensation.
- Forks caused by near-simultaneous validation or network latency are typically resolved by retaining the longest chain.Shorter chains are deserted and future validation continues on the longest chain.
- PoW assumes that most computational capability is trustworthy, with 51% generally regarded as the malicious-attack tolerance threshold.
- PoW requires extensive energy-consuming computation, while PoS uses ownership stakes and PBFT uses repeated voting among equal-right nodes.
- Probabilistic algorithms save validated blocks before seeking consensus, whereas deterministic algorithms reach consensus before saving them.Probabilistic approaches can produce bifurcated chains, while deterministic approaches resolve discrepancies through communication rounds.
- Blockchain research increasingly combines or improves consensus algorithms to meet differing application requirements.Examples include Ripple, Algorand, Tendermint, PoA, and PoET.
B. Key Characteristics of Blockchain
Blockchain provides decentralized transaction validation, tamper detection, transparency, traceability, and automated contract execution, while offering pseudonymity rather than full privacy.
- Key Characteristics: Blockchain enables peer-to-peer transaction validation without central-agency intervention, reducing service cost, bottlenecks, and single-point-of-failure risk.
- Key Characteristics: Hash-linked blocks and Merkle trees make falsification detectable because changes invalidate subsequent links or alter the Merkle root.
- Key Characteristics: Cryptographic signatures support non-repudiation because transaction initiators can be verified through corresponding public keys.
- Key Characteristics: Public blockchain transactions are accessible for users to validate, making blockchain data transparent.
- Key Characteristics: Blockchain preserves pseudonymity through anonymous addresses but not full privacy because addresses remain traceable by inference.
- Key Characteristics: Timestamps attached to transactions allow users to verify and trace the origins of historical data items.
- Smart Contracts: Smart contracts automatically enforce embedded contractual clauses when specified conditions are satisfied.
- Smart Contracts: Smart contracts run as executable programs on blockchains, with executions recorded as immutable transactions and access control assigned to functions.
D. Taxonomy of Blockchain Systems
Blockchain systems are classified as public, private, or consortium systems, which trade off decentralization, scalability, flexibility, permission, and consensus arrangements.
- System Types: Public blockchains are accessible to anyone, whereas private systems are controlled by one organization and consortium systems by multiple groups.
- Key Characteristics: Public systems are fully decentralized and difficult to tamper with, while private and consortium systems permit control by dominant organizations or groups.
- Scalability: Public blockchains provide strong decentralization-related properties but have lower validation rates, higher latency, and greater storage consumption.
- Scalability and Flexibility: Private and consortium blockchains offer better scalability and more adjustable configurations than public blockchains.
- Permission: Public blockchains are permissionless, while private and consortium systems can assign different read and transaction permissions.
- Consensus: Public systems commonly use PoW or PoS, private systems use algorithms such as PBFT, PoA, or PoET, and consortium systems combine public and private characteristics.
- Platforms: Examples include Bitcoin and Ethereum for public blockchains, GemOS and MultiChain for private blockchains, and Hyperledger for consortium frameworks.
A. Opportunities of integrating blockchain with IoT
BCoT addresses IoT interoperability, security, traceability, reliability, and autonomous interaction through blockchain mechanisms. Its architecture uses a blockchain-composite layer to abstract heterogeneous IoT layers and provide blockchain-based services.
- Opportunities of integrating blockchain with IoT: BCoT improves IoT interoperability by transforming heterogeneous data and using a P2P overlay network for access across fragmented networks.The blockchain-composite layer provides uniform access across different IoT systems.
- Opportunities of integrating blockchain with IoT: Blockchain transactions improve IoT security through encryption, digital signatures, and automatic firmware updates that remedy vulnerable breaches.The cited design connects blockchain transactions and smart contracts with data protection and firmware maintenance.
- Opportunities of integrating blockchain with IoT: Blockchain provides traceability and reliability by preserving historical transactions and protecting data integrity with cryptographic mechanisms.Historical timestamps support verification, while immutability and cryptography support trustworthy IoT data.
- Opportunities of integrating blockchain with IoT: Smart contracts enable autonomic IoT interactions by executing contract clauses automatically when specified conditions are satisfied.The paper gives automatic payment execution as an example of such interaction.
- Architecture of Blockchain of Things: The blockchain-composite layer mediates between IoT and industrial applications, hiding lower-layer heterogeneity while exposing blockchain-based APIs.This abstraction lowers the difficulty of developing industrial applications.
C. Deployment of BCoT
BCoT deployment assigns blockchain storage across cloud, edge, and IoT devices according to resource constraints, while 5G-beyond integration introduces broader infrastructure challenges and opportunities.
- Deployment of BCoT: IoT device constraints make full blockchain storage difficult, motivating full nodes and partial-storage nodes.Cloud and edge servers may store whole or partial blockchain data, whereas IoT devices may save only partial data.
- Deployment of BCoT: BCoT deployment can support direct interaction between IoT devices and blockchain data held at edge servers near gateways or base stations.The deployment scenario places blockchain storage across cloud and edge infrastructure.
- Deployment of BCoT: Most IoT devices remain lightweight nodes because their storage is limited, despite initiatives for installing blockchain software on embedded devices.Raspberry Pi and ARM-based deployments illustrate attempts to configure blockchain nodes on constrained hardware.
- 5G-beyond networks: Blockchain integration with 5G-beyond networks remains an open research area spanning communications, network management, and computing management.The paper identifies next-generation networks as critical infrastructure for blockchain-enabled IoT.
- 5G-beyond networks: Blockchain can support improved mobile services by integrating fragmented heterogeneous networks and enabling analytics over transaction data.The passage presents these as potential uses in future 5G systems.
B. Blockchain for network management
Blockchain-based network management is discussed as a response to centralization, heterogeneity, and resource-management challenges across SDN, network slicing, cloud, and edge computing.
- Blockchain for network management: Blockchain can address the single-point-of-failure risk of centralized SDN and support security-oriented distributed network management.The paper also notes that incumbent SDN devices may lack capacity for computationally intensive traffic analysis.
- Blockchain for network management: Network slicing can provide separate blockchain services for diverse industrial requirements, but composite environments require joint allocation of network and computing resources.The paper connects network slicing with blockchain services, reliable content sharing, and privacy-preserving data sharing.
- Blockchain for network management: Cloud-only processing of massive IoT data creates traffic bottlenecks, latency, limited context awareness, and privacy exposure, motivating mobile edge computing.Resource-constrained IoT devices commonly upload data to remote cloud servers for processing.
- Blockchain for network management: Blockchain-enabled cloud-edge orchestration must address computational task offloading and incentives for resource sharing across heterogeneous edge servers.Mobile edge servers have weaker and differing computing, memory, storage, and connectivity capabilities than cloud servers.
- Blockchain for network management: Existing offloading studies often assign a task wholly to edge or cloud, leaving dependency-aware partitioning of multiple subtasks as a future research direction.The paper also identifies joint optimization of spectrum, computation, and energy consumption as challenging.
- Applications of Blockchain of Things: BCoT applications span six industrial categories, reflecting a broad application scope for blockchain-enabled IoT.The paper focuses on industrial applications ranging from smart manufacturing to connected vehicles and unmanned aerial vehicles.
A. Smart manufacturing
BCoT is applied to smart manufacturing and supply chains to connect industrial data, improve traceability, and support automated or secure transactions across product life cycles.
- Smart manufacturing: BCoT can interconnect manufacturing IoT systems through P2P networks and enable data sharing across industrial sectors.Different sectors may be served by separate distributed blockchains.
- Smart manufacturing: Blockchain and IoT can associate each product part with a unique identifier and immutable timestamp to help detect forged or low-quality components.The approach targets supply-chain verification across parts supplied by different manufacturers and countries.
- Smart manufacturing: Smart contracts can automate insurance claim settlement in supply chains, improving efficiency and reducing claim-processing time.The cited use case concerns motor insurance after-sale services.
- Food industry: BCoT can improve food-supply-chain visibility by preserving traceability and provenance from raw-material sources through food manufacturing.The paper presents traceability as necessary for food safety and difficult for incumbent IoT to guarantee across the whole chain.
- Food industry: RFID and blockchain proposals demonstrate traceability of food-supply-chain data and support traceable food products for improved food safety.The cited proposals cover a platform from agriculture to food production and related food-safety applications.
- Energy applications: Blockchain-based P2P energy trading is presented as a way to support secure transactions between energy prosumers and consumers without a central broker.Distributed consensus is reported to reduce trading cost in a consortium-blockchain system.
E. Health care
BCoT applications span healthcare, vehicles, and UAVs, where blockchain is presented as supporting privacy, security, traceability, and broader operational trust. The section also frames resource, storage, connectivity, and scalability constraints as open challenges requiring cloud, MEC, or other adaptations.
- Healthcare: Healthcare applications use blockchain to support privacy-preserving and secure management of data generated by medical sensors.Examples include protecting cloud-stored healthcare data and managing private healthcare data.
- Healthcare: Blockchain-enabled tracking of infected or suspected patients can support quarantine measures while protecting patient privacy.
- Internet of vehicles: IoV applications use blockchain to address decentralization, heterogeneity, and non-trustworthiness in message transmission and transaction execution.A cited example develops a blockchain-based trust-management platform for IoV.
- Unmanned aerial vehicles: UAV blockchains can store model, manufacturer, and restricted-region information to help detect and identify UAV misbehavior in time.
- Application-wide benefits: Across applications, BCoT is associated with lower trusted-third-party costs, security assurance, data traceability, authenticity verification, and privacy preservation.
- Open challenges: Resource-constrained IoT devices make energy-intensive consensus and full blockchain storage impractical, motivating cloud or MEC full nodes with lightweight IoT nodes.The passage cites Bitcoin’s blockchain approaching 185 GB by the end of September 2018.
B. Security vulnerability
BCoT inherits security vulnerabilities from both IoT and blockchain systems, while IoT’s wireless, resource-constrained, and distributed setting complicates protection. Proposed responses combine IoT security enhancements with blockchain vulnerability repair, but privacy-preserving mechanisms also remain imperfect.
- IoT security: Wireless IoT networks face eavesdropping, jamming, replay attacks, heavyweight-encryption constraints, and distributed key-management challenges.
- Blockchain security: Blockchain systems add risks including smart-contract defects, BGP message hijacking, and DAO attacks exploiting smart-contract vulnerabilities.The cited DAO example stole $50 million worth of Ethereum.
- Potential solutions: Potential remedies combine IoT security enhancements, such as cooperative jamming and wireless-channel key generation, with repairing blockchain loopholes.
- Privacy leakage: Blockchain anonymity mechanisms based on pseudonyms and one-time accounts do not robustly prevent users or transactions from being inferred.
- Privacy leakage: Mixed-coin schemes can remain vulnerable to realistic attacks that deduce actual transactions, while memory-optimized storage may somewhat reduce privacy leakage.
- Incentives: BCoT incentive mechanisms must accommodate different applications because rewards and processing compensation shape participation in blockchain systems.
E. Difficulty in BDA in BCoT
BCoT analytics is difficult because IoT data is massive and nearly real-time, while devices and blockchain data impose computation, storage, privacy, and throughput constraints. Proposed directions include MEC or cloud support, analytics without decryption, scalable consensus, DAG structures, and private or consortium blockchains.
- Data characteristics: IoT data arrives in massive, heterogeneous, nearly real-time volumes, creating difficulties for conventional big-data analytics in BCoT.The data is also described as having substantial business value for intelligent decision-making.
- Resource and storage constraints: Resource-limited IoT devices cannot directly deploy complicated analytics schemes or store bulky blockchain data, while cloud offloading raises privacy and latency concerns.
- Privacy-preserving analytics: Encrypted or anonymous blockchain data is difficult to analyze because decryption is time-consuming, motivating analytics schemes that avoid decryption.
- Scalability: Blockchain scalability limits large-scale IoT because throughput must handle growing node populations and concurrent workloads.Bitcoin is cited as processing only seven transactions per second.
- Potential solutions: Proposed scalability directions include more scalable consensus, consensus localization, DAG-based structures, and private or consortium blockchains.Private and consortium systems can process transactions faster because participation and control are limited.
- Paper scope: The paper surveys BCoT opportunities, architecture, next-generation-network issues, applications, and open research directions.