{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,9]],"date-time":"2026-02-09T23:12:13Z","timestamp":1770678733421,"version":"3.49.0"},"reference-count":88,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2019,10,11]],"date-time":"2019-10-11T00:00:00Z","timestamp":1570752000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Future Internet"],"abstract":"<jats:p>In the last few years, we have been witnessing the convergence of the physical with the digital world. The Internet of Things (IoT) is progressing at a fast pace, and IoT devices are becoming pervasive in our physical environments, bringing the vision of Intelligent Environments closer to reality. At the same time, the newly-introduced blockchain technology is offering for the first time ever cryptographically proven trust based on a set of mutually untrusted nodes. Blockchain technology thus has the potential to become a key component of many IoT systems, offering them an unprecedented level of accountability, transparency, and reliability. This paper first lays out the principles on which blockchain systems are operating, along with descriptions of the most noteworthy blockchain implementations. It then presents a number of systems through which blockchains may interact with external systems and third-party data sources. Finally, it provides a survey of the state-of-the-art blockchain-based systems targeting IoT applications.<\/jats:p>","DOI":"10.3390\/fi11100213","type":"journal-article","created":{"date-parts":[[2019,10,14]],"date-time":"2019-10-14T03:54:13Z","timestamp":1571025253000},"page":"213","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":26,"title":["Blockchain Technology for Intelligent Environments"],"prefix":"10.3390","volume":"11","author":[{"given":"Spyros","family":"Voulgaris","sequence":"first","affiliation":[{"name":"Department of Informatics, Athens University of Economics and Business, 10434 Athens, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9100-1081","authenticated-orcid":false,"given":"Nikos","family":"Fotiou","sequence":"additional","affiliation":[{"name":"Department of Informatics, Athens University of Economics and Business, 10434 Athens, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vasilios A.","family":"Siris","sequence":"additional","affiliation":[{"name":"Department of Informatics, Athens University of Economics and Business, 10434 Athens, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0030-4808","authenticated-orcid":false,"given":"George C.","family":"Polyzos","sequence":"additional","affiliation":[{"name":"Department of Informatics, Athens University of Economics and Business, 10434 Athens, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mikael","family":"Jaatinen","sequence":"additional","affiliation":[{"name":"Ericsson, 00240 Helsinki, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yannis","family":"Oikonomidis","sequence":"additional","affiliation":[{"name":"Synelixis Solutions SA, 14343 Athens, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,10,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1186\/2192-1962-3-12","article-title":"Intelligent Environments: A manifesto","volume":"3","author":"Augusto","year":"2013","journal-title":"Human-Centric Comput. Inf. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Yu, Z., Liscano, R., Chen, G., Zhang, D., and Zhou, X. (2010). A Middleware for Intelligent Environments and the Internet of Things. Ubiquitous Intelligence and Computing, Springer.","DOI":"10.1007\/978-3-642-16355-5"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2137","DOI":"10.3390\/s150102137","article-title":"Integrated semantics service platform for the Internet of Things: A case study of a Smart Office","volume":"15","author":"Ryu","year":"2015","journal-title":"Sensors"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1002\/isaf.1424","article-title":"Toward an ontology-driven blockchain design for supply-chain provenance","volume":"25","author":"Kim","year":"2018","journal-title":"Intell. Syst. Account. Finance Manag."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1109\/MIE.2017.2649104","article-title":"The future of industrial communication: Automation networks in the era of the Internet of Things and Industry 4.0","volume":"11","author":"Wollschlaeger","year":"2017","journal-title":"IEEE Ind. Electron. Mag."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1454","DOI":"10.1016\/j.jclepro.2016.10.006","article-title":"A review of Internet of Things for smart home: Challenges and solutions","volume":"140","author":"Stojkoska","year":"2017","journal-title":"J. Clean. Prod."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Dorri, A., Kanhere, S.S., Jurdak, R., and Gauravaram, P. (2017, January 13\u201317). Blockchain for IoT security and privacy: The case study of a smart home. Proceedings of the 2017 IEEE International Conference on Pervasive Computing and Communications Workshops (PerCom Workshops), Kona, HI, USA.","DOI":"10.1109\/PERCOMW.2017.7917634"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"551","DOI":"10.1007\/s00779-015-0844-1","article-title":"Touch-less Interactive Augmented Reality Game on Vvision-based Wearable Device","volume":"19","author":"Lv","year":"2015","journal-title":"Personal Ubiquitous Comput."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1109\/JIOT.2015.2417684","article-title":"An IoT-aware architecture for smart healthcare systems","volume":"2","author":"Catarinucci","year":"2015","journal-title":"IEEE Internet   Things J."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1109\/MCE.2016.2556879","article-title":"Everything you wanted to know about Smart Cities: The Internet of Things is the Backbone","volume":"5","author":"Mohanty","year":"2016","journal-title":"IEEE Consum. Electron. Mag."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1007\/s10796-014-9492-7","article-title":"The Internet of Things: A Survey","volume":"17","author":"Li","year":"2015","journal-title":"Inf. Syst. Front."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1007\/s10796-014-9489-2","article-title":"The Internet of Things\u2014A survey of topics and trends","volume":"17","author":"Whitmore","year":"2015","journal-title":"Inf. Syst. Front."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2347","DOI":"10.1109\/COMST.2015.2444095","article-title":"Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications","volume":"17","author":"Guizani","year":"2015","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2292","DOI":"10.1109\/ACCESS.2016.2566339","article-title":"Blockchains and Smart Contracts for the Internet of Things","volume":"4","author":"Christidis","year":"2016","journal-title":"IEEE Access"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Zheng, Z., Xie, S., Dai, H., Chen, X., and Wang, H. (2017, January 25\u201330). An overview of blockchain technology: Architecture, consensus, and future trends. Proceedings of the 2017 IEEE International Congress on Big Data (BigData Congress), Honolulu, HI, USA.","DOI":"10.1109\/BigDataCongress.2017.85"},{"key":"ref_16","unstructured":"Nakamoto, S. (2019, September 20). Bitcoin: A Peer-to-Peer Electronic Cash System. Available online: http:\/\/bitcoin.org\/bitcoin.pdf."},{"key":"ref_17","unstructured":"(2019, September 20). Ethereum. Available online: https:\/\/ethereum.org."},{"key":"ref_18","unstructured":"(2019, September 20). Litecoin. Available online: https:\/\/litecoin.org\/."},{"key":"ref_19","unstructured":"Reed, J. (2017). Litecoin: An Introduction to Litecoin Cryptocurrency and Litecoin Mining, CreateSpace Independent Publishing Platform."},{"key":"ref_20","unstructured":"(2019, September 20). Monero. Available online: https:\/\/www.getmonero.org\/."},{"key":"ref_21","unstructured":"(2019, September 20). Dash. Available online: https:\/\/www.dash.org\/."},{"key":"ref_22","unstructured":"(2019, September 20). Dogecoin. Available online: https:\/\/www.dogecoin.com\/."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Androulaki, E., Barger, A., Bortnikov, V., Cachin, C., Christidis, K., De Caro, A., Enyeart, D., Ferris, C., Laventman, G., and Manevich, Y. (2018, January 23\u201326). Hyperledger Fabric: A Distributed Operating System for Permissioned Blockchains. Proceedings of the Thirteenth EuroSys Conference, Porto, Portugal.","DOI":"10.1145\/3190508.3190538"},{"key":"ref_24","unstructured":"Deetman, S. (2019, September 20). Bitcoin Could Consume as Much Electricity as Denmark by 2020. Available online: https:\/\/motherboard.vice.com\/en_us\/article\/aek3za\/bitcoin-could-consume-as-much-electricity-as-denmark-by-2020."},{"key":"ref_25","unstructured":"QuantumMechanic (2019, September 20). Proof of Stake. Available online: https:\/\/bitcointalk.org\/index.php?topic=27787.0."},{"key":"ref_26","unstructured":"(2019, September 20). Cardano. Available online: https:\/\/whycardano.com."},{"key":"ref_27","unstructured":"(2019, September 20). The Lisk Protocol. Available online: https:\/\/lisk.io\/documentation\/lisk-protocol."},{"key":"ref_28","unstructured":"(2019, September 20). Blackcoin. Available online: https:\/\/blackcoin.org\/blackcoin-pos-protocol-v2-whitepaper.pdf."},{"key":"ref_29","unstructured":"King, S., and Nadal, S. (2019, September 20). Peercoin \u2013 Secure & Sustainable Cryptocoin. Available online: https:\/\/peercoin.net\/whitepaper."},{"key":"ref_30","unstructured":"(2019, September 20). Nxt White Paper. Available online: https:\/\/bravenewcoin.com\/assets\/Whitepapers\/NxtWhitepaper-v122-rev4.pdf."},{"key":"ref_31","unstructured":"(2019, September 20). Proof of Authority. Available online: https:\/\/github.com\/paritytech\/parity\/wiki\/Proof-of-Authority-Chains."},{"key":"ref_32","unstructured":"Angelis, S.D., Aniello, L., Baldoni, R., Lombardi, F., Margheri, A., and Sassone, V. (2018, January 6\u20139). PBFT vs proof-of-authority: Applying the CAP theorem to permissioned blockchain. Proceedings of the Italian Conference on Cyber Security, Milan, Italy."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1145\/322186.322188","article-title":"Reaching Agreement in the Presence of Faults","volume":"27","author":"Pease","year":"1980","journal-title":"J. ACM"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"382","DOI":"10.1145\/357172.357176","article-title":"The Byzantine Generals Problem","volume":"4","author":"Lamport","year":"1982","journal-title":"ACM Trans. Program. Lang. Syst."},{"key":"ref_35","first-page":"173","article-title":"Practical Byzantine fault tolerance","volume":"99","author":"Castro","year":"1999","journal-title":"OSDI"},{"key":"ref_36","unstructured":"(2019, September 20). Intel: Sawtooth Lake. Available online: https:\/\/intelledger.github.io\/."},{"key":"ref_37","unstructured":"(2019, September 20). Hyperledger Sawtooth. Available online: https:\/\/www.hyperledger.org\/projects\/sawtooth."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Siris, V.A., Dimopoulos, D., Voulgaris, S., Fotiou, N., and Polyzos, G.C. (2019, January 15\u201318). OAuth 2.0 Meets Blockchain for Authorization in Constrained IoT Environments. Proceedings of the 2019 IEEE 5th World Forum on Internet of Things (WF-IoT), Limerick, Ireland.","DOI":"10.1109\/WF-IoT.2019.8767223"},{"key":"ref_39","unstructured":"Buterin, V. (2019, September 20). A Next-Generation Smart Contract and Decentralized Application Platform. Available online: https:\/\/github.com\/ethereum\/wiki\/wiki\/White-Paper."},{"key":"ref_40","unstructured":"Wood, G. (2019, September 20). Ethereum: A Secure Decentralised Generalised Transaction Ledger. Available online: https:\/\/github.com\/ethereum\/yellowpaper."},{"key":"ref_41","unstructured":"Kiayias, A., Miller, A., and Zindros, D. (2019, September 20). Non-Interactive Proofs of Proof-of-Work. Available online: https:\/\/eprint.iacr.org\/2017\/963."},{"key":"ref_42","unstructured":"(2019, September 20). Low-Level Virtual Machine (LLVM): A Compiler Technologies Umbrella Project. Available online: https:\/\/llvm.org."},{"key":"ref_43","unstructured":"IOTA (2019, September 20). Cryptographic Vulnerabilities in IOTA. Available online: https:\/\/medium.com\/@neha\/cryptographic-vulnerabilities-in-iota-9a6a9ddc4367."},{"key":"ref_44","unstructured":"Heilman, E., Narula, N., Dryja, T., and Virza, M. (2019, September 20). IOTA Vulnerability Report: Cryptanalysis of the Curl Hash Function Enabling Practical Signature Forgery Attacks on the IOTA Cryptocurrency. Available online: https:\/\/github.com\/mit-dci\/tangled-curl\/blob\/master\/vuln-iota.md."},{"key":"ref_45","unstructured":"(2019, September 20). Hyperledger Indy. Available online: https:\/\/www.hyperledger.org\/projects\/hyperledger-indy."},{"key":"ref_46","unstructured":"(2019, September 20). Decentralized Identifiers (DIDs) v0.12 Data Model and Syntaxes for Decentralized Identifiers (DIDs). Available online: https:\/\/w3c-ccg.github.io\/did-spec\/."},{"key":"ref_47","unstructured":"(2019, September 20). Sovrin. Available online: https:\/\/sovrin.org\/."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Aublin, P., Mokhtar, S.B., and Qu\u00e9ma, V. (2013, January 8\u201311). RBFT: Redundant Byzantine Fault Tolerance. Proceedings of the 2013 IEEE 33rd International Conference on Distributed Computing Systems, Philadelphia, PA, USA.","DOI":"10.1109\/ICDCS.2013.53"},{"key":"ref_49","unstructured":"(2019, September 20). MultiChain. Available online: https:\/\/www.multichain.com\/."},{"key":"ref_50","unstructured":"(2019, September 20). CoinSpark. Available online: http:\/\/coinspark.org."},{"key":"ref_51","unstructured":"Ali, M., Nelson, J.C., Shea, R., and Freedman, M.J. (2016, January 22\u201324). Blockstack: A Global Naming and Storage System Secured by Blockchains. Proceedings of the USENIX Annual Technical Conference, Denver, CO, USA."},{"key":"ref_52","unstructured":"(2019, September 20). Corda. Available online: https:\/\/www.corda.net\/."},{"key":"ref_53","unstructured":"Hearn, M. (2019, September 20). Corda: A distributed ledger. Available online: https:\/\/www.corda.net\/content\/corda-technical-whitepaper.pdf."},{"key":"ref_54","unstructured":"(2019, September 20). Blockchain Oracles Will Make Smart Contracts Fly. Available online: https:\/\/hackernoon.com\/oracles-help-smart-contracts-resolve-subjective-events-d81639d8291c."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Zhang, F., Cecchetti, E., Croman, K., Juels, A., and Shi, E. (2016, January 24\u201328). Town Crier: An Authenticated Data Feed for Smart Contracts. Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security, Vienna, Austria.","DOI":"10.1145\/2976749.2978326"},{"key":"ref_56","unstructured":"(2019, September 20). Oraclize. Available online: https:\/\/oraclize.it."},{"key":"ref_57","unstructured":"Benet, J. (2014). IPFS\u2014Content Addressed, Versioned, P2P File System. arXiv."},{"key":"ref_58","unstructured":"(2019, September 20). TLSNotary\u2014A Mechanism for Independently Audited HTTPS Sessions. Available online: https:\/\/tlsnotary.org\/TLSNotary.pdf."},{"key":"ref_59","unstructured":"(2019, September 20). ChainLink. Available online: https:\/\/www.smartcontract.com\/link."},{"key":"ref_60","unstructured":"(2019, September 20). Hivemind. Available online: http:\/\/bitcoinhivemind.com."},{"key":"ref_61","unstructured":"(2019, September 20). Off-Chain Computation Solutions for Ethereum Developers. Available online: https:\/\/medium.com\/@YondonFu\/off-chain-computation-solutions-for-ethereum-developers-507b23355b17."},{"key":"ref_62","unstructured":"(2019, September 20). TrueBit. Available online: https:\/\/truebit.io."},{"key":"ref_63","unstructured":"Corporation, M. (2019, September 20). The Coco Framework Technical Overview. Available online: https:\/\/github.com\/Azure\/coco-framework\/blob\/master\/docs\/Coco%20Framework%20whitepaper.pdf."},{"key":"ref_64","unstructured":"Corporation, H. (2019, September 20). Hdac: Transaction Innovation\u2014IoT Contract & M2M Transaction Platform Based on Blockchain, Whitepaper. Available online: https:\/\/github.com\/Hdactech\/doc\/wiki\/Whitepaper."},{"key":"ref_65","unstructured":"(2019, September 20). Kaleido. Available online: https:\/\/kaleido.io\/."},{"key":"ref_66","unstructured":"(2019, September 20). PokitDok. Available online: https:\/\/pokitdok.com\/."},{"key":"ref_67","unstructured":"(2019, September 20). Azure Eventhub. Available online: https:\/\/docs.microsoft.com\/en-us\/azure\/event-hubs\/."},{"key":"ref_68","unstructured":"(2019, September 20). Azure StreamAnalytics. Available online: https:\/\/azure.microsoft.com\/en-us\/services\/stream-analytics\/."},{"key":"ref_69","unstructured":"Kreps, J., Corp, L., Narkhede, N., Rao, J., and Corp, L. (2011, January 12\u201316). Kafka: A Distributed Messaging System for Log Processing. Proceedings of the 6th International Workshop on Networking Meets Databases (NetDB), Athens, Greece."},{"key":"ref_70","unstructured":"Hintjens, P. (2019, September 20). ZeroMQ: An Open-Source Universal Messaging Library. Available online: http:\/\/zguide.zeromq.org\/page:all."},{"key":"ref_71","unstructured":"Chen, J. (2019, September 20). Flowchain: A Distributed Ledger Designed for Peer-to-Peer IoT Networks and Real-Time Data Transactions. Available online: https:\/\/www.flowchain.co\/Flowchain-WhitePaper.pdf."},{"key":"ref_72","doi-asserted-by":"crossref","unstructured":"Stoica, I., Morris, R., Karger, D., Kaashoek, M.F., and Balakrishnan, H. (2001, January 27\u201331). Chord: A Scalable Peer-to-peer Lookup Service for Internet Applications. Proceedings of the 2001 Conference on Applications, Technologies, Architectures, and Protocols for Computer Communications, San Diego, CA, USA.","DOI":"10.1145\/383059.383071"},{"key":"ref_73","unstructured":"Long, C., Zhao, B., and Shi, Q. (2019, September 20). Decentralized Infrastructure for Next Generation Internet of Things. Available online: https:\/\/www.cpchain.io\/CPChain_Whitepaper_English.pdf."},{"key":"ref_74","unstructured":"(2019, September 20). IOTA Marketplace. Available online: https:\/\/data.iota.org\/."},{"key":"ref_75","unstructured":"Popov, S. (2019, September 20). The Tangle, White Paper. Available online: https:\/\/iotatoken.com\/IOTA_Whitepaper.pdf."},{"key":"ref_76","unstructured":"(2019, September 20). Masked Authenticated Messaging. Available online: https:\/\/blog.iota.org\/introducing-masked-authenticated-messaging-e55c1822d50e."},{"key":"ref_77","unstructured":"Haenni, R. (2019, September 20). Datum Network: The Decentralized Data Marketplace. Available online: https:\/\/blockstack.org\/whitepaper.pdf."},{"key":"ref_78","doi-asserted-by":"crossref","unstructured":"Buldas, A., Truu, A., Laanoja, R., and Gerhards, R. (2014). Efficient Record-Level Keyless Signatures for Audit Logs. Nordic Conference on Secure IT Systems, Springer.","DOI":"10.1007\/978-3-319-11599-3_9"},{"key":"ref_79","unstructured":"(2019, September 20). Tilepay. Available online: http:\/\/www.tilepay.org."},{"key":"ref_80","unstructured":"(2019, September 20). Catenis. Available online: http:\/\/blockchainofthings.com."},{"key":"ref_81","unstructured":"(2019, September 20). The Blockchain Interface Company. Available online: https:\/\/www.riddleandcode.com\/."},{"key":"ref_82","unstructured":"(2019, September 20). Chronicled. Available online: http:\/\/www.chronicled.com\/."},{"key":"ref_83","unstructured":"(2019, September 20). Slock.it. Available online: https:\/\/slock.it."},{"key":"ref_84","unstructured":"(2019, September 20). LO3 Energy. Available online: https:\/\/lo3energy.com\/."},{"key":"ref_85","unstructured":"(2019, September 20). Gridgularity. Available online: http:\/\/gridsingularity.com."},{"key":"ref_86","unstructured":"(2019, September 20). SolarCoin. Available online: https:\/\/solarcoin.org."},{"key":"ref_87","unstructured":"(2019, September 20). Farmshare. Available online: http:\/\/farmshare.org."},{"key":"ref_88","unstructured":"(2019, September 20). Provenance. Available online: https:\/\/www.provenance.org\/."}],"container-title":["Future Internet"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-5903\/11\/10\/213\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:25:29Z","timestamp":1760189129000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-5903\/11\/10\/213"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,10,11]]},"references-count":88,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2019,10]]}},"alternative-id":["fi11100213"],"URL":"https:\/\/doi.org\/10.3390\/fi11100213","relation":{},"ISSN":["1999-5903"],"issn-type":[{"value":"1999-5903","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,10,11]]}}}