Foundations of Dynamic BFT

This paper studies dynamic BFT, where replicas can join and leave the system dynamically, a primitive that is nowadays increasingly needed. We provide a formal treatment for dynamic BFT protocols, endowing them with a flexible syntax and various security definitions. We demonstrate the challenges of extending static BFT to dynamic BFT. Then we design and implement Dyno, a highly efficient dynamic BFT protocol under the partial synchrony model. We show that Dyno can seamlessly handle membership changes without incurring performance degradation

Signature-Free Atomic Broadcast with Optimal O(n2)O(n^2) Messages and O(1)O(1) Expected Time

Byzantine atomic broadcast (ABC) is at the heart of permissioned blockchains and various multi-party computation protocols. We resolve a long-standing open problem in ABC, presenting the first information-theoretic (IT) and signature-free asynchronous ABC protocol that achieves optimal $O(n^2)$ messages and $O(1)$ expected time. Our ABC protocol adopts a new design, relying on a reduction from---perhaps surprisingly---a somewhat neglected primitive called multivalued Byzantine agreement (MBA)

Byzantine Reliable Broadcast with O(nL+kn+n2logn)O(nL+kn+n^2 log n) Communication

Byzantine reliable broadcast (BRB) is one of the most fundamental primitives in fault-tolerant distributed computing. It is well-known that the best BRB protocol one can hope for has $O(nL+n^2)$ communication. It is unclear if this bound is achievable. This paper provides a novel BRB protocol---BRB1, which achieves $O(nL + kn + n^2 log n)$ communication, where $n$, $L$, and $k$ are the number of replicas, the message length, and the security parameter, respectively. Our protocol is efficient, because the only building blocks we need are threshold signatures which have been used in various Byzantine fault-tolerant (BFT) protocols (e.g., SBFT, HoneyBadgerBFT, HotStuff). Our protocol is the first asynchronous BRB protocol that breaks the known $O(nL+kn^2)$ bound

PACE: Fully Parallelizable BFT from Reproposable Byzantine Agreement

The classic asynchronous Byzantine fault tolerance (BFT) framework of Ben-Or, Kemler, and Rabin (BKR) and its descendants rely on reliable broadcast (RBC) and asynchronous binary agreement (ABA). However, BKR does not allow all ABA instances to run in parallel, a well-known performance bottleneck. We propose PACE, a generic framework that removes the bottleneck, allowing fully parallelizable ABA instances. PACE is built on RBC and reproposable ABA (RABA). Different from the conventional ABA, RABA allows a replica to change its mind and vote twice. We show how to efficiently build RABA protocols from existing ABA protocols and a new ABA protocol that we introduce. We implement six new BFT protocols: three in the BKR framework, and three in the PACE framework. Via a deployment using 91 replicas on Amazon EC2 across five continents, we show that all PACE instantiations, in both failure-free and failure scenarios, significantly outperform their BKR counterparts, and prior BFT protocols such as BEAT and Dumbo, in terms of latency, throughput, latency vs. throughput, and scalability

La representación de la comunicación social a través de la noción de "armonía"

Desde las épocas más remotas, el concepto de "armonía" ocupa un lugar central y determinante en la cultura china. Pero no es un concepto extático sino todo lo contrario: un término siempre en construcción al que a lo largo de la historia de la civilización china se le han agregado numerosos elementos. En un momento determinado, por presiones políticas se "realza exclusivamente el Confucianismo suprimiendo otras corrientes ideológicas"1. Este cambio se realizó en la era del emperador Wu de la dinastía Han (147-87), en donde la noción de 'armonía', que representa la arteria la dicha ideología, alcanzó una prosperidad sin precedentes. Desde ese momento, y a lo largo de dos mil años, la "armonía" se convirtió en el eje en la vida cotidiana, la sociedad y la cultura de China hasta el momento actual. A continuación, vamos a aclarar este concepto del que tenemos en cuenta su extraordinaria complejidad y riqueza de significados, explicándolo en cinco partes: el estudio del propio término "armonía", su inclusión en la tradición religiosa china, las formas de representación que adopta en la cultura oriental, su inserción y su presencia en la vida cotidiana y una reflexión acerca de la actual "Sociedad Armoniosa"

Antidiabetic effect of Tibetan medicine Tang-Kang-Fu-San in db/db mice via activation of PI3K/Akt and AMPK pathways

This study was to investigate the anti-diabetic effects and molecular mechanisms of Tang-Kang-Fu-San (TKFS), a traditional Tibetan medicine, in treating type 2 diabetes mellitus of spontaneous diabetic db/db mice. Firstly HPLC fingerprint analysis was performed to gain the features of the chemical compositions of TKFS. Next different doses of TKFS (0.5 g/kg, 1.0 g/kg, and 2.0 g/kg) were administrated via oral gavage to db/db mice and their controls for 4 weeks. TKFS significantly lowered hyperglycemia and ameliorated insulin resistance (IR) in db/db mice, indicated by results from multiple tests, including fasting blood glucose test, intraperitoneal insulin and glucose tolerance tests, fasting serum insulin levels and homeostasis model assessment of IR analysis as well as histology of pancreas islets. TKFS also decreased concentrations of serum triglyceride, total and low-density lipoprotein cholesterol, even though it did not change the mouse body weights. Results from western blot and immunohistochemistry analysis indicated that TKFS reversed the down-regulation of p-Akt and p-AMPK, and increased the translocation of Glucose transporter type 4 in skeletal muscles of db/db mice. In all, TKFS had promising benefits in maintaining the glucose homeostasis and reducing IR. The underlying molecular mechanisms are related to promote Akt and AMPK activation and Glucose transporter type 4 translocation in skeletal muscles. Our work showed that multicomponent Tibetan medicine TKFS acted synergistically on multiple molecular targets and signaling pathways to treat type 2 diabetes mellitus

ByzID: Byzantine Fault Tolerance from Intrusion Detection

Building robust network services that can withstand a wide range of failure types is a fundamental problem in distributed systems. The most general approach, called Byzantine fault tolerance, can mask arbitrary failures. Yet it is often considered too costly to deploy in practice, and many solutions are not resilient to performance attacks. To address this concern we leverage two key technologies already widely deployed in cloud computing infrastructures: replicated state machines and intrusiondetection systems.First, we have designed a general framework for constructing Byzantine failure detectors based on an intrusion detection system. Based on such a failure detector, we have designed and built a practical Byzantine fault-tolerant protocol, which has costs comparable to crash-resilient protocols like Paxos. More importantly, our protocol is particularly robust against several key attacks such as flooding attacks, timing attacks, and fairness attacks, that are typically not handled well by Byzantine fault masking procedures

BG: A Modular Treatment of BFT Consensus

We provide an expressive framework that allows analyzing and generating provably secure, state-of-the-art Byzantine fault-tolerant (BFT) protocols. Our framework is hierarchical, including three layers. The top layer is used to model the message pattern and abstract key functions on which BFT algorithms can be built. The intermediate layer provides the core functions with high-level properties sufficient to prove the security of the top-layer algorithms. The bottom layer carefully defines predicates according to which we offer operational realizations for the core functions. All three layers in our framework are extensible and enable innovation. One may modify or extend any layer to theoretically cover all BFT protocols, known and unknown. Indeed, unlike prior BFT frameworks, our framework can analyze and recast BFT protocols in an exceedingly fine-grained manner. More importantly, our framework can readily generate new BFT protocols by simply enumerating the parameters in the framework. In this paper, we show that the framework allows us to fully specify and formally prove the security for 23 BFT protocols, including protocols matching HotStuff, Fast-HotStuff, Jolteon, and Marlin, and among these protocols, seven new protocols outperforming existing ones or achieving meaningful trade-offs among various performance metrics

FIN: Practical Signature-Free Asynchronous Common Subset in Constant Time

Asynchronous common subset (ACS) is a powerful paradigm enabling applications such as Byzantine fault-tolerance (BFT) and multi-party computation (MPC). The most efficient ACS framework in the information-theoretic setting is due to Ben-Or, Kelmer, and Rabin (BKR, 1994). The BKR ACS protocol has been both theoretically and practically impactful. However, the BKR protocol has an $O(\log n)$ running time (where $n$ is the number of replicas) due to the usage of $n$ parallel asynchronous binary agreement (ABA) instances, impacting both performance and scalability. Indeed, for a network of 16~64 replicas, the parallel ABA phase occupies about 95%~97% of the total runtime in BKR. A long-standing open problem is whether we can build an ACS framework with $O(1)$ time while not increasing the message or communication complexity of the BKR protocol. In this paper, we resolve the open problem, presenting the first constant-time ACS protocol with $O(n^3)$ messages in the information-theoretic and signature-free settings. Moreover, as a key ingredient of our new ACS framework and an interesting primitive in its own right, we provide the first information-theoretic multivalued validated Byzantine agreement (MVBA) protocol with $O(1)$ time and $O(n^3)$ messages. Both results can improve---asymptotically and concretely---various applications using ACS and MVBA in the information-theoretic, quantum-safe, or signature-free settings. As an example, we implement FIN, a BFT protocol instantiated using our framework. Via a 121-server deployment on Amazon EC2, we show FIN is significantly more efficient than PACE (CCS 2022), the state-of-the-art asynchronous BFT protocol of the same type. In particular, FIN reduces the overhead of the ABA phase to as low as 1.23% of the total runtime, and FIN achieves up to 3.41x the throughput of PACE. We also show that FIN outperforms other BFT protocols with the standard liveness property such as Dumbo and Speeding Dumbo