Divesh Aggarwal, G. Brennen, Troy Lee, M. Santha, M. Tomamichel
The key cryptographic protocols used to secure the internet and financial transactions of today are all susceptible to attack by the development of a sufficiently large quantum computer. One particular area at risk is cryptocurrencies, a market currently worth over 100 billion USD. We investigate the risk posed to Bitcoin, and other cryptocurrencies, by attacks using quantum computers. We find that the proof-of-work used by Bitcoin is relatively resistant to substantial speedup by quantum computers in the next 10 years, mainly because specialized ASIC miners are extremely fast compared to the estimated clock speed of near-term quantum computers. On the other hand, the elliptic curve signature scheme used by Bitcoin is much more at risk, and could be completely broken by a quantum computer as early as 2027, by the most optimistic estimates. We analyze an alternative proof-of-work called Momentum, based on finding collisions in a hash function, that is even more resistant to speedup by a quantum computer. We also review the available post-quantum signature schemes to see which one would best meet the security and efficiency requirements of blockchain applications.
{"title":"Quantum Attacks on Bitcoin, and How to Protect Against Them","authors":"Divesh Aggarwal, G. Brennen, Troy Lee, M. Santha, M. Tomamichel","doi":"10.5195/ledger.2018.127","DOIUrl":"https://doi.org/10.5195/ledger.2018.127","url":null,"abstract":"The key cryptographic protocols used to secure the internet and financial transactions of today are all susceptible to attack by the development of a sufficiently large quantum computer. One particular area at risk is cryptocurrencies, a market currently worth over 100 billion USD. We investigate the risk posed to Bitcoin, and other cryptocurrencies, by attacks using quantum computers. We find that the proof-of-work used by Bitcoin is relatively resistant to substantial speedup by quantum computers in the next 10 years, mainly because specialized ASIC miners are extremely fast compared to the estimated clock speed of near-term quantum computers. On the other hand, the elliptic curve signature scheme used by Bitcoin is much more at risk, and could be completely broken by a quantum computer as early as 2027, by the most optimistic estimates. We analyze an alternative proof-of-work called Momentum, based on finding collisions in a hash function, that is even more resistant to speedup by a quantum computer. We also review the available post-quantum signature schemes to see which one would best meet the security and efficiency requirements of blockchain applications.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2017-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42239134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a simple game theoretic framework, assuming complete information, to model Bitcoin mining activity. It does so by formalizing the activity as an all-pay contest: a competition where participants contend with each other to win a prize by investing in computational power, and victory is probabilistic. With at least two active miners, the unique pure strategy Nash equilibrium of the game suggests the following interesting insights on the motivation for being a miner: while the optimal amount of energy consumption depends also on the reward for solving the puzzle, as long as the reward is positive the decision to be an active miner depends only on the mining costs. Moreover, the intrinsic structure of the mining activity seems to prevent the formation of a monopoly, because in an equilibrium with two miners, both of them will have positive expected profits for any level of the opponent’s costs. A monopoly could only form if the rate of return on investment were higher outside bitcoin.
{"title":"Bitcoin Mining as a Contest","authors":"N. Dimitri","doi":"10.5195/LEDGER.2017.96","DOIUrl":"https://doi.org/10.5195/LEDGER.2017.96","url":null,"abstract":"This paper presents a simple game theoretic framework, assuming complete information, to model Bitcoin mining activity. It does so by formalizing the activity as an all-pay contest: a competition where participants contend with each other to win a prize by investing in computational power, and victory is probabilistic. With at least two active miners, the unique pure strategy Nash equilibrium of the game suggests the following interesting insights on the motivation for being a miner: while the optimal amount of energy consumption depends also on the reward for solving the puzzle, as long as the reward is positive the decision to be an active miner depends only on the mining costs. Moreover, the intrinsic structure of the mining activity seems to prevent the formation of a monopoly, because in an equilibrium with two miners, both of them will have positive expected profits for any level of the opponent’s costs. A monopoly could only form if the rate of return on investment were higher outside bitcoin.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"2 1","pages":"31-37"},"PeriodicalIF":0.7,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41548191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Blockchains can be used to build multi-player online games and virtual worlds that require no central server. This concept is pioneered by Huntercoin, but it leads to large growth of the blockchain and heavy resource requirements. In this paper, we present a new protocol inspired by payment channels and sidechains that allows for trustless off-chain interactions of players in private turn-based games. They are usually performed without requiring space in the public blockchain, but if a dispute arises, the public network can be used to resolve the conflict. We also analyze the resulting security guarantees and describe possible extensions to games with shared turns and for near real-time interaction. Our proposed concept can be used to scale Huntercoin to very large or even infinite worlds and to enable almost real-time interactions between players.
{"title":"Game Channels for Trustless Off-Chain Interactions in Decentralized Virtual Worlds","authors":"Daniel Kraft","doi":"10.5195/LEDGER.2016.15","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.15","url":null,"abstract":"Blockchains can be used to build multi-player online games and virtual worlds that require no central server. This concept is pioneered by Huntercoin, but it leads to large growth of the blockchain and heavy resource requirements. In this paper, we present a new protocol inspired by payment channels and sidechains that allows for trustless off-chain interactions of players in private turn-based games. They are usually performed without requiring space in the public blockchain, but if a dispute arises, the public network can be used to resolve the conflict. We also analyze the resulting security guarantees and describe possible extensions to games with shared turns and for near real-time interaction. Our proposed concept can be used to scale Huntercoin to very large or even infinite worlds and to enable almost real-time interactions between players.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"54 96 1","pages":"84-98"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Orphan risk for large blocks limits Bitcoin’s transactional capacity while the lack of secure instant transactions restricts its usability. Progress on either front would help spur adoption. This paper considers a technique for using fractional-difficulty blocks (weak blocks) to build subchains bridging adjacent pairs of real blocks. Subchains reduce orphan risk by propagating blocks layer-by-layer over the entire block interval, rather than all at once when the proof-of-work is solved. Each new layer of transactions helps to secure the transactions included in lower layers, even though none of the transactions have been con-firmed in a real block. Miners are incentivized to cooperate building subchains in order to process more transactions per second (thereby claiming more fee revenue) without incur-ring additional orphan risk. The use of subchains also diverts fee revenue towards network hash power rather than dripping it out of the system to pay for orphaned blocks. By nesting subchains, weak block verification times approaching the theoretical limits imposed by speed-of-light constraints would become possible with future technology improvements. As subchains are built on top of the existing Bitcoin protocol, their implementation does not require any changes to Bitcoin’s consensus rules.
{"title":"Subchains: A Technique to Scale Bitcoin and Improve the User Experience","authors":"P. Rizun","doi":"10.5195/ledger.2016.40","DOIUrl":"https://doi.org/10.5195/ledger.2016.40","url":null,"abstract":"Orphan risk for large blocks limits Bitcoin’s transactional capacity while the lack of secure instant transactions restricts its usability. Progress on either front would help spur adoption. This paper considers a technique for using fractional-difficulty blocks (weak blocks) to build subchains bridging adjacent pairs of real blocks. Subchains reduce orphan risk by propagating blocks layer-by-layer over the entire block interval, rather than all at once when the proof-of-work is solved. Each new layer of transactions helps to secure the transactions included in lower layers, even though none of the transactions have been con-firmed in a real block. Miners are incentivized to cooperate building subchains in order to process more transactions per second (thereby claiming more fee revenue) without incur-ring additional orphan risk. The use of subchains also diverts fee revenue towards network hash power rather than dripping it out of the system to pay for orphaned blocks. By nesting subchains, weak block verification times approaching the theoretical limits imposed by speed-of-light constraints would become possible with future technology improvements. As subchains are built on top of the existing Bitcoin protocol, their implementation does not require any changes to Bitcoin’s consensus rules.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":"38-52"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We discuss the forging algorithm of Nxt from a probabilistic point of view, and obtain explicit formulas and estimates for several important quantities, such as the probability that an account generates a block, the length of the longest sequence of consecutive blocks generated by one account, and the probability that one concurrent blockchain wins over an- other one. Also, we discuss some attack vectors related to splitting an account into many smaller ones.
{"title":"A Probabilistic Analysis of the Nxt Forging Algorithm","authors":"S. Popov","doi":"10.5195/LEDGER.2016.46","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.46","url":null,"abstract":"We discuss the forging algorithm of Nxt from a probabilistic point of view, and obtain explicit formulas and estimates for several important quantities, such as the probability that an account generates a block, the length of the longest sequence of consecutive blocks generated by one account, and the probability that one concurrent blockchain wins over an- other one. Also, we discuss some attack vectors related to splitting an account into many smaller ones.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":"69-83"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article introduces a method of hiding transaction amounts in the strongly decentralized anonymous cryptocurrency Monero. Similar to Bitcoin, Monero is a cryptocurrency which is distributed through a proof-of-work “mining” process having no central party or trusted setup. The original Monero protocol was based on CryptoNote, which uses ring signatures and one-time keys to hide the destination and origin of transactions. Recently the technique of using a commitment scheme to hide the amount of a transaction has been discussed and implemented by Bitcoin Core developer Gregory Maxwell. In this article, a new type of ring signature, A Multilayered Linkable Spontaneous Anonymous Group signature is described which allows one to include a Pedersen Commitment in a ring signature. This construction results in a digital currency with hidden amounts, origins and destinations of transactions with reasonable efficiency and verifiable, trustless coin generation. The author would like to note that early drafts of this were publicized in the Monero Community and on the #bitcoin-wizards IRC channel. Blockchain hashed drafts are available showing that this work was started in Summer 2015, and completed in early October 2015. An eprint is also available at http://eprint.iacr.org/2015/1098 .
{"title":"Ring Confidential Transactions","authors":"Shen Noether, Adam Mackenzie","doi":"10.5195/LEDGER.2016.34","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.34","url":null,"abstract":"This article introduces a method of hiding transaction amounts in the strongly decentralized anonymous cryptocurrency Monero. Similar to Bitcoin, Monero is a cryptocurrency which is distributed through a proof-of-work “mining” process having no central party or trusted setup. The original Monero protocol was based on CryptoNote, which uses ring signatures and one-time keys to hide the destination and origin of transactions. Recently the technique of using a commitment scheme to hide the amount of a transaction has been discussed and implemented by Bitcoin Core developer Gregory Maxwell. In this article, a new type of ring signature, A Multilayered Linkable Spontaneous Anonymous Group signature is described which allows one to include a Pedersen Commitment in a ring signature. This construction results in a digital currency with hidden amounts, origins and destinations of transactions with reasonable efficiency and verifiable, trustless coin generation. The author would like to note that early drafts of this were publicized in the Monero Community and on the #bitcoin-wizards IRC channel. Blockchain hashed drafts are available showing that this work was started in Summer 2015, and completed in early October 2015. An eprint is also available at http://eprint.iacr.org/2015/1098 .","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":"1-18"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the widespread use of Internet, Web, and mobile technologies, a new category of applications and transactions that requires anonymity is gaining increased interest and importance. Examples of such new applications are innovative payment systems, digital notaries, electronic voting, documents sharing, electronic auctions, medical applications, and many others. In addition to anonymity, these applications and transactions also require standard security services: identification, authentication, and authorization of users and protection of their transactions. Providing those services in combination with anonymity is an especially challenging issue, because all security services require explicit user identification and authentication. To solve this issue and enable applications with security and also anonymity we introduce a new type of cryptographically encapsulated objects called BIX certificates. “BIX” is an abbreviation for “Blockchain Information Exchange.” Their purpose is equivalent to X.509 certificates: to support security services for users and transactions, but also enhanced with anonymity. This paper describes the structure and attributes of BIX certificate objects and all related protocols for their creation, distribution, and use. The BIX Certification Infrastructure (BCI) as a distributed public ledger is also briefly described.
{"title":"BIX Certificates: Cryptographic Tokens for Anonymous Transactions Based on Certificates Public Ledger","authors":"S. Muftic","doi":"10.5195/LEDGER.2016.27","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.27","url":null,"abstract":"With the widespread use of Internet, Web, and mobile technologies, a new category of applications and transactions that requires anonymity is gaining increased interest and importance. Examples of such new applications are innovative payment systems, digital notaries, electronic voting, documents sharing, electronic auctions, medical applications, and many others. In addition to anonymity, these applications and transactions also require standard security services: identification, authentication, and authorization of users and protection of their transactions. Providing those services in combination with anonymity is an especially challenging issue, because all security services require explicit user identification and authentication. To solve this issue and enable applications with security and also anonymity we introduce a new type of cryptographically encapsulated objects called BIX certificates. “BIX” is an abbreviation for “Blockchain Information Exchange.” Their purpose is equivalent to X.509 certificates: to support security services for users and transactions, but also enhanced with anonymity. This paper describes the structure and attributes of BIX certificate objects and all related protocols for their creation, distribution, and use. The BIX Certification Infrastructure (BCI) as a distributed public ledger is also briefly described.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":"19-37"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper discusses the game theory behind self-contained smart contract provably fair casinos, how they can be gamed by attackers with a large amount of money and computing power, as well as what are the necessary conditions to assure the system cannot be taken advantage of under various configurations.
{"title":"Gaming Self-Contained Provably Fair Smart Contract Casinos","authors":"Piotr J. Piasecki","doi":"10.5195/LEDGER.2016.29","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.29","url":null,"abstract":"This paper discusses the game theory behind self-contained smart contract provably fair casinos, how they can be gamed by attackers with a large amount of money and computing power, as well as what are the necessary conditions to assure the system cannot be taken advantage of under various configurations.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"21 1","pages":"99-110"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper is placed in the context of a growing number of social and political crit iq ues of blockchain technologies. We focus on the supposed potential of blockchain technologies to transform political institutions that are central to contemporary human societies, such as money, property right s regimes , and systems of democratic governance. Our aim is to examine the way blockchain technologies can bring about - and justify - new models of governance . To do so, w e draw on the philosophical works of Hobbes , Rousseau , and Rawls , analyzing blockchain governance in terms of contrasting social contract theories . We begin by comparing the justifications of blockchain governance offered by members of the blockchain developers ’ community with the justifications of governance presented with in social contract theories . We then examine the extent to which the model of governance offered by blockchain technologies reflect s key governance themes and assumptions located within social contract theories , focusing on the notions of sovereignty, the initial situation, decentralization and distributive justice .
{"title":"Governance in Blockchain Technologies & Social Contract Theories","authors":"Wessel Reijers, Fiachra O’Brolcháin, P. Haynes","doi":"10.5195/LEDGER.2016.62","DOIUrl":"https://doi.org/10.5195/LEDGER.2016.62","url":null,"abstract":"This paper is placed in the context of a growing number of social and political crit iq ues of blockchain technologies. We focus on the supposed potential of blockchain technologies to transform political institutions that are central to contemporary human societies, such as money, property right s regimes , and systems of democratic governance. Our aim is to examine the way blockchain technologies can bring about - and justify - new models of governance . To do so, w e draw on the philosophical works of Hobbes , Rousseau , and Rawls , analyzing blockchain governance in terms of contrasting social contract theories . We begin by comparing the justifications of blockchain governance offered by members of the blockchain developers ’ community with the justifications of governance presented with in social contract theories . We then examine the extent to which the model of governance offered by blockchain technologies reflect s key governance themes and assumptions located within social contract theories , focusing on the notions of sovereignty, the initial situation, decentralization and distributive justice .","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"1 1","pages":"134-151"},"PeriodicalIF":0.7,"publicationDate":"2016-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-01-01DOI: 10.14722/NDSS.2016.23108
A. Biryukov, D. Khovratovich
The proof-of-work is a central concept in modern cryptocurrencies, but the requirement for fast verification so far made it an easy prey for GPU-, ASIC-, and botnet-equipped users. The attempts to rely on memory-intensive computations in order to remedy the disparity between architectures have resulted in slow or broken schemes. In this paper we solve this open problem and show how to construct an asymmetric proof-of-work (PoW) based on a computationally hard problem, which requires a lot of memory to generate a proof (called ”memory-hardness” feature) but is instant to verify. Our primary proposal is a PoW based on the generalized birthday problem and enhanced Wagner’s algorithm for it. We introduce the new technique of algorithm binding to prevent cost amortization and demonstrate that possible parallel implementations are constrained by memory bandwidth. Our scheme has tunable and steep time-space tradeoffs, which impose large computational penalties if less memory is used. Our solution is practical and ready to deploy: a reference implementation of a proof-of-work requiring 700 MB of RAM runs in 30 seconds on a 1.8 GHz CPU, increases the computations by the factor of 1000 if memory is halved, and presents a proof of just 148 bytes long.
{"title":"Equihash: Asymmetric Proof-of-Work Based on the Generalized Birthday Problem","authors":"A. Biryukov, D. Khovratovich","doi":"10.14722/NDSS.2016.23108","DOIUrl":"https://doi.org/10.14722/NDSS.2016.23108","url":null,"abstract":"The proof-of-work is a central concept in modern cryptocurrencies, but the requirement for fast verification so far made it an easy prey for GPU-, ASIC-, and botnet-equipped users. The attempts to rely on memory-intensive computations in order to remedy the disparity between architectures have resulted in slow or broken schemes. In this paper we solve this open problem and show how to construct an asymmetric proof-of-work (PoW) based on a computationally hard problem, which requires a lot of memory to generate a proof (called ”memory-hardness” feature) but is instant to verify. Our primary proposal is a PoW based on the generalized birthday problem and enhanced Wagner’s algorithm for it. We introduce the new technique of algorithm binding to prevent cost amortization and demonstrate that possible parallel implementations are constrained by memory bandwidth. Our scheme has tunable and steep time-space tradeoffs, which impose large computational penalties if less memory is used. Our solution is practical and ready to deploy: a reference implementation of a proof-of-work requiring 700 MB of RAM runs in 30 seconds on a 1.8 GHz CPU, increases the computations by the factor of 1000 if memory is halved, and presents a proof of just 148 bytes long.","PeriodicalId":36240,"journal":{"name":"Ledger","volume":"2 1","pages":"1-30"},"PeriodicalIF":0.7,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.14722/NDSS.2016.23108","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67132614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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