Homeland Security Bill is Overkill, Bitcoin Isn't Good For

Agreement with Satoshi – On the Formalization of Nakamoto Consensus

Cryptology ePrint Archive: Report 2018/400
Date: 2018-05-01
Author(s): Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Alexei Zamyatin, Edgar Weippl

Link to Paper


Abstract
The term Nakamoto consensus is generally used to refer to Bitcoin's novel consensus mechanism, by which agreement on its underlying transaction ledger is reached. It is argued that this agreement protocol represents the core innovation behind Bitcoin, because it promises to facilitate the decentralization of trusted third parties. Specifically, Nakamoto consensus seeks to enable mutually distrusting entities with weak pseudonymous identities to reach eventual agreement while the set of participants may change over time. When the Bitcoin white paper was published in late 2008, it lacked a formal analysis of the protocol and the guarantees it claimed to provide. It would take the scientific community several years before first steps towards such a formalization of the Bitcoin protocol and Nakamoto consensus were presented. However, since then the number of works addressing this topic has grown substantially, providing many new and valuable insights. Herein, we present a coherent picture of advancements towards the formalization of Nakamoto consensus, as well as a contextualization in respect to previous research on the agreement problem and fault tolerant distributed computing. Thereby, we outline how Bitcoin's consensus mechanism sets itself apart from previous approaches and where it can provide new impulses and directions to the scientific community. Understanding the core properties and characteristics of Nakamoto consensus is of key importance, not only for assessing the security and reliability of various blockchain systems that are based on the fundamentals of this scheme, but also for designing future systems that aim to fulfill comparable goals.

References
[AAC+05] Amitanand S Aiyer, Lorenzo Alvisi, Allen Clement, Mike Dahlin, Jean-Philippe Martin, and Carl Porth. Bar fault tolerance for cooperative services. In ACM SIGOPS operating systems review, volume 39, pages 45–58. ACM, 2005.
[ABSFG08] Eduardo A Alchieri, Alysson Neves Bessani, Joni Silva Fraga, and Fab´ıola Greve. Byzantine consensus with unknown participants. In Proceedings of the 12th International Conference on Principles of Distributed Systems, pages 22–40. SpringerVerlag, 2008.
[AFJ06] Dana Angluin, Michael J Fischer, and Hong Jiang. Stabilizing consensus in mobile networks. In Distributed Computing in Sensor Systems, pages 37–50. Springer, 2006.
[AJK05] James Aspnes, Collin Jackson, and Arvind Krishnamurthy. Exposing computationally-challenged byzantine impostors. Department of Computer Science, Yale University, New Haven, CT, Tech. Rep, 2005.
[AMN+16] Ittai Abraham, Dahlia Malkhi, Kartik Nayak, Ling Ren, and Alexander Spiegelman. Solidus: An incentive-compatible cryptocurrency based on permissionless byzantine consensus. https://arxiv.org/abs/1612.02916, Dec 2016. Accessed: 2017-02-06.
[AS98] Yair Amir and Jonathan Stanton. The spread wide area group communication system. Technical report, TR CNDS-98-4, The Center for Networking and Distributed Systems, The Johns Hopkins University, 1998.
[Bag00] Walter Bagehot. The english constitution, volume 3. Kegan Paul, Trench, Trubner, 1900. ¨
[Ban98] Bela Ban. Design and implementation of a reliable group communication toolkit for java, 1998.
[BBRTP07] Roberto Baldoni, Marin Bertier, Michel Raynal, and Sara Tucci-Piergiovanni. Looking for a definition of dynamic distributed systems. In International Conference on Parallel Computing Technologies, pages 1–14. Springer, 2007.
[Bit] Bitcoin community. Bitcoin-core source code. https://github.com/bitcoin/bitcoin. Accessed: 2015-06-30.
[BJ87] Ken Birman and Thomas Joseph. Exploiting virtual synchrony in distributed systems. volume 21. ACM, 1987.
[BMC+15] Joseph Bonneau, Andrew Miller, Jeremy Clark, Arvind Narayanan, Joshua A Kroll, and Edward W Felten. Sok: Research perspectives and challenges for bitcoin and cryptocurrencies. In IEEE Symposium on Security and Privacy, 2015.
[BO83] Michael Ben-Or. Another advantage of free choice (extended abstract): Completely asynchronous agreement protocols. In Proceedings of the second annual ACM symposium on Principles of distributed computing, pages 27–30. ACM, 1983.
[BPS16a] Iddo Bentov, Rafael Pass, and Elaine Shi. The sleepy model of consensus. https://eprint.iacr.org/2016/918.pdf, 2016. Accessed: 2016-11-08.
[BPS16b] Iddo Bentov, Rafael Pass, and Elaine Shi. Snow white: Provably secure proofs of stake. https://eprint.iacr.org/2016/919.pdf, 2016. Accessed: 2016-11-08.
[BR09] Franc¸ois Bonnet and Michel Raynal. The price of anonymity: Optimal consensus despite asynchrony, crash and anonymity. In Proceedings of the 23rd international conference on Distributed computing, pages 341–355. Springer-Verlag, 2009.
[Bre00] EA Brewer. Towards robust distributed systems. abstract. In Proceedings of the Nineteenth Annual ACM Symposium on Principles of Distributed Computing, page 7, 2000.
[BSAB+17] Shehar Bano, Alberto Sonnino, Mustafa Al-Bassam, Sarah Azouvi, Patrick McCorry, Sarah Meiklejohn, and George Danezis. Consensus in the age of blockchains. arXiv:1711.03936, 2017. Accessed:2017-12-11.
[BT16] Zohir Bouzid and Corentin Travers. Anonymity-preserving failure detectors. In International Symposium on Distributed Computing, pages 173–186. Springer, 2016.
[Can00] Ran Canetti. Security and composition of multiparty cryptographic protocols. Journal of CRYPTOLOGY, 13(1):143–202, 2000.
[Can01] Ran Canetti. Universally composable security: A new paradigm for cryptographic protocols. In Foundations of Computer Science, 2001. Proceedings. 42nd IEEE Symposium on, pages 136–145. IEEE, 2001.
[CFN90] David Chaum, Amos Fiat, and Moni Naor. Untraceable electronic cash. In Proceedings on Advances in cryptology, pages 319–327. Springer-Verlag New York, Inc., 1990.
[CGR07] Tushar D Chandra, Robert Griesemer, and Joshua Redstone. Paxos made live: an engineering perspective. In Proceedings of the twenty-sixth annual ACM symposium on Principles of distributed computing, pages 398–407. ACM, 2007.
[CGR11] Christian Cachin, Rachid Guerraoui, and Luis Rodrigues. Introduction to reliable and secure distributed programming. Springer Science & Business Media, 2011.
[CKS00] Christian Cachin, Klaus Kursawe, and Victor Shoup. Random oracles in constantinople: Practical asynchronous byzantine agreement using cryptography. In Proceedings of the nineteenth annual ACM symposium on Principles of distributed computing, pages 123–132. ACM, 2000.
[CL+99] Miguel Castro, Barbara Liskov, et al. Practical byzantine fault tolerance. In OSDI, volume 99, pages 173–186, 1999.
[CL02] Miguel Castro and Barbara Liskov. Practical byzantine fault tolerance and proactive recovery. ACM Transactions on Computer Systems (TOCS), 20(4):398–461, 2002.
[CNV04] Miguel Correia, Nuno Ferreira Neves, and Paulo Verissimo. How to tolerate half less one byzantine nodes in practical distributed systems. In Reliable Distributed Systems, 2004. Proceedings of the 23rd IEEE International Symposium on, pages 174–183. IEEE, 2004.
[Coo09] J. L. Coolidge. The gambler’s ruin. Annals of Mathematics, 10(4):181–192, 1909.
[Cri91] Flaviu Cristian. Reaching agreement on processor-group membrship in synchronous distributed systems. Distributed Computing, 4(4):175–187, 1991.
[CT96] Tushar Deepak Chandra and Sam Toueg. Unreliable failure detectors for reliable distributed systems. volume 43, pages 225–267. ACM, 1996.
[CV17] Christian Cachin and Marko Vukolic. Blockchain con- ´sensus protocols in the wild. arXiv:1707.01873, 2017. Accessed:2017-09-26.
[CVL10] Miguel Correia, Giuliana S Veronese, and Lau Cheuk Lung. Asynchronous byzantine consensus with 2f+ 1 processes. In Proceedings of the 2010 ACM symposium on applied computing, pages 475–480. ACM, 2010.
[CVNV11] Miguel Correia, Giuliana Santos Veronese, Nuno Ferreira Neves, and Paulo Verissimo. Byzantine consensus in asynchronous message-passing systems: a survey. volume 2, pages 141–161. Inderscience Publishers, 2011.
[CWA+09] Allen Clement, Edmund L Wong, Lorenzo Alvisi, Michael Dahlin, and Mirco Marchetti. Making byzantine fault tolerant systems tolerate byzantine faults. In NSDI, volume 9, pages 153–168, 2009.
[DDS87] Danny Dolev, Cynthia Dwork, and Larry Stockmeyer. On the minimal synchronism needed for distributed consensus. volume 34, pages 77–97. ACM, 1987.
[Dei] Wei Dei. b-money. http://www.weidai.com/bmoney.txt. Accessed on 03/03/2017.
[DGFGK10] Carole Delporte-Gallet, Hugues Fauconnier, Rachid Guerraoui, and Anne-Marie Kermarrec. Brief announcement: Byzantine agreement with homonyms. In Proceedings of the twentysecond annual ACM symposium on Parallelism in algorithms and architectures, pages 74–75. ACM, 2010.
[DGG02] Assia Doudou, Benoˆıt Garbinato, and Rachid Guerraoui. Encapsulating failure detection: From crash to byzantine failures. In International Conference on Reliable Software Technologies, pages 24–50. Springer, 2002.
[DGKR17] Bernardo David, Peter Gazi, Aggelos Kiayias, and Alexan- ˇder Russell. Ouroboros praos: An adaptively-secure, semisynchronous proof-of-stake protocol. Cryptology ePrint Archive, Report 2017/573, 2017. Accessed: 2017-06-29.
[DLP+86] Danny Dolev, Nancy A Lynch, Shlomit S Pinter, Eugene W Stark, and William E Weihl. Reaching approximate agreement in the presence of faults. volume 33, pages 499–516. ACM, 1986.
[DLS88] Cynthia Dwork, Nancy Lynch, and Larry Stockmeyer. Consensus in the presence of partial synchrony. volume 35, pages 288–323. ACM, 1988.
[DN92] Cynthia Dwork and Moni Naor. Pricing via processing or combatting junk mail. In Annual International Cryptology Conference, pages 139–147. Springer, 1992.
[Dol81] Danny Dolev. Unanimity in an unknown and unreliable environment. In Foundations of Computer Science, 1981. SFCS’81. 22nd Annual Symposium on, pages 159–168. IEEE, 1981.
[Dou02] John R Douceur. The sybil attack. In International Workshop on Peer-to-Peer Systems, pages 251–260. Springer, 2002.
[DSU04] Xavier Defago, Andr ´ e Schiper, and P ´ eter Urb ´ an. Total order ´ broadcast and multicast algorithms: Taxonomy and survey. ACM Computing Surveys (CSUR), 36(4):372–421, 2004.
[DW13] Christian Decker and Roger Wattenhofer. Information propagation in the bitcoin network. In Peer-to-Peer Computing (P2P), 2013 IEEE Thirteenth International Conference on, pages 1–10. IEEE, 2013.
[EGSvR16] Ittay Eyal, Adem Efe Gencer, Emin Gun Sirer, and Robbert van Renesse. Bitcoin-ng: A scalable blockchain protocol. In 13th USENIX Security Symposium on Networked Systems Design and Implementation (NSDI’16). USENIX Association, Mar 2016.
[ES14] Ittay Eyal and Emin Gun Sirer. Majority is not enough: Bitcoin ¨ mining is vulnerable. In Financial Cryptography and Data Security, pages 436–454. Springer, 2014.
[Fin04] Hal Finney. Reusable proofs of work (rpow). http://web.archive.org/web/20071222072154/http://rpow.net/, 2004. Accessed: 2016-04-31.
[Fis83] Michael J Fischer. The consensus problem in unreliable distributed systems (a brief survey). In International Conference on Fundamentals of Computation Theory, pages 127–140. Springer, 1983.
[FL82] Michael J FISCHER and Nancy A LYNCH. A lower bound for the time to assure interactive consistency. volume 14, Jun 1982.
[FLP85] Michael J Fischer, Nancy A Lynch, and Michael S Paterson. Impossibility of distributed consensus with one faulty process. volume 32, pages 374–382. ACM, 1985.
[Fuz08] Rachele Fuzzati. A formal approach to fault tolerant distributed consensus. PhD thesis, EPFL, 2008.
[GHM+17] Yossi Gilad, Rotem Hemo, Silvio Micali, Georgios Vlachos, and Nickolai Zeldovich. Algorand: Scaling byzantine agreements for cryptocurrencies. Cryptology ePrint Archive, Report 2017/454, 2017. Accessed: 2017-06-29.
[GKL15] Juan Garay, Aggelos Kiayias, and Nikos Leonardos. The bitcoin backbone protocol: Analysis and applications. In Advances in Cryptology-EUROCRYPT 2015, pages 281–310. Springer, 2015.
[GKL16] Juan A. Garay, Aggelos Kiayias, and Nikos Leonardos. The bitcoin backbone protocol with chains of variable difficulty. http://eprint.iacr.org/2016/1048.pdf, 2016. Accessed: 2017-02-06.
[GKP17] Juan A. Garay, Aggelos Kiayias, and Giorgos Panagiotakos. Proofs of work for blockchain protocols. Cryptology ePrint Archive, Report 2017/775, 2017. http://eprint.iacr.org/2017/775.
[GKQV10] Rachid Guerraoui, Nikola Knezevi ˇ c, Vivien Qu ´ ema, and Marko ´ Vukolic. The next 700 bft protocols. In ´ Proceedings of the 5th European conference on Computer systems, pages 363–376. ACM, 2010.
[GKTZ12] Adam Groce, Jonathan Katz, Aishwarya Thiruvengadam, and Vassilis Zikas. Byzantine agreement with a rational adversary. pages 561–572. Springer, 2012.
[GKW+16] Arthur Gervais, Ghassan O Karame, Karl Wust, Vasileios ¨ Glykantzis, Hubert Ritzdorf, and Srdjan Capkun. On the security and performance of proof of work blockchains. https://eprint.iacr.org/2016/555.pdf, 2016. Accessed: 2016-08-10.
[GL02] Seth Gilbert and Nancy Lynch. Brewer’s conjecture and the feasibility of consistent, available, partition-tolerant web services. volume 33, pages 51–59. ACM, 2002.
[GRKC15] Arthur Gervais, Hubert Ritzdorf, Ghassan O Karame, and Srdjan Capkun. Tampering with the delivery of blocks and transactions in bitcoin. In Proceedings of the 22nd ACM SIGSAC Conference on Computer and Communications Security, pages 692–705. ACM, 2015.
[Her88] Maurice P Herlihy. Impossibility and universality results for wait-free synchronization. In Proceedings of the seventh annual ACM Symposium on Principles of distributed computing, pages 276–290. ACM, 1988.
[Her91] Maurice Herlihy. Wait-free synchronization. ACM Transactions on Programming Languages and Systems (TOPLAS), 13(1):124–149, 1991.
[HKZG15] Ethan Heilman, Alison Kendler, Aviv Zohar, and Sharon Goldberg. Eclipse attacks on bitcoin’s peer-to-peer network. In 24th USENIX Security Symposium (USENIX Security 15), pages 129–144, 2015.
[Hoe07] Jaap-Henk Hoepman. Distributed double spending prevention. In Security Protocols Workshop, pages 152–165. Springer, 2007.
[HT94] Vassos Hadzilacos and Sam Toueg. A modular approach to fault-tolerant broadcasts and related problems. Cornell University Technical Report 94-1425, 1994.
[IT08] Hideaki Ishii and Roberto Tempo. Las vegas randomized algorithms in distributed consensus problems. In 2008 American Control Conference, pages 2579–2584. IEEE, 2008.
[JB99] Ari Juels and John G Brainard. Client puzzles: A cryptographic countermeasure against connection depletion attacks. In NDSS, volume 99, pages 151–165, 1999.
[KMMS01] Kim Potter Kihlstrom, Louise E Moser, and P Michael MelliarSmith. The securering group communication system. ACM Transactions on Information and System Security (TISSEC), 4(4):371–406, 2001.
[KMMS03] Kim Potter Kihlstrom, Louise E Moser, and P Michael MelliarSmith. Byzantine fault detectors for solving consensus. volume 46, pages 16–35. Br Computer Soc, 2003.
[KMTZ13] Jonathan Katz, Ueli Maurer, Bjorn Tackmann, and Vassilis ¨ Zikas. Universally composable synchronous computation. In TCC, volume 7785, pages 477–498. Springer, 2013.
[KP15] Aggelos Kiayias and Giorgos Panagiotakos. Speed-security tradeoff s in blockchain protocols. https://eprint.iacr.org/2015/1019.pdf, Oct 2015. Accessed: 2016-10-17.
[KP16] Aggelos Kiayias and Giorgos Panagiotakos. On trees, chains and fast transactions in the blockchain. http://eprint.iacr.org/2016/545.pdf, 2016. Accessed: 2017-02-06.
[KRDO16] Aggelos Kiayias, Alexander Russell, Bernardo David, and Roman Oliynykov. Ouroboros: A provably secure proof-of-stake blockchain protocol. https://pdfs.semanticscholar.org/1c14/549f7ba7d6a000d79a7d12255eb11113e6fa.pdf, 2016. Accessed: 2017-02-20.
[Lam84] Leslie Lamport. Using time instead of timeout for fault-tolerant distributed systems. volume 6, pages 254–280. ACM, 1984.
[Lam98] Leslie Lamport. The part-time parliament. volume 16, pages 133–169. ACM, 1998.
[LCW+06] Harry C Li, Allen Clement, Edmund L Wong, Jeff Napper, Indrajit Roy, Lorenzo Alvisi, and Michael Dahlin. Bar gossip. In Proceedings of the 7th symposium on Operating systems design and implementation, pages 191–204. USENIX Association, 2006.
[LSM06] Brian Neil Levine, Clay Shields, and N Boris Margolin. A survey of solutions to the sybil attack. University of Massachusetts Amherst, Amherst, MA, 7, 2006.
[LSP82] Leslie Lamport, Robert Shostak, and Marshall Pease. The byzantine generals problem. volume 4, pages 382–401. ACM, 1982.
[LSZ15] Yoad Lewenberg, Yonatan Sompolinsky, and Aviv Zohar. Inclusive block chain protocols. In Financial Cryptography and Data Security, pages 528–547. Springer, 2015.
[LTKS15] Loi Luu, Jason Teutsch, Raghav Kulkarni, and Prateek Saxena. Demystifying incentives in the consensus computer. In Proceedings of the 22nd ACM SIGSAC Conference on Computer and Communications Security, pages 706–719. ACM, 2015.
[Lyn96] Nancy A Lynch. Distributed algorithms. Morgan Kaufmann, 1996.
[Mic16] Silvio Micali. Algorand: The efficient and democratic ledger. http://arxiv.org/abs/1607.01341, 2016. Accessed: 2017-02-09.
[Mic17] Silvio Micali. Byzantine agreement, made trivial. https://people.csail.mit.edu/silvio/SelectedApr 2017. Accessed:2018-02-21.
[MJ14] A Miller and LaViola JJ. Anonymous byzantine consensus from moderately-hard puzzles: A model for bitcoin. https://socrates1024.s3.amazonaws.com/consensus.pdf, 2014. Accessed: 2016-03-09.
[MMRT03] Dahlia Malkhi, Michael Merritt, Michael K Reiter, and Gadi Taubenfeld. Objects shared by byzantine processes. volume 16, pages 37–48. Springer, 2003.
[MPR01] Hugo Miranda, Alexandre Pinto, and Luıs Rodrigues. Appia, a flexible protocol kernel supporting multiple coordinated channels. In Distributed Computing Systems, 2001. 21st International Conference on., pages 707–710. IEEE, 2001.
[MR97] Dahlia Malkhi and Michael Reiter. Unreliable intrusion detection in distributed computations. In Computer Security Foundations Workshop, 1997. Proceedings., 10th, pages 116–124. IEEE, 1997.
[MRT00] Achour Mostefaoui, Michel Raynal, and Fred´ eric Tronel. From ´ binary consensus to multivalued consensus in asynchronous message-passing systems. Information Processing Letters, 73(5-6):207–212, 2000.
[MXC+16] Andrew Miller, Yu Xia, Kyle Croman, Elaine Shi, and Dawn Song. The honey badger of bft protocols. https://eprint.iacr.org/2016/199.pdf, 2016. Accessed: 2017-01-10.
[Nak08a] Satoshi Nakamoto. Bitcoin: A peer-to-peer electronic cash system. https://bitcoin.org/bitcoin.pdf, Dec 2008. Accessed: 2015-07-01.
[Nak08b] Satoshi Nakamoto. Bitcoin p2p e-cash paper, 2008.
[Nar16] Narayanan, Arvind and Bonneau, Joseph and Felten, Edward and Miller, Andrew and Goldfeder, Steven. Bitcoin and cryptocurrency technologies. https://d28rh4a8wq0iu5.cloudfront.net/bitcointech/readings/princeton bitcoin book.pdf?a=1, 2016. Accessed: 2016-03-29.
[Nei94] Gil Neiger. Distributed consensus revisited. Information processing letters, 49(4):195–201, 1994.
[NG16] Christopher Natoli and Vincent Gramoli. The blockchain anomaly. In Network Computing and Applications (NCA), 2016 IEEE 15th International Symposium on, pages 310–317. IEEE, 2016.
[NKMS16] Kartik Nayak, Srijan Kumar, Andrew Miller, and Elaine Shi. Stubborn mining: Generalizing selfish mining and combining with an eclipse attack. In 1st IEEE European Symposium on Security and Privacy, 2016. IEEE, 2016.
[PS16a] Rafael Pass and Elaine Shi. Fruitchains: A fair blockchain. http://eprint.iacr.org/2016/916.pdf, 2016. Accessed: 2016-11-08.
[PS16b] Rafael Pass and Elaine Shi. Hybrid consensus: Scalable permissionless consensus. https://eprint.iacr.org/2016/917.pdf, Sep 2016. Accessed: 2016-10-17.
[PS17] Rafael Pass and Elaine Shi. Thunderella: Blockchains with optimistic instant confirmation. Cryptology ePrint Archive, Report 2017/913, 2017. Accessed:2017-09-26.
[PSL80] Marshall Pease, Robert Shostak, and Leslie Lamport. Reaching agreement in the presence of faults. volume 27, pages 228–234. ACM, 1980.
[PSs16] Rafael Pass, Lior Seeman, and abhi shelat. Analysis of the blockchain protocol in asynchronous networks. http://eprint.iacr.org/2016/454.pdf, 2016. Accessed: 2016-08-01.
[Rab83] Michael O Rabin. Randomized byzantine generals. In Foundations of Computer Science, 1983., 24th Annual Symposium on, pages 403–409. IEEE, 1983.
[Rei96] Michael K Reiter. A secure group membership protocol. volume 22, page 31, 1996.
[Ric93] Aleta M Ricciardi. The group membership problem in asynchronous systems. PhD thesis, Cornell University, 1993.
[Ros14] M. Rosenfeld. Analysis of hashrate-based double spending. http://arxiv.org/abs/1402.2009, 2014. Accessed: 2016-03-09.
[RSW96] Ronald L Rivest, Adi Shamir, and David A Wagner. Time-lock puzzles and timed-release crypto. 1996.
[Sch90] Fred B Schneider. Implementing fault-tolerant services using the state machine approach: A tutorial. volume 22, pages 299–319. ACM, 1990.
[SLZ16] Yonatan Sompolinsky, Yoad Lewenberg, and Aviv Zohar. Spectre: A fast and scalable cryptocurrency protocol. Cryptology ePrint Archive, Report 2016/1159, 2016. Accessed: 2017-02-20.
[SSZ15] Ayelet Sapirshtein, Yonatan Sompolinsky, and Aviv Zohar. Optimal selfish mining strategies in bitcoin. http://arxiv.org/pdf/1507.06183.pdf, 2015. Accessed: 2016-08-22.
[SW16] David Stolz and Roger Wattenhofer. Byzantine agreement with median validity. In LIPIcs-Leibniz International Proceedings in Informatics, volume 46. Schloss Dagstuhl-Leibniz-Zentrum fuer Informatik, 2016.
[Swa15] Tim Swanson. Consensus-as-a-service: a brief report on the emergence of permissioned, distributed ledger systems. http://www.ofnumbers.com/wp-content/uploads/2015/04/Permissioned-distributed-ledgers.pdf, Apr 2015. Accessed: 2017-10-03.
[SZ13] Yonatan Sompolinsky and Aviv Zohar. Accelerating bitcoin’s transaction processing. fast money grows on trees, not chains, 2013.
[SZ16] Yonatan Sompolinsky and Aviv Zohar. Bitcoin’s security model revisited. http://arxiv.org/pdf/1605.09193, 2016. Accessed: 2016-07-04.
[Sza14] Nick Szabo. The dawn of trustworthy computing. http://unenumerated.blogspot.co.at/2014/12/the-dawn-of-trustworthy-computing.html, 2014. Accessed: 2017-12-01.
[TS16] Florian Tschorsch and Bjorn Scheuermann. Bitcoin and ¨ beyond: A technical survey on decentralized digital currencies. In IEEE Communications Surveys Tutorials, volume PP, pages 1–1, 2016.
[VCB+13] Giuliana Santos Veronese, Miguel Correia, Alysson Neves Bessani, Lau Cheuk Lung, and Paulo Verissimo. Efficient byzantine fault-tolerance. volume 62, pages 16–30. IEEE, 2013.
[Ver03] Paulo Ver´ıssimo. Uncertainty and predictability: Can they be reconciled? In Future Directions in Distributed Computing, pages 108–113. Springer, 2003.
[Vuk15] Marko Vukolic. The quest for scalable blockchain fabric: ´ Proof-of-work vs. bft replication. In International Workshop on Open Problems in Network Security, pages 112–125. Springer, 2015.
[Vuk16] Marko Vukolic. Eventually returning to strong consistency. https://pdfs.semanticscholar.org/a6a1/b70305b27c556aac779fb65429db9c2e1ef2.pdf, 2016. Accessed: 2016-08-10.
[XWS+17] Xiwei Xu, Ingo Weber, Mark Staples, Liming Zhu, Jan Bosch, Len Bass, Cesare Pautasso, and Paul Rimba. A taxonomy of blockchain-based systems for architecture design. In Software Architecture (ICSA), 2017 IEEE International Conference on , pages 243–252. IEEE, 2017.
[YHKC+16] Jesse Yli-Huumo, Deokyoon Ko, Sujin Choi, Sooyong Park, and Kari Smolander. Where is current research on blockchain technology? – a systematic review. volume 11, page e0163477. Public Library of Science, 2016.
[ZP17] Ren Zhang and Bart Preneel. On the necessity of a prescribed block validity consensus: Analyzing bitcoin unlimited mining protocol. http://eprint.iacr.org/2017/686, 2017. Accessed: 2017-07-20.
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O Preço do Bitcoin pode chegar a 98500 dólares segundo analistas de Wall Street

O preço do bitcoin pode subir para até $ 98.500, de acordo com analistas da empresa de serviços financeiros e de investimentos Wedbush Securities.
Um relatório dos analistas Gil Luria e Aron Turner, que tem sido referenciado em StreetInsider.com, tem uma visão extremamente positiva do bitcoin, sugerindo que a moeda digital tem o potencial de sacudir o espaço de pagamentos atual.
Intitulado Bitcoin: O Valor Intrínseco Como Um Canal Para Rede de Tecnologia Disruptiva De Pagamento, o relatório afirma:
"Entre outras facetas, acreditamos que o bitcoin e a tecnologia associada à ele representam uma potencial ruptura que mudará o jogo para as nossas empresas de pagamento."
Os autores argumentam ainda cryptomoeda oferece uma "alternativa poderosa para redes de marca", devido ao seu processamento descentralizado, novas funcionalidades e utilização de taxas baseadas no mercado.
O preço do bitcoin tem sido um Hot Topic desde a semana passada, com a moeda digital aumentando para os vertiginosos US$ 1165 no sábado, de acordo com theCoinDesk BPI. Em Mt. Gox, o preço superou US$ 1242, ultrapassando o preço do ouro pela primeira vez (o ouro estava em 1241 dólares por onça).
Erik Voorhees, que vendeu o site de apostas SatoshiDice por 126.315 BTC este ano, disse que isto mostrou em que "trunfo respeitável" o bitcoin está se tornando.
"Claramente, o Bitcoin não é mais só uma moeda insignificante. Ele está jogando na grande liga - valendo mais do que uma parte do Google ou da Apple, e até mesmo mais do que uma onça de ouro", disse ele na época.
O valor tem flutuado nestes últimos dias, com o preço, no momento da escrita deste artigo, pairando em torno de US$ 1071.
Sobe ou desce?
Muitas pessoas têm afirmado que o valor alto atual é meramente um aumento temporário e que em breve cairá para o mesmo nível observado em setembro e outubro (cerca de US $ 120 - $ 150), ou talvez ainda mais baixos.
Luria e Turner discordam, acreditando que o valor vai continuar a aumentar nos próximos anos. Eles disseram:
"Acreditamos que a subida dos preços do bitcoin ajudou a construir a rede, e assim, consolidando o seu valor, especialmente vis-à-vis outras moedas alternativas. Com base neste quadro, nós postulamos que os preços atuais refletem um auge de 1% do total da demanda potencial do Bitcoin em 10 anos".
No mês passado, os gêmeos Winklevoss comentaram que eles previam um aumento de 100 vezes no preço do Bitcoin. Na época de seus comentários, o preço do bitcoin foi de US $ 343 de modo que o valor já aumentou mais de 211%.
Falando à CNBC na conferência Dealbook em Nova York, Tyler Winklevoss, que estava envolvido na criação do Facebook, disse: "Algumas pessoas definitivamente o veem [bitcoin] como um Ouro 2.0".
Os Milhões de Clamath
Ex-executivo do Facebook, Chamath Palihapitiya, também é muito otimista a respeito do bitcoin.
No final de outubro, ele revelou que possuía US$ 5 milhões no valor da moeda digital, mas disse que estava esperando para alcançar cerca de 10-15 milhões de dólares com ela. Em 29 de outubro, o preço do bitcoin foi ligeiramente inferior a US $ 200, por isso é provável que ele tinha cerca de 25.000 BTC. Essa quantidade de bitcoins agora vale mais de US $ 26 milhões, por isso parece que Palihapitiya conseguiu o que desejava e um pouco mais.
Em maio, ele escreveu um artigo para a Bloomberg afirmando que o Bitcoin pode se tornar uma "versão melhorada" do ouro, ou mesmo um substituto para o metal precioso. Com todo o ouro do mundo totalizando aproximadamente US $ 8 trilhões, Palihapitiya disse que se o bitcoin substituisse o ouro como reserva de valor cada bitcoin custaria quase $ 400.000, uma vez que todos os 21 milhões de bitcoins fossem minados (US $ 8 trilhões/21milhões BTC).
"Se o Bitcoin se tornar algo maior - uma moeda de reserva útil, então cuidado: Seu valor será muito superior $ 400.000", escreveu ele, acrescentando:
"Eu pessoalmente acho que o Bitcoin já é superior ao ouro. O seu papel como moeda ainda está para ser determinado, mas ao longo da próxima década, ser o Ouro 2.0 será suficiente, considerando que isso representaria um retorno de mais de 3.000 vezes".
O problema com a volatilidade
Enquanto muitas pessoas acreditam que, a longo prazo, o preço do bitcoin será consideravelmente maior do que é agora, a visão comum é que a sua volatilidade continuará no curto prazo.
Luria e Turner explicaram em seu relatório que esta volatilidade é o resultado de um "processo de descoberta de preço estendida". Acredita-se quanto maiores forem os ganhos líquidos do bitcoin e quanto mais ele for amplamente aprovado, maior a probabilidade de se estabilizar o seu preço.
Atualmente, a volatilidade da moeda é o fator que está fazendo com que um alto percentual de pessoas leve o bitcoin a sério.
Na Universidade da Califórnia em San Diego, a pesquisadora Sarah Meiklejohn, que escreveu um artigo chamado Um Punhado DE Bitcoins: Caracterizando Pagamentos Entre Homens Sem Nome, disse ao CoinDesk que a coisa que a deixa "mais nervosa" a respeito do bitcoin é a sua volatilidade .
"É um problema do tipo galinha ou ovo. Você precisa de mais pessoas adotando o bitcoin a fim de estabilizar isso, mas as pessoas estão se afastando porque elas o veem como volátil e como um investimento de risco", disse ela.
A solução para este problema ainda não está claro, mas a comunidade bitcoin e os negócios dentro dele continuam a trabalhar arduamente para tornar mais fácil para os comerciantes aceitar bitcoins e para os consumidores obtê-los e em seguida gastá-los.
Qual você acha que é a chave para a estabilidade do bitcoin?
Traduzido por Sarah Alexandre Original em: http://www.coindesk.com/bitcoin-price-reach-98500-say-wall-street-analysts/
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A Bitcoin-Style Currency for Central Banks: The Bank of England asked researchers to invent a digital currency with a more centralized design.

This is an automatic summary, original reduced by 70%.
Now researchers have invented a Bitcoin-like system that could make digital cash more practical by allowing a central bank such as the Federal Reserve to control it.
The system, RSCoin, was designed by researchers Sarah Meiklejohn and George Danezis at University College London, at the suggestion of the U.K.'s central bank, the Bank of England.
RSCoin's ledger is solely in the hands of the central bank, which would also retain a special encryption key that could be used to control the money supply-for example, to take actions like the quantitative easing programs the Federal Reserve and other central banks put in place after the 2008 financial crisis.
A small collection of third-party organizations would be chosen by the central bank to process new transactions and submit them for inclusion in the central ledger.
Bhagwan Chowdhry, a professor of finance at UCLA, says that by adopting a system like RSCoin, central banks could enable the financial system to serve people much better.
One reason a central bank might like a digital currency is that its ledger provides a very detailed record of financial activity.
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One America News Investigates: Biden’s Bribe Tapes - PART 2 MONUMENTAL BITCOIN CHART NOBODY IS WATCHING RIGHT NOW (btc crypto live market news analysis today ta Todays Message: See from a higher perspective 07-10-20_Sarah_Mike Shannon_Zoey_wait heel come and place command Panel: Technical Challenges: Blockchain Scalability and Others - Blockchain Workshops - Sydney 2015

Sarah Meiklejohn, a computer scientist at University College London, said that when Bitcoin first emerged, law enforcement officials were terrified. However, as forensic technologies have caught up, the means to track criminals now exist. NewsBTC is a news service that covers bitcoin news, technical analysis & forecasts for bitcoin and With academic research on Bitcoin and cryptocurrencies still in its infancy, Sarah Meiklejohn's track record of publications in the area stands out. The UCL computer science professor has explored topics ranging from anonymity in Bitcoin to how a central bank could go about issuing a cryptocurrency. Topics covered included: What techniques can be used to deanonymize Bitcoin users How Bitcoin's That’s according to Sarah Meiklejohn, a computer scientist at University College London. What Meiklejohn said is that the introduction of bitcoin initially sprouted fear within the law University of California, San Diego researcher Sarah Meiklejohn recently completed a paper that traced the movements of bitcoin in April using heuristics, a specific problem-solving technique that I asked Sarah Meiklejohn, a computer scientist at the University of California, San Diego, for her thoughts. Meiklejohn says that that 194,993-bitcoin transaction was probably done by Bitstamp

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One America News Investigates: Biden’s Bribe Tapes - PART 2

BITCOIN HALVING IS ABOUT TO SHAKE THE CRYPTO MARKET (btc crypto live price analysis news today 2020 - Duration: 54:56. Crypto Crew University 33,405 views 54:56 Support the show, consider donating: 1MjytrKGNVYkqPfmBKrm3MJzm36vH6m8ZR (http://bit.ly/2bNodUa) With academic research on Bitcoin and cryptocurrencies still ... CNBC's Bob Pisani reports on where bitcoin could go from its recent new high. » Subscribe to CNBC: http://cnb.cx/SubscribeCNBC About CNBC: From 'Wall Street'... Please LIKE - SHARE - COMMENT - SUBSCRIBE - SUPPORT thank you, namaste Please consider supporting this page so that I can continue to bring these and all the other free messages through to ... Seminar with Sarah Meiklejohn at University College London 16th October 2014 Link to Research Paper: A Fistful of Bitcoins: Characterizing Payments Among

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