Jonathan Katz, A. Kiayias, Hong-Sheng Zhou, Vassilis Zikas
Universally composable (UC) protocols retain their security properties even when run concurrently alongside arbitrary other protocols. Unfortunately, it is known that UC multiparty computation (for general functionalities, and without assuming honest majority) is impossible without some form of setup. To circumvent this impossibility, various complete setup assumptions have been proposed. With only a few exceptions, past work has viewed these setup assumptions as being implemented by some ideal, incorruptible entity. Any such entity is thus a single point of failure, and security fails catastrophically in case the setup entity is subverted by an adversary. We propose here a clean, general, and generic approach for distributing trust among m arbitrary setups, by modeling potential corruption of setups within the UC framework, where such corruption might be fail-stop, passive, or arbitrary and is in addition to possible corruption of the parties themselves. We show several feasibility and impossibility results in this model, for different specifications of the corruptible sets. For example, we show that given m complete setups, up to t of which might be actively corrupted in an adaptive manner, general multiparty computation with no honest majority is possible if and only if t < m/2.
{"title":"Distributing the setup in universally composable multi-party computation","authors":"Jonathan Katz, A. Kiayias, Hong-Sheng Zhou, Vassilis Zikas","doi":"10.1145/2611462.2611480","DOIUrl":"https://doi.org/10.1145/2611462.2611480","url":null,"abstract":"Universally composable (UC) protocols retain their security properties even when run concurrently alongside arbitrary other protocols. Unfortunately, it is known that UC multiparty computation (for general functionalities, and without assuming honest majority) is impossible without some form of setup. To circumvent this impossibility, various complete setup assumptions have been proposed. With only a few exceptions, past work has viewed these setup assumptions as being implemented by some ideal, incorruptible entity. Any such entity is thus a single point of failure, and security fails catastrophically in case the setup entity is subverted by an adversary. We propose here a clean, general, and generic approach for distributing trust among m arbitrary setups, by modeling potential corruption of setups within the UC framework, where such corruption might be fail-stop, passive, or arbitrary and is in addition to possible corruption of the parties themselves. We show several feasibility and impossibility results in this model, for different specifications of the corruptible sets. For example, we show that given m complete setups, up to t of which might be actively corrupted in an adaptive manner, general multiparty computation with no honest majority is possible if and only if t < m/2.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127860553","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 new round-based asynchronous consensus algorithm that copes with up to t < n/3 Byzantine processes, where n is the total number of processes. In addition of not using signature, not assuming a computationally-limited adversary, while being optimal with respect to the value of t, this algorithm has several noteworthy properties: the expected number of rounds to decide is four, each round is composed of two or three communication steps and involves O(n2) messages, and a message is composed of a round number plus a single bit. To attain this goal, the consensus algorithm relies on a common coin as defined by Rabin, and a new extremely simple and powerful broadcast abstraction suited to binary values. The main target when designing this algorithm was to obtain a cheap and simple algorithm. This was motivated by the fact that, among the first-class properties, simplicity --albeit sometimes under-estimated or even ignored-- is a major one.
{"title":"Signature-free asynchronous byzantine consensus with t < n/3 and o(n2) messages","authors":"A. Mostéfaoui, Moumen Hamouma, M. Raynal","doi":"10.1145/2611462.2611468","DOIUrl":"https://doi.org/10.1145/2611462.2611468","url":null,"abstract":"This paper presents a new round-based asynchronous consensus algorithm that copes with up to t < n/3 Byzantine processes, where n is the total number of processes. In addition of not using signature, not assuming a computationally-limited adversary, while being optimal with respect to the value of t, this algorithm has several noteworthy properties: the expected number of rounds to decide is four, each round is composed of two or three communication steps and involves O(n2) messages, and a message is composed of a round number plus a single bit. To attain this goal, the consensus algorithm relies on a common coin as defined by Rabin, and a new extremely simple and powerful broadcast abstraction suited to binary values. The main target when designing this algorithm was to obtain a cheap and simple algorithm. This was motivated by the fact that, among the first-class properties, simplicity --albeit sometimes under-estimated or even ignored-- is a major one.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"1 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131450906","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}
{"title":"Session details: Session 7","authors":"P. Fatourou","doi":"10.1145/3246721","DOIUrl":"https://doi.org/10.1145/3246721","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130316829","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}
Dan Alistarh, O. Denysyuk, L. Rodrigues, N. Shavit
We consider the following natural problem: n failure-prone servers, communicating synchronously through message passing, must assign themselves one-to-one to n distinct items. Existing literature suggests two possible approaches to this problem. First, model it as an instance of tight renaming in synchronous message-passing systems; for deterministic solutions, a tight bound of Θ(log n) communication rounds is known. Second, model the scenario as an instance of randomized load-balancing, for which elegant sub-logarithmic solutions exist. However, careful examination reveals that known load-balancing schemes do not apply to our scenario, because they either do not tolerate faults or do not ensure one-to-one allocation. It is thus natural to ask if sub-logarithmic solutions exist for this apparently simple but intriguing problem. In this paper, we combine the two approaches to provide a new randomized solution for tight renaming, which terminates in O(log log n) communication rounds with high probability, against a strong adaptive adversary. Our solution, called Balls-into-Leaves, combines the deterministic approach with a new randomized scheme to obtain perfectly balanced allocations. The algorithm arranges the items as leaves of a tree, and participants repeatedly perform random choices among the leaves. The algorithm exchanges information in each round to split the participants into progressively smaller groups whose random choices do not conflict. We then extend the algorithm to terminate early in O(log log f) rounds w.h.p., where f is the actual number of failures. These results imply an exponential separation between deterministic and randomized algorithms for the tight renaming problem in message-passing systems.
{"title":"Balls-into-leaves: sub-logarithmic renaming in synchronous message-passing systems","authors":"Dan Alistarh, O. Denysyuk, L. Rodrigues, N. Shavit","doi":"10.1145/2611462.2611499","DOIUrl":"https://doi.org/10.1145/2611462.2611499","url":null,"abstract":"We consider the following natural problem: n failure-prone servers, communicating synchronously through message passing, must assign themselves one-to-one to n distinct items. Existing literature suggests two possible approaches to this problem. First, model it as an instance of tight renaming in synchronous message-passing systems; for deterministic solutions, a tight bound of Θ(log n) communication rounds is known. Second, model the scenario as an instance of randomized load-balancing, for which elegant sub-logarithmic solutions exist. However, careful examination reveals that known load-balancing schemes do not apply to our scenario, because they either do not tolerate faults or do not ensure one-to-one allocation. It is thus natural to ask if sub-logarithmic solutions exist for this apparently simple but intriguing problem. In this paper, we combine the two approaches to provide a new randomized solution for tight renaming, which terminates in O(log log n) communication rounds with high probability, against a strong adaptive adversary. Our solution, called Balls-into-Leaves, combines the deterministic approach with a new randomized scheme to obtain perfectly balanced allocations. The algorithm arranges the items as leaves of a tree, and participants repeatedly perform random choices among the leaves. The algorithm exchanges information in each round to split the participants into progressively smaller groups whose random choices do not conflict. We then extend the algorithm to terminate early in O(log log f) rounds w.h.p., where f is the actual number of failures. These results imply an exponential separation between deterministic and randomized algorithms for the tight renaming problem in message-passing systems.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130453533","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}
J. Garay, Clint Givens, R. Ostrovsky, Pavel Raykov
In this paper we focus on sender-anonymous channels (a.k.a. Dining Cryptographers networks) and present a construction requiring a very low (constant) number of rounds of interaction while tolerating actively malicious behavior by some of the participants (up to less than half of them). Our construction is unconditionally secure (meaning that no bounds are placed on the computational power of the adversary), makes black-box use of a verifiable secret sharing (VSS) protocol, and is based on a special-purpose secure multiparty computation protocol implementing the method of "throwing darts;" its round complexity is essentially equal to that of the VSS protocol. In addition, since broadcast cannot be simulated in a point-to-point network when a third or more of the participants are corrupt, it is impossible to construct VSS (and, more generally, any other basic multiparty protocol) in this setting without using a "physical broadcast channel," and a recent line of research has sought to minimize the use of this expensive resource. Our anonymous channel protocol's reduction to VSS is broadcast-round-preserving, thus making the fewest (known to date) calls to the broadcast channel while running in an overall constant number of rounds. Finally, anonymous channels play an important role in the setup phase of an authentication technique known as pseudosignatures, which then may be used to simulate authenticated Byzantine agreement protocols in the information-theoretic setting. Plugging in our anonymous channel translates into a fast (and broadcast-efficient) pseudosignature construction.
{"title":"Fast and unconditionally secure anonymous channel","authors":"J. Garay, Clint Givens, R. Ostrovsky, Pavel Raykov","doi":"10.1145/2611462.2611494","DOIUrl":"https://doi.org/10.1145/2611462.2611494","url":null,"abstract":"In this paper we focus on sender-anonymous channels (a.k.a. Dining Cryptographers networks) and present a construction requiring a very low (constant) number of rounds of interaction while tolerating actively malicious behavior by some of the participants (up to less than half of them). Our construction is unconditionally secure (meaning that no bounds are placed on the computational power of the adversary), makes black-box use of a verifiable secret sharing (VSS) protocol, and is based on a special-purpose secure multiparty computation protocol implementing the method of \"throwing darts;\" its round complexity is essentially equal to that of the VSS protocol. In addition, since broadcast cannot be simulated in a point-to-point network when a third or more of the participants are corrupt, it is impossible to construct VSS (and, more generally, any other basic multiparty protocol) in this setting without using a \"physical broadcast channel,\" and a recent line of research has sought to minimize the use of this expensive resource. Our anonymous channel protocol's reduction to VSS is broadcast-round-preserving, thus making the fewest (known to date) calls to the broadcast channel while running in an overall constant number of rounds. Finally, anonymous channels play an important role in the setup phase of an authentication technique known as pseudosignatures, which then may be used to simulate authenticated Byzantine agreement protocols in the information-theoretic setting. Plugging in our anonymous channel translates into a fast (and broadcast-efficient) pseudosignature construction.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"2200 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130132282","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}
Threshold cryptography is a fundamental distributed computational paradigm for enhancing the availability and the security of cryptographic public-key schemes. It does it by dividing private keys into n shares handed out to distinct servers. In threshold signature schemes, a set of at least t+1 ≤ n servers is needed to produce a valid digital signature. Availability is assured by the fact that any subset of t+1 servers can produce a signature when authorized. At the same time, the scheme should remain robust (in the fault tolerance sense) and unforgeable (cryptographically) against up to t corrupted servers; i.e., it adds quorum control to traditional cryptographic services and introduces redundancy. Originally, most practical threshold signatures have a number of demerits: They have been analyzed in a static corruption model (where the set of corrupted servers is fixed at the very beginning of the attack), they require interaction, they assume a trusted dealer in the key generation phase (so that the system is not fully distributed), or they suffer from certain overheads in terms of storage (large share sizes). In this paper, we construct practical fully distributed (the private key is born distributed), non-interactive schemes --- where the servers can compute their partial signatures without communication with other servers--- with adaptive security (i.e., the adversary corrupts servers dynamically based on its full view of the history of the system). Our schemes are very efficient in terms of computation, communication, and scalable storage (with private key shares of size O(1), where certain solutions incur O(n) storage costs at each server). Unlike other adaptively secure schemes, our schemes are erasure-free (reliable erasure is a hard to assure and hard to administer property in actual systems). To the best of our knowledge, such a fully distributed highly constrained scheme has been an open problem in the area. In particular, and of special interest, is the fact that Pedersen's traditional distributed key generation (DKG) protocol can be safely employed in the initial key generation phase when the system is born -- although it is well-known not to ensure uniformly distributed public keys. An advantage of this is that this protocol only takes one round optimistically (in the absence of faulty player).
{"title":"Born and raised distributively: fully distributed non-interactive adaptively-secure threshold signatures with short shares","authors":"Benoît Libert, M. Joye, M. Yung","doi":"10.1145/2611462.2611498","DOIUrl":"https://doi.org/10.1145/2611462.2611498","url":null,"abstract":"Threshold cryptography is a fundamental distributed computational paradigm for enhancing the availability and the security of cryptographic public-key schemes. It does it by dividing private keys into n shares handed out to distinct servers. In threshold signature schemes, a set of at least t+1 ≤ n servers is needed to produce a valid digital signature. Availability is assured by the fact that any subset of t+1 servers can produce a signature when authorized. At the same time, the scheme should remain robust (in the fault tolerance sense) and unforgeable (cryptographically) against up to t corrupted servers; i.e., it adds quorum control to traditional cryptographic services and introduces redundancy. Originally, most practical threshold signatures have a number of demerits: They have been analyzed in a static corruption model (where the set of corrupted servers is fixed at the very beginning of the attack), they require interaction, they assume a trusted dealer in the key generation phase (so that the system is not fully distributed), or they suffer from certain overheads in terms of storage (large share sizes). In this paper, we construct practical fully distributed (the private key is born distributed), non-interactive schemes --- where the servers can compute their partial signatures without communication with other servers--- with adaptive security (i.e., the adversary corrupts servers dynamically based on its full view of the history of the system). Our schemes are very efficient in terms of computation, communication, and scalable storage (with private key shares of size O(1), where certain solutions incur O(n) storage costs at each server). Unlike other adaptively secure schemes, our schemes are erasure-free (reliable erasure is a hard to assure and hard to administer property in actual systems). To the best of our knowledge, such a fully distributed highly constrained scheme has been an open problem in the area. In particular, and of special interest, is the fact that Pedersen's traditional distributed key generation (DKG) protocol can be safely employed in the initial key generation phase when the system is born -- although it is well-known not to ensure uniformly distributed public keys. An advantage of this is that this protocol only takes one round optimistically (in the absence of faulty player).","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121809960","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}
Read copy update (RCU) is a novel synchronization mechanism, in which the burden of synchronization falls completely on the updaters, by having them wait for all pre-existing readers to finish their read-side critical section. This paper presents citrus, a concurrent binary search tree (BST) with a wait-free Contains operation, using RCU synchronization and fine-grained locking for synchronization among updaters. This is the first RCU-based data structure that allows concurrent updaters. While there are methodologies for using RCU to coordinate between readers and updaters, they do not address the issue of coordination among updaters, and indeed, all existing RCU-based data structures rely on coarse-grained synchronization between updaters. Experimental evaluation shows that citrus beats previous RCU-based search trees, even under mild update contention, and compares well with the best-known concurrent dictionaries.
{"title":"Concurrent updates with RCU: search tree as an example","authors":"M. Arbel, H. Attiya","doi":"10.1145/2611462.2611471","DOIUrl":"https://doi.org/10.1145/2611462.2611471","url":null,"abstract":"Read copy update (RCU) is a novel synchronization mechanism, in which the burden of synchronization falls completely on the updaters, by having them wait for all pre-existing readers to finish their read-side critical section. This paper presents citrus, a concurrent binary search tree (BST) with a wait-free Contains operation, using RCU synchronization and fine-grained locking for synchronization among updaters. This is the first RCU-based data structure that allows concurrent updaters. While there are methodologies for using RCU to coordinate between readers and updaters, they do not address the issue of coordination among updaters, and indeed, all existing RCU-based data structures rely on coarse-grained synchronization between updaters. Experimental evaluation shows that citrus beats previous RCU-based search trees, even under mild update contention, and compares well with the best-known concurrent dictionaries.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125621381","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 hardware transactional memory (HTM) becoming available in mainstream processors, lock-based critical sections may now initiate a hardware transaction instead of taking the lock, enabling their concurrent execution unless a real data conflict occurs. However, just a few transactional aborts can cause the lock to be acquired non-transactionally resulting in the serialization of all the threads, severely degrading the amount of speedup obtained. In this paper we provide two software extension mechanisms that considerably improve the concurrency and speedup levels attained by lock based programs using HTM-based lock elision. The first sacrifices opacity to achieve higher levels of concurrency, and the second retains opacity while reaching slightly lower levels of concurrency. Evaluation on STAMP and on data structure benchmarks on an Intel Haswell processor shows that these techniques improve the speedup by up to 3.5 times and $10$ times respectively, compared to using Haswell's hardware lock elision as is.
{"title":"Software-improved hardware lock elision","authors":"Y. Afek, A. Levy, Adam Morrison","doi":"10.1145/2611462.2611482","DOIUrl":"https://doi.org/10.1145/2611462.2611482","url":null,"abstract":"With hardware transactional memory (HTM) becoming available in mainstream processors, lock-based critical sections may now initiate a hardware transaction instead of taking the lock, enabling their concurrent execution unless a real data conflict occurs. However, just a few transactional aborts can cause the lock to be acquired non-transactionally resulting in the serialization of all the threads, severely degrading the amount of speedup obtained. In this paper we provide two software extension mechanisms that considerably improve the concurrency and speedup levels attained by lock based programs using HTM-based lock elision. The first sacrifices opacity to achieve higher levels of concurrency, and the second retains opacity while reaching slightly lower levels of concurrency. Evaluation on STAMP and on data structure benchmarks on an Intel Haswell processor shows that these techniques improve the speedup by up to 3.5 times and $10$ times respectively, compared to using Haswell's hardware lock elision as is.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115208898","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}
{"title":"Session details: Session 5","authors":"M. Yung","doi":"10.1145/3246719","DOIUrl":"https://doi.org/10.1145/3246719","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126588632","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}
Manfred Schwarz, Kyrill Winkler, U. Schmid, M. Biely, Peter Robinson
We present a k-set agreement algorithm for synchronous dynamic distributed systems with unidirectional links controlled by an omniscient adversary. Our algorithm automatically adapts to the actual network properties: If the network is sufficiently well-connected, it solves consensus, while degrading gracefully to general k-set agreement in less well-behaved runs. The algorithm is oblivious to the maximum number of system-wide decision values k, which is bounded by the number of certain strongly connected components occurring in the dynamically changing network in a run. Related impossibility results reveal that this bound is close to the solvability border for k-set agreement. To the best of our knowledge, this is the first consensus algorithm that degrades in a graceful way in a dynamic network.
{"title":"Brief announcement: gracefully degrading consensus and k-set agreement under dynamic link failures","authors":"Manfred Schwarz, Kyrill Winkler, U. Schmid, M. Biely, Peter Robinson","doi":"10.1145/2611462.2611506","DOIUrl":"https://doi.org/10.1145/2611462.2611506","url":null,"abstract":"We present a k-set agreement algorithm for synchronous dynamic distributed systems with unidirectional links controlled by an omniscient adversary. Our algorithm automatically adapts to the actual network properties: If the network is sufficiently well-connected, it solves consensus, while degrading gracefully to general k-set agreement in less well-behaved runs. The algorithm is oblivious to the maximum number of system-wide decision values k, which is bounded by the number of certain strongly connected components occurring in the dynamically changing network in a run. Related impossibility results reveal that this bound is close to the solvability border for k-set agreement. To the best of our knowledge, this is the first consensus algorithm that degrades in a graceful way in a dynamic network.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127347165","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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