Swiper and Dora: efficient solutions to weighted distributed problems

The majority of fault-tolerant distributed algorithms are designed assuming a nominal corruption model, in which at most a fraction $f_n$ of parties can be corrupted by the adversary. However, due to the infamous Sybil attack, nominal models are not sufficient to express the trust assumptions in open (i.e., permissionless) settings. Instead, permissionless systems typically operate in a weighted model, where each participant is associated with a weight and the adversary can corrupt a set of parties holding at most a fraction $f_w$ of total weight. In this paper, we suggest a simple way to transform a large class of protocols designed for the nominal model into the weighted model. To this end, we formalize and solve three novel optimization problems, which we collectively call the weight reduction problems, that allow us to map large real weights into small integer weights while preserving the properties necessary for the correctness of the protocols. In all cases, we manage to keep the sum of the integer weights to be at most linear in the number of parties, resulting in extremely efficient protocols for the weighted model. Moreover, we demonstrate that, on weight distributions that emerge in practice, the sum of the integer weights tends to be far from the theoretical worst-case and, often even smaller than the number of participants. While, for some protocols, our transformation requires an arbitrarily small reduction in resilience (i.e., $f_w = f_n - \epsilon$), surprisingly, for many important problems we manage to obtain weighted solutions with the same resilience ($f_w = f_n$) as nominal ones. Notable examples include asynchronous consensus, verifiable secret sharing, erasure-coded distributed storage and broadcast protocols

Asynchronous Reconfiguration with Byzantine Failures

Replicated services are inherently vulnerable to failures and security breaches. In a long-running system, it is, therefore, indispensable to maintain a reconfiguration mechanism that would replace faulty replicas with correct ones. An important challenge is to enable reconfiguration without affecting the availability and consistency of the replicated data: the clients should be able to get correct service even when the set of service replicas is being updated. In this paper, we address the problem of reconfiguration in the presence of Byzantine failures: faulty replicas or clients may arbitrarily deviate from their expected behavior. We describe a generic technique for building asynchronous and Byzantine fault-tolerant reconfigurable objects: clients can manipulate the object data and issue reconfiguration calls without reaching consensus on the current configuration. With the help of forward-secure digital signatures, our solution makes sure that superseded and possibly compromised configurations are harmless, that slow clients cannot be fooled into reading stale data, and that Byzantine clients cannot cause a denial of service by flooding the system with reconfiguration requests. Our approach is modular and based on dynamic lattice agreement abstraction, and we discuss how to extend it to enable Byzantine fault-tolerant implementations of a large class of reconfigurable replicated services

THE WAY TO INCREASE INFORMATION CAPACITY OF FINANCIAL STATEMENTS

The article suggests an approach designed to increase the effectiveness of financial statement analysis, as one of the main tools of corporate management. The authors define the disadvantages of existing methods and propose characteristics necessary for an effective decision supporting tool. The method of reference trends is shown to meet the preset requirements, which is proved by a supporting example

Трансформація функцій новинних телеграм-каналів під час війни

The article describes the transformational processes that occur in the functioning of public telegram channels during the full-scale Russian invasion. In the article the author suggests a classification of contemporary trends in the development of Telegram: as a service for exchanging instant messages for notifications, an additional platform for media, a cross-media channel, and an independent media platform. According to identified trend, it is determined the functional paradigm of different kinds of news Telegram channels that are registered in the section “News and Media” of professionals (corporate and personal) as well as amateur journalists, verified and anonymous. The article highlights the peculiarities of informational function implementation during the war period, in particular, the transformation of the standards in new journalism; it also characterizes the peculiarities of the communicative function, as well as the function of forming the agenda and generating the Internet traffic on other cross-media platforms on professional journalistic telegram channels (on the example of "UP. Line", “Radio Svoboda” and “Suspіlne Novini”). The prospects for winning public telegram channels from an independent media platform and the cross-media channel are stated. The peculiarities of the implementation of the functions to forming public opinion, social organization (stimulation of the social activity), and the public self-organization in personal journalistic and amateur new telegram channels during the period of the full-scale invasion. The input of amateur channels (“Lachen pyshe”, “Sternenko”, “Nikolaevsky Vanek”) is analyzed to change the functions of new resources in the messenger. The author pays attention to the deformation of the standards of new journalism in unverified anonymous telegram channels. The author compares informative, entertaining, psychotherapeutic functions of amateur new resources (based on the telegram channels "Truha Ukraina", "Ukraina Seychas", and "Ukraine Now").У статті розглянуто трансформаційні процеси, що спостерігаються у функціонуванні публічних телеграм-каналів під час повномасштабного російського вторгнення. Запропоновано класифікацію сучасних напрямів розвитку телеграму, як-то: сервіс обміну миттєвими повідомленнями, додаткова платформа медіадіяльності, канал кросмедіа та самостійна медіаплатформа. Відповідно до ідентифікованих напрямів визначено функції різних видів новинних телеграм-каналів, зареєстрованих у розділі «Новини і ЗМІ» професійних журналістських (корпоративних та персональних) й аматорських, верифікованих та анонімних. Акцентовано на особливостях реалізації інформаційної функції під час війни, зокрема трансформації стандартів новинної журналістики, схарактеризовано специфіку комунікативної функції, а також функцій формування порядку денного та генерації трафіку на інші платформи кросмедіа в професійних журналістських телеграм-каналах (на прикладі «УП. Стрічка», «Радіо Свобода» та «Суспільне Новини»). З’ясовано перспективи використання публічних телеграм-каналів як самостійної медіаплатформи та каналу кросмедіа. Розглянуто особливості реалізації функцій формування громадської думки, соціальної організації (стимуляції суспільної активності) й громадянської самоорганізації в персональних журналістських та аматорських новинних телеграм-каналах у період повномасштабного вторгнення. Проаналізовано вплив аматорських каналів («Лачен пише», «Sternenko», «Николаевский Ванек») на зміну функцій новинних ресурсів у месенджері. Звернено увагу на деформацію стандартів новинної журналістики в неверифікованих анонімних телеграм-каналах. Схарактеризовано співмірність інформаційної, розважальної та психотерапевтичної функцій аматорських новинних ресурсів (на прикладі телеграм-каналів «Труха Украина», «Украина Сейчас», «Ukraine Now»)

Permissionless and Asynchronous Asset Transfer

Most modern asset transfer systems use consensus to maintain a totally ordered chain of transactions. It was recently shown that consensus is not always necessary for implementing asset transfer. More efficient, asynchronous solutions can be built using reliable broadcast instead of consensus. This approach has been originally used in the closed (permissioned) setting. In this paper, we extend it to the open (permissionless) environment. We present {Pastro}, a permissionless and asynchronous asset-transfer implementation, in which quorum systems, traditionally used in reliable broadcast, are replaced with a weighted Proof-of-Stake mechanism. {Pastro} tolerates a dynamic adversary that is able to adaptively corrupt participants based on the assets owned by them

CryptoConcurrency: (Almost) Consensusless Asset Transfer with Shared Accounts

A typical blockchain protocol uses consensus to make sure that mutually mistrusting users agree on the order in which their operations on shared data are executed. It is known, however, that asset transfer systems, by far the most popular application of blockchains, can be implemented without consensus. Assuming that no account can be accessed concurrently, i.e., that every account belongs to a single owner, one can efficiently implement an asset transfer system in a purely asynchronous, consensus-free manner. It has been also shown that asset transfer with shared accounts is impossible to implement without consensus. In this paper, we propose CryptoConcurrency, an asset transfer protocol that allows concurrent accesses to be processed in parallel, without involving consensus, whenever possible. More precisely, if concurrent transfer operations on a given account do not lead to overspending, i.e., can all be applied without the account balance going below zero, they proceed in parallel. Otherwise, the account's owners may have to access an external consensus object. We allow each account to use its own consensus implementation, which only the owners of this account trust

Swiper and Dora: efficient solutions to weighted distributed problems

The majority of fault-tolerant distributed algorithms are designed assuming a nominal corruption model, in which at most a fraction $f_n$ of parties can be corrupted by the adversary. However, due to the infamous Sybil attack, nominal models are not sufficient to express the trust assumptions in open (i.e., permissionless) settings. Instead, permissionless systems typically operate in a weighted model, where each participant is associated with a weight and the adversary can corrupt a set of parties holding at most a fraction $f_w$ of total weight. In this paper, we suggest a simple way to transform a large class of protocols designed for the nominal model into the weighted model. To this end, we formalize and solve three novel optimization problems, which we collectively call the weight reduction problems, that allow us to map large real weights into small integer weights while preserving the properties necessary for the correctness of the protocols. In all cases, we manage to keep the sum of the integer weights to be at most linear in the number of parties, resulting in extremely efficient protocols for the weighted model. Moreover, we demonstrate that, on weight distributions that emerge in practice, the sum of the integer weights tends to be far from the theoretical worst-case and, often even smaller than the number of participants. While, for some protocols, our transformation requires an arbitrarily small reduction in resilience (i.e., $f_w = f_n - \epsilon$), surprisingly, for many important problems we manage to obtain weighted solutions with the same resilience ($f_w = f_n$) as nominal ones. Notable examples include asynchronous consensus, verifiable secret sharing, erasure-coded distributed storage and broadcast protocols. While there are ad-hoc weighted solutions to some of these problems, the protocols yielded by our transformations enjoy all the benefits of nominal solutions, including simplicity, efficiency, and a wider range of possible cryptographic assumptions

A new design proposal for composite beams with powder actuated shear connectors

This paper introduces a proposal for the SP 266.1325800 code update, which is applied as a national building code for composite structure design in Russian and some CIS countries. The proposal is based on deep codes analyze and comparison and previous authors’ publications. The research is dedicated to nailed shear connectors’ behavior in composite beams with profiled sheeting. The proposal provides a less conservative approach for composite beams with ductile shear connectors and takes into account additional conditions, such as decking geometry and the structure’s performance under fire. The proposed methodology defines the main geometric characteristics of the composite cross-section before determining the shear connector type. If ductile connectors are chosen, it is recommended to use partial design methods for shear connection definition due to the economic benefits of the proposal. The proposal is verified on powder-actuated shear connectors and should be double-checked with other working examples and connector types. The results show that the structure designed according to the new proposal is 13% less utilized with a smaller quantity of shear connectors (22% less) under the same load. It provides benefits from the structure costs and labor time