42 4 Vol. 42, No. 4 2016 4 ACTA AUTOMATICA SINICA April, 2016 1, 2 1, 3,.,.,,,. DOI,,,,,.., 2016, 42(4): 481 494 10.16383/j.aas.2016.c160158 Blockchain: The State of the Art and Future Trends YUAN Yong 1, 2 WANG Fei-Yue 1, 3 Abstract Blockchain is an emerging decentralized architecture and distributed computing paradigm underlying Bitcoin and other cryptocurrencies, and has recently attracted intensive attention from governments, financial institutions, hightech enterprises, and the capital markets. Blockchain s key advantages include decentralization, time-series data, collective maintenance, programmability and security, and thus is particularly suitable for constructing a programmable monetary system, financial system, and even the macroscopic societal system. In this paper, we proposed a basic model of the blockchain system, discussed the principles, technologies, methods and applications of blockchain and the related Bitcoin systems. We also discussed the smart contract and its applications, and presented the future trends of blockchain-enabled paralleled societies. This paper is aimed at providing helpful guidance and reference for future research efforts. Key words Blockchain, Bitcoin, consensus mechanism, smart contract, paralleled society Citation Yuan Yong, Wang Fei-Yue. Blockchain: the state of the art and future trends. Acta Automatica Sinica, 2016, 42(4): 481 494.,,,. 2016-02-22 2016-03-02 Manuscript received February 22, 2016; accepted March 2, 2016 (71472174, 71102117, 61533019, 71232006, 61233001) Supported by National Natural Science Foundation of China (71472174, 71102117, 61533019, 71232006, 61233001) Recommended by Associate Editor LIN Zong-Li 1. 100190 2. 266109 3. 410073 1. The State Key Laboratory of Management and Control for Complex Systems, Institute of Automation, Chinese Academy of Sciences, Beijing 100190 2. Qingdao Academy of Intelligent Industries, Qingdao 266109 3. Research Center of Military Computational Experiments and Parallel System, National University of Defense Technology, Changsha 410073, / [1].,,.. 2016 1, [2], ;. 2015 12 Linq, ;. 2016, 10
482 42. R3CEV Azure BaaS (Blockchain as a service, ), 40. 2008 (Satoshi nakamoto) : [3],., (Decentralized shared ledger),. ( ).. : ; :, ; : ( ), ; :,., (Ethereum) [4] ; :,.,., 1.0 2.0 3.0 [1]., 2.0, P2P.,, 1.0.,,. 2016 2, Web of Science EI Village, /blockchain 2 [5 6] 9 [6 14].. : 1 ; 2 ; 3 4 ; 5 ; 6 ; 7. 1. Blockchain.info, 7 500 120 000, 40 [15]. coinmarketcap.com, 2016 2, 675, 67, 86 %, [16]. ( ) 1 500, 389.50 59, 2015 GDP 144 ( ).,,. 2027, 10 % GDP [17]. ( ) 2009 1 4,., 10, ; 2010 5, 1 25.,, 2013 11 1 242, 1 241.98. CoinDesk, 6,
4 : 483 [18].,, (Proof of work, PoW). PoW (, ),,.,.., ( ).,. [19].,., ( ), ; ( ).,., [20].. ( ),., ( 1 ),. ; ( ) PoW ( ).., ( ) ;...,,. 1 Fig. 1 The Bitcoin ecosystem
484 42.,. 2,,.. 2.,., ; ; ;, ; ;.,. 2.1 Fig. 2 2 A basic framework of blockchain. Merkle,,,. Merkle. : 3, (Header) (Body). (Version) (Prev-block) (Bits) PoW (Nonce) Merkle (Merkle-root) (Timestamp) [21]. PoW, Nonce.. Merkle Merkle. Fig. 3 3 The structure of blocks :,.,,,.,,
4 : 485.,,,, [19]. :.,.,. (Proof of existence),,.,,. :,,. ( ),., ( ), ( ) ( ), ( ). SHA256, SHA256 256 (32 )., SHA256 (2 256 ) ( ),. Merkle : Merkle,. 3, Merkle ( ), ( Merkle ). Merkle, Merkle, Merkle. Merkle Merkle, [22], Merkle patricia tree [4]. Merkle :, ; Merkle,, ( ) [3]., 3 6, 6 Merkle ( 6, 5, 56, 78, 5 678, 1 234)., N log 2 N.. :, RSA Elgamal Rabin D-H ECC ( ).,., ( ), ;. ( A) ( B) B, B. ; A B, B A A ;,., 4 : 256. 2 256,., 256 SHA256 Base58, 50 ; Secp256k1 65. SHA256 RIPEMD160 20 ( hash160 ), SHA256 Base58 33 [19].,.
486 42 Fig. 4 4 The asymmetric cryptography of the Bitcoin system,... 2.2.,,. : (Peer-to-peer network, P2P ). P2P,.,.., ;, 2016 2, 60 GB.,, 2.1. :,. [4]. [3] : 1) ; 2) ; 3) ; 4), ; 5), ; 6),.,,.,,,. [19]. : P2P.., ;,., P2P,, ;,
4 : 487, ;,,.,.,,.,, ;,. 2.3., ;.. (Proof of work, PoW). (Proof of stake, PoS) [23] (Delegated proof of stake, DPOS) [24].. PoW : PoW,., ( ) SHA256 ( ),. :, (Nonce) 3 SHA256. 10., PoW ( 3 ) [19] : 1., Coinbase, ; 2. Merkle,, Nonce ; 3. Nonce 1; SHA256,, ; 3 ; 4., Merkle.,,,. Blockchain.info, 2016 2, 17, 398 346 0000000000000000077f754f22f21629a7975cf., 16 17 16 17., PoW, SHA256,., 2016 1, 800 000 000 Gh/s, 8 10 18, Top500. PoW, ; PoW, ( ), 10. PoS : PoS PoW., PoS PoW. PoS PoW. (Coin days).
488 42., 10 10, 100 ; 5, 50., PoS, PoS., PoW, PoS. PoW., PoS, PoW, PoS. DPoS : DPoS, 101, ( ).,. 100.,,., 99 % [24]., PoW PoS, DPoS,,., PoW+PoS (Proof of activity)., PoW,, PoS DPoS. 2.4,.,.,,.., PoW, PoW.,. PoW,. :. 50, 4 (21 ),, 2 100 [19].,. ( Coinbase ). ( 1 ),.,,. :,,. Bitcoinmining.com, 13 [25]. PPLNS (Pay per last N shares) PPS (Pay per share) PROP (PROPortionately). (Share), PPLNS, N ; PPS,
4 : 489 ; PROP.,. 2.5.,,. ;,., ; 5..,,.,, ;,.,, P2PKH (Pay to public key hash) [19].., ( ), ; ; ; N M, M N, N M..,.,.., [4]. 3,.. : ( )., Merkle. 5 3., ( ), ( ) [7]. :.,,. ; Factom
490 42 [26]. :.,,, ;, P2P ;,,, ; SWIFT ; R3CEV. :,., ;,,,.,, Airbnb ;,. :. ;,., [27] ;,.,, (Public blockchain) (Consortium blockchain) (Private blockchain).,, PoW PoS.. ( ),, 10 5 ;,,., 2,. 4,.. 4.1., PoW 51 %, 51 %. 60 %, 51 %, [1]. 51 %, 51 %. PoS 51 %, N@S (Nothing at stake). PoW 51 % [4],..,, SHA256 2 48,.. ( ).,,
4 : 491. 4.2. :., 60 GB, [28]. : 7, ( VISA 10 000 ) [1] ; : 10, 10,. 4.3 PoW, SHA256,,,.,.,., Primecoin ( ) ( ) SHA256 [29].. 4.4,,.,., (Block withholding attacks),.,., [30].,.,,,. 5 1994 Nick Szabo,,,... ( ),,,..,.,.,,... 5 :, ( ), P2P. ( )..
492 42 Fig. 5 5 The rationale of smart contracts., P2P. P2P,.,..,, ( ).. ; ;, [1]..,,, 2.0 3.0 ;,,, (Decentralized application, Dapp) (Decentralized autonomous organization, DAO) (Decentralized autonomous corporation, DAC) (Decentralized autonomous society, DAS).,. IF-THEN,. WHAT-IF [31 32]. 6, + 4.0. + CPS (Cyber-physical systems, CPS), + +, (Cyber-physical-social systems, CPSS)., CPSS, [33]. CPSS,., :,.,,,.,,.,,, ;, [34]. ACP ( Artificial societies
4 : 493 Computational experiments Parallel execution) [35]. ACP., P2P (Agent). Dapp, DAC DAO, DAS, ACP [36]., WHAT-IF.,,.,,. 7,..,.,. References 1 Swan M. Blockchain: Blueprint for a New Economy. USA: O Reilly Media Inc., 2015. 2 Technical report by the UK government chief scientific adviser [Online], available: https://www.gov.uk/government/ uploads/system/uploads/attachment data/file/492972/gs- 16-1-distributed-ledger-technology.pdf, February 21, 2016 3 Nakamoto S. Bitcoin: a peer-to-peer electronic cash system [Online], available: https://bitcoin.org/bitcoin.pdf, 2009 4 Ethereum White Paper. A next-generation smart contract and decentralized application platform [Online], available: https://github.com/ethereum/wiki/wiki/white- Paper, November 12, 2015 5 Ding Wei. Block chain based instrument data management system. China Instrumentation, 2015, (10): 15 17 (.., 2015, (10): 15 17) 6 Zhao He, Li Xiao-Feng, Zhan Li-Kui, Wu Zhong-Cheng. Data integrity protection method for microorganism sampling robots based on blockchain technology. Journal of Huazhong University of Science and Technology (Natural Science Edition), 2015, 43(Z1): 216 219 (,,,.. ( ), 2015, 43( ): 216 219) 7 Swan M. Blockchain thinking: the brain as a decentralized autonomous corporation. IEEE Technology and Society Magazine, 2015, 34(4): 41 52 8 Davidson Eric. Letter. New Scientist, 2015, 228(3043): 52 52 9 Anonymous. New kid on the blockchain. New Scientist, 2015, 225(3009): 7 10 Godsiff P. Bitcoin: bubble or blockchain. In: Proceedings of the 9th KES International Conference on Agent and Multi-Agent Systems: Technologies and Applications (KES- AMSTA). Sorrento, Italy: Springer, 2015, 38: 191 203 11 Kraft D. Difficulty control for blockchain-based consensus systems. Peer-to-Peer Networking and Applications, 2016, 9(2): 397 413 12 Wilson D, Ateniese G. From pretty good to great: enhancing PGP using Bitcoin and the blockchain. In: Proceedings of the 9th International Conference on Network and System Security. New York: Springer International Publishing, 2015, 9408: 368 375 13 Zyskind G, Nathan O, Pentland A S. Decentralizing privacy: using blockchain to protect personal data. In: Proceedings of the 2015 IEEE Security and Privacy Workshops (SPW 2015). San Jose, CA: IEEE, 2015. 180 184 14 Kypriotaki K N, Zamani E D, Giaglis G M. From Bitcoin to decentralized autonomous corporations: extending the application scope of decentralized peer-to-peer networks and blockchains. In: Proceedings of the 17th International Conference on Enterprise Information Systems(ICEIS2015). 2015, 3: 284 290 15 Blockchain Monitoring Website [Online], available: https://blockchain.info/, January 8, 2016 16 Cryptocurrency Monitoring Website [Online], available: http://coinmarketcap.com/, November 24, 2015 17 World Economic Forum Survey [Online], available: http:// www.coinfox.info/news/3184-world-economic-forum-survey -10-of-global-gdp-may-be-stored-with-blockchain-technolog y-by-2027, February 21, 2016 18 CoinDesk Report [Online], available: http://www. bitcoin86.com/news/3527.html, February 21, 2016 19 Antonopoulos A M. Mastering Bitcoin: Unlocking Digital Cryptocurrencies. USA: O Reilly Media Inc., 2014. 20 Fan Jie, Yi Le-Tian, Shu Ji-Wu. Research on the technologies of Byzantine system. Journal of Software, 2013, 24(6): 1346 1360 (,,.., 2013, 24(6): 1346 1360) 21 Bitcoin Sourcecode [Online], available: https://github.com/ bitcoin/bitcoin/, January 18, 2016 22 Merkle R C. Protocols for public key cryptosystems. In: Proceedings of the 1980 IEEE Symposium on Security and Privacy. Oakland, CA, USA: IEEE, 1980. 122
494 42 23 Larimer D. Transactions as proof-of-stake [Online], available: http://7fvhfe.com1.z0.glb.clouddn.com/@/wpcontent/uploads/2014/01/transactionsasproofofstake10. pdf, 2013 24 Larimer D. Delegated proof-of-stake white paper [Online], available: http://www.bts.hk/dpos-baipishu.html, 2014 25 Bitcoinmining Article [Online], available: https://www. bitcoinmining.com/bitcoin-mining-pools, December 8, 2015 26 Factom White Paper [Online], available: http://bite01. com/bit/1421, December 29, 2015 27 Brito J, Shadab H, Castillo A. Bitcoin financial regulation: securities, derivatives, prediction markets, and gambling. The Columbia Science & Technology Law Review, 2014, 16: 144 221 28 Eyal I, Efe Gencer A, Sirer E G, van Renesse R. Bitcoin-NG: a scalable blockchain protocol. Cryptography and Security, arxiv: 1510.02037 29 Primecoin Website [Online], available: http:// primecoin.io/, February 9, 2016 30 Courtois N T, Bahack L. On subversive miner strategies and block withholding attack in Bitcoin digital currency. Cryptography and Security, arxiv: 1402.1718 31 Wang Fei-Yue. Computational experiments for behavior analysis and decision evaluation of complex systems. Journal of System Simulation, 2004, 16(5): 893 897 (.., 2004, 16(5): 893 897) 32 Wang Fei-Yue, Qiu Xiao-Gang, Zeng Da-Jun, Cao Zhi- Dong, Fan Zong-Chen. A computational experimental platform for emergency response based on parallel systems. Complex Systems and Complexity Science, 2010, 7(4): 1 10 (,,,,.., 2010, 7(4): 1 10) 33 Wang Fei-Yue, Wang Xiao, Yuan Yong, Wang Tao, Lin Yi-Lun. Social computing and computational societies: the foundation and consequence of smart societies. Chinese Science Bulletin, 2015, 60(5 6): 460 469 (,,,,. :., 2015, 60(5 6): 460 469) 34 Wang Fei-Yue. Software-defined systems and knowledge automation: a parallel paradigm shift from Newton to Merton. Acta Automatica Sinica, 2015, 41(1): 1 8 (. :., 2015, 41(1): 1 8) 35 Wang Fei-Yue. Artificial societies, computational experiments, and parallel systems: a discussion on computational theory of complex social-economic systems. Complex Systems and Complexity Science, 2004, 1(4): 25 35 (. :., 2004, 1(4): 25 35) 36 Wang Fei-Yue, Jiang Zheng-Hua, Dai Ru-Wei. Population studies and artificial societies: a discussion of artificial population systems and their applications. Complex Systems and Complexity Science, 2005, 2(1): 1 9 (,,. :., 2005, 2(1): 1 9). 2008... E-mail: yong.yuan@ia.ac.cn (YUAN Yong Associate professor at the State Key Laboratory of Management and Control for Complex Systems, Institute of Automation, Chinese Academy of Sciences. He received his Ph. D. degree in computer software and theory from Shandong University of Science and Technology in 2008. His research interest covers business intelligence and computational advertising. Corresponding author of this paper.),.,. E-mail: feiyue.wang@ia.ac.cn (WANG Fei-Yue Professor at the State Key Laboratory of Management and Control for Complex Systems, Institute of Automation, Chinese Academy of Sciences. He is also a professor at the Research Center of Military Computational Experiments and Parallel System, National University of Defense Technology. His research interest covers modeling, analysis, and control of intelligent systems and complex systems.)