Wai Yan Maung Maung Thin, Naipeng Dong, Guangdong Bai, Jin Dong
Blockchain technology relies on consensus algorithms to resolve conflicts in Byzantine environments. New blockchain algorithms are rapidly designed and implemented without a properly conducted formal analysis and verification. In this paper, we conducted a study on Tendermint which is a proof-of-stake consensus algorithm. We verified that the consensus protocol is deadlock-free and is able to reach consensus when at least 2/3 of the network is in agreement. We also proved that a minority set of nodes that compose more than 1/3 of the network is enough to censor the majority of the network and prevent the network from reaching consensus and conclude that the algorithm has some shortcomings on availability.
This paper presents a stochastic model for block arrival times based on the difficulty retargeting rule used in Bitcoin, as well as other proof-of-work blockchains. Unlike some previous work, this paper explicitly models the difficulty target as a random variable which is a function of the previous block arrival times and affecting the block times in the next retargeting period. An explicit marginal distribution is derived for the time between successive blocks (the blocktime), while allowing for randomly changing difficulty. This paper also aims to serve as an introduction to Bitcoin and proof-of-work blockchains for the controls community, focusing on the difficulty retargeting procedure used in Bitcoin.
Abstract: This contribution examines the formation of (blockchain-based) smart contracts. The term smart contract is used to refer to software programmes which are often, but not necessarily, built on blockchain technology as a set of promises, specified in digital form, including protocols within which the parties perform on these promises. It is regularly said that smart contracts are neither legal contracts in the traditional sense nor they are smart and that the term is therefore a misnomer. The crucial question this article is trying to answer is whether the traditional common law concept of contract formation is seriously challenged by the rise of smart contracts. As such, are smart contracts marking the end of contract formation as we know it or is it just much ado about nothing? Résumé: Cette contribution examine la formation de contrats intelligents (basés sur la blockchain). Le terme de contrat intelligent est utilisé pour faire référence aux programmes de software qui sont souvent, mais pas nécessairement, conçus sur la technologie de la blockchain comme un ensemble de promesses, spécifiées sous forme digitale, comprenant des protocoles au sein desquels les parties accomplissent ces promesses.On a souvent dit que les contrats intelligents ne sont ni des contrats juridiques au sens traditionnel ni intelligents et que le terme est donc inapproprié. La question cruciale à laquelle le présent article tente de répondre est de savoir si le concept traditionnel dans la common law de la formation du contrat est sérieusement mis au défi par l’arrivée des contrats intelligents. Comme tels, les contrats intelligents marquent-ils la fin de la formation des contrats telle que nous la connaissons ou ne s’agit-il finalement que de ‘beaucoup de bruit pour rien’?
Abstract: This article investigates the legal dimension of smart contracts. In particular, it reviews their existing definitions in some of the main laws enacted and scholarly articles published to date, proposes its own version, to then move on to consider to what extent new legal categories are warranted to deal with this apparently totally new way of making legally binding agreements. It concludes by providing some final remarks with regard to relevant legal categories and attempts to advance a number of solutions to the legal questions raised by the application of smart contracts. Résume: Le présent article étudie la dimension juridique de contrats intelligents. En particulier, il passe en revue leurs définitions qui se trouvent dans certaines des lois essentielles promulguées et dans des articles académiques publiés jusqu’à présent, il propose sa version propre, et considère ensuite dans quelle mesure de nouvelles catégories juridiques sont justifiées pour traiter cette manière apparemment tout à fait nouvelle de passer des accords juridiquement obligatoires. Il conclut par quelques remarques finales concernant des catégories juridiques importantes et tente d’apporter certaines solutions aux questions juridiques soulevées par l’application de contrats intelligents.
Xu Wang, Xuan F. Zha, Guangsheng Yu, Wei Ni · 8 authors
Ethereum, as the first Turing-complete blockchain platform, provides various application program interfaces for developers. Although blockchain has highly improved security, faulty configuration and usage can result in serious vulnerabilities. In this paper, we focus on the security vulnerabilities of the official Go-version Ethereum client (geth). The vulnerabilities are because of the insecure API design and the specific Ethereum wallet mechanism. We demonstrate attacks exploiting these vulnerabilities in an Ethereum testbed. The vulnerabilities are confirmed by the scanning results on the public Internet. Finally, corresponding countermeasures against attacks are provided to enhance the security of the Ethereum platform.
Today's commercial model for edge computing services consists in lightweight devices at the network edge connected through the Internet to remote cloud data centers. Microclouds are an alternative vision of edge computing, where the cloud infrastructure runs at the network edge leveraging decentralized resource contributions of a community. But current attempts to build such microclouds lack a collaborative governance system to operate successfully. In this paper we discuss the opportunity to implement with blockchain technologies key services to enable the decentralized collaborative governance of microclouds. A multiagent approach could further contribute to improve the efficiency in the decision making in the collaborative governance service.
The fundamental problem in digital record-keeping is establishing consensus on an update to a ledger, e.g., a payment. Consensus must be achieved in the presence of faults-situations in which some computers are offline or fail to function appropriately. Traditional centralized record-keeping systems rely on trust in a single entity to achieve consensus. Blockchains decentralize record-keeping, dispensing with the need for trust in a single entity, but some instead build a consensus based on the wasteful expenditure of computational resources (proof-of-work). An ideal method of consensus would be tolerant to faults, avoid the waste of computational resources, and be capable of implementing all individually rational transfers of value among agents. We prove a Blockchain Trilemma: any method of consensus, be it centralized or decentralized, must give up (i) fault-tolerance, (ii) resource-efficiency, or (iii) full transferability.
Georgia Avarikioti, Felix Laufenberg, Jakub Sliwinski, Yuyi Wang · 5 authors
Micropayment channels are the most prominent solution to the limitation on transaction throughput in current blockchain systems. However, in practice channels are risky because participants have to be online constantly to avoid fraud, and inefficient because participants have to open multiple channels and lock funds in them. To address the security issue, we propose a novel mechanism that involves watchtowers incentivized to watch the channels and reveal a fraud. Our protocol does not require participants to be online constantly watching the blockchain. The protocol is secure, incentive compatible and lightweight in communication. Furthermore, we present an adaptation of our protocol implementable on the Lightning protocol. Towards efficiency, we examine specific topological structures in the blockchain transaction graph and generalize the construction of channels to enable topologies better suited to specific real-world needs. In these cases, our construction reduces the required amount of signatures for a transaction and the total amount of locked funds in the system.
Many blockchain consensus protocols have been proposed recently to scale the throughput of a blockchain with available bandwidth. However, these protocols are becoming increasingly complex, making it more and more difficult to produce proofs of their security guarantees. We propose a novel permissionless blockchain protocol OHIE which explicitly aims for simplicity. OHIE composes as many parallel instances of Bitcoin's original (and simple) backbone protocol as needed to achieve excellent throughput. We formally prove the safety and liveness properties of OHIE. We demonstrate its performance with a prototype implementation and large-scale experiments with up to 50,000 nodes. In our experiments, OHIE achieves linear scaling with available bandwidth, providing about 4-10 Mbps transaction throughput (under 8-20 Mbps per-node available bandwidth configurations) and at least about 20x better decentralization over prior works.
The purpose of the study is to investigate a financial component of interbudget relations in Ukraine in part of providing and improving the horizontal equalization of regional budgets under the conditions of decentralization. We aim to measure horizontal fiscal imbalance in Ukraine before and after implementation of the decentralization reform: the changes in the horizontal levelling of regional budgets in pre-reform period and during a period of budgetary decentralization. The methodology of the research is based on the theory of public finance, in particular on the theory of fiscal federalism. Study uses the estimation of the statistical data of the authorized bodies related to the distribution of the state budget funds over the regions of Ukraine. The time interval of the research is four years (2015-2018) due to the starting time of implementation of the decentralization reform in Ukraine and the availability of published statistical information. Software packages MS Excel 2016 and SSPSS Statistics 17.0, StatGraphics Plus 5.0 are used for economic-statistical calculations. Such analysis is conducted using the methods of synthesis, tabular, graphic, cluster and correlation analysis. The constrains of the study are related to the incomplete statistical data of the State Statistics Service of Ukraine, the State Treasury Service of Ukraine and the Ministry of Finance of Ukraine. Results. It is proved that the equalization subsidy was the main tool for equalizing of the revenue part of local budgets. It formed about a quarter of revenue of local budgets and about half of official transfers of local budgets. It is found out that horizontal imbalance is much lower after the decentralization reform in Ukraine: after reforming the horizontal equalization, the absolute volume of the horizontal equalization decreased by 11.5 times, relative indicators decreased by 15 times. A detailed analysis reveals the existence of imbalances in the horizontal equalization of regional budgets in Ukraine in 2015-2018. Furthermore, the present system of horizontal equalization is ineffective according to the criterion of fiscal efficiency and contradicts a basic approach of budget decentralization. Four budget clusters are identified based on the criterion of distribution of basic subsidy: 1-st cluster of budgets with average size of basic subsidy (budgets of Vinnytsia, Zhytomyr, Chernigiv, Kirovograd, Khmelnytsky, Mykolayiv and Cherkasy regions); 2-nd cluster of budgets with minimum amounts of basic subsidy (budgets of Luhansk and Sumy regions), and with the change of directions of horizontal equalizationts (budgets of Donetsk, Kharkiv, Odesa and Lviv regions); 3-rd cluster of budgets with maximum size of the basic subsidy (regional budgets of Volyn, Rivne, Kherson, Ivano-Frankivsk, Ternopil, Zakarpattia and Chernivtsi regions); 4-th cluster of budgets of those who transfered a reverse grant to the State Budget of Ukraine (budgets of Dnipropetrovsk, Zaporizhzhia, Kyiv and Poltava regions). Practical meaning. The directions of improvement of the horizontal equalization of regional budgets in Ukraine are substantiated, among them: introduction of the index of horizontal equalization; constance of approaches to horizontal equalization for three years according to requirements of medium-term budget planning and sustainable development of regions; extending the interval of the index of horizontal levelling. The prospects for further study are related to the justification of the mechanism of financial provision of local government in the context of implementation policy of decentralization.
У статті охарактеризовано основні виклики, що постали перед фінансовими системами країн світу з огляду на появу криптовалют, які здатні порушити монополію центральних банків щодо контролю грошової маси в обігу. Визначено наявні у світовій та вітчизняній практиці підходи до визначення сутності криптовалют. Розглянуто основні відмінності між електронними грошима і віртуальною валютою. Здійснено оцінку тенденцій на ринку криптовалют, динаміки капіталізації основних криптовалют, зокрема біткоіна, структури криптовалютного ринку. Проаналізовано ситуацію відносно визначення правового статусу криптовалюти в зарубіжних країнах та Україні, обґрунтовано наявність у світовій практиці п’яти основних підходів до регулювання ринку криптовалют. Визначено переваги та недоліки потенційного використання криптовалют як платіжного засобу, а також ризики, пов’язані із частковим заміщенням офіційних платіжних засобів криптовалютами. Визначено ключові передумови застосування ефективних регулятивних підходів до здійснення операцій з криптовалютами, напрями побудови законодавчо-нормативної бази таких операцій в Україні.
У статті розглянуто особливості фінансової децентралізації в Україні. Досліджено повноваження отримані органами місцевого самоврядування для надання якісних та доступних суспільних послуг громадянам. Також, охарактеризовано відповідальність органів місцевого самоврядування перед виборцями – за ефективність своєї роботи, а перед державою – за її законність. Крім того, досліджено основні джерела ресурсів об’єднаних територіальних громад та проведено групування за критеріями їх сутності та ролі у формуванні конкурентних переваг. Проаналізовано фінансову спроможність громад. Визначено, інші інструменти забезпечення економічного розвитку громади, зокрема, здійснення зовнішніх запозичень, самостійне обрання установ з обслуговування коштів місцевих бюджетів відносно розвитку та власних надходжень бюджетних установ, сформовано теоретико-методологічні положення, які можуть бути покладені в основу сучасної системи управління ресурсоефективністю територіальних громад. Доведено, що добровільно об’єднані територіальні громади мають усі можливості й ресурси для повноцінного функціонування та розвитку. Сьогодні органи місцевої влади беруть на себе цілковиту відповідальність за всі сфери життя на власних територіях, що і є показником успішної й доцільної діяльності ОТГ. Визначено, що за умови добросовісного виконання зобов’язань, підвищується ефективність використання бюджетних коштів, а це – прямий і правильний шлях до стабілізації соціально-економічної ситуації в усій країні. Визначено проблеми з якими стикаються місцеві органи влади на шляху до децентралізації. Проведено аналіз видаткових повноважень органів місцевого самоврядування у сучасних реаліях.
У статті розглянуті особливості інновацій, що лежать в основі технології розподілених реєстрів, її різновиди, потенційні і фактично реалізовані напрями застосування, організаційні форми відповідних проектів. Показано, як ця технологія трансформується в напрямку наближення до централізованих реєстрів, але водночас стимулює удосконалення і модернізацію останніх. Виявлено, що для максимального використання потенціалу ТРР необхідна інтеграція децентралізованих систем з правовим полем і зміна технології не лише у проблемних ланках, що найбільше виграють від її застосування, а й в середовищах, з якими ці ланки взаємодіють. Як свідчить досвід реально запроваджених ТРР-проектів, найбільш успішними з технічних та інституційних причин виявляються платформи, що перебувають десь посередині спектру централізованих і децентралізованих реєстрів, тож втілення радикальної лібертаріанської місії ТРР ще не знайдено – системам потрібний централізований арбітр, координатор, суб’єкт відповідальності і гнучкість, якої можна досягти за допомогою авторитетного втручання в протокол. Зроблено висновок, що навіть максимальне поширення ТРР не означатиме перемогу мереж над ієрархіями і демократизацію: по-перше, тому, що будь-яким мережам властиві процеси подальшої ієрархієзації, а по-друге, відновлення ієрархічного порядку може виявитися необхідним для запобігання сповзанню в анархію.
I. A. Chykarenko, O. O. Chykarenko, А. S. Ushakova
The article identifies the factors, which determine the need for strategic planning of local development in a context of decentralization, namely: reforms or dynamic changes that are taking place today in all spheres of socio-economic and political life in Ukraine; reorientation to new management models due to the need for clear goal-setting and development of projects and programs for achieving goals; amalgamation of communities puts forward the need to create a methodological basis for the independent decision-making on a strategic choice of ways of development, etc. The research is based on the experience of designing and implementing strategies and projects for the development of the amalgamated territorial communities of Dnipropetrovs’k Oblast in which the authors of the publication participated as expert-consultants. The role and specific features of the strategic development management process of the amalgamated territorial communities are described. The corresponding principles of management of the implementation of the strategy of development of the amalgamated territorial community (in particular, providing a meaningful relationship between the strategy and other planning documents; timeliness and prevention; personal responsibility; openness and transparency for the public; current scientific and communication support for the implementation of the strategy; etc.) as well as the role of certain processes and functions in managing the implementation of the strategy are substantiated. The paper shows the importance of the multi-level system of personal responsibility for implementation of strategic priorities - from carrying out of each project from the corresponding portfolio of projects of strategic priorities implementation to responsibility for implementation of the strategy as a whole. In order to ensure efficient management of the strategy implementation, a separate authorized body - Strategy Implementation Management Committee (SIMC) - is suggested to be formed. The functions of the SIMC in the amalgamated territorial communities, which differ in content from the functions of other authorized bodies (working group, strategic committee, etc.) traditionally created to manage the implementation of the strategy of local (regional) development are described. It is grounded the necessity of monitoring and adjusting of certain parameters of the strategy (goals, set of projects, financing, terms of implementation, executors, and expected results, etc.) in case of changes, for example, external environment, loss of relevance of certain strategic or operational goals (projects) or, conversely, new goals (projects), etc. An algorithm for making changes to the strategy summary document is described.
Blockchain is a decentralized transaction and data management solution, the technological weapon-of-choice behind the success of Bitcoin and other cryptocurrencies. As the number and variety of existing blockchain implementations continues to increase, adopters should focus on selecting the best one to support their decentralized applications (dApps), rather than developing new ones from scratch. In this paper we present a framework to aid software architects, developers, tool selectors and decision makers to adopt the right blockchain technology for their problem at hand. The framework exposes the correlation between technological decisions and architectural features, capturing the knowledge from existing industrial products, technical forums/blogs, experts' feedback and academic literature; plus our own experience using and developing blockchain-based applications. We validate our framework by applying it to dissect the most outstanding blockchain platforms, i.e., the ones behind the top 10 cryptocurrencies apart from Bitcoin. Then, we show how we applied it to a real-world case study in the insurtech domain.
Abstract This article explores ‘smart contracts’ from first principles: What they are, whether they are properly called ‘contracts’, and what issues they raise for national contract law. A ‘smart’ contract purports to record contractual promises in language which is both intelligible to human beings and (ultimately) executable by machines. The formalisation of contracting language that this entails is, I argue, the most important aspect for lawyers—just as important as the automation of contractual performance. Rather than taking a doctrinal approach focused on the presence of traditional indicia of contract formation, I examine the nature of contracts as legal entities created by words and documents. In most cases, smart contracts will be ‘wrapped in paper’ and nested in a national legal system. Borrowing from the idiom of computer science, I introduce the term ‘contract stack’ to highlight the complex nature of contracts as legal entities incorporating different ‘layers’, including speech acts by the parties in both natural and formal languages as well as mandatory legal rules. It is the interactions within this contract stack that will be most important to the development of contract law doctrines appropriate to smart contracts. To illustrate my points, I explore a few issues that smart contracts might raise for English contract law. I touch on the questions of illegality, jurisdiction, and evidence, but my focus in this paper is on exploring issues in contract law proper. This contribution should be helpful not only to lawyers attempting to understand smart contracts, but to those involved in coding smart contracts—and writing the languages used to code them.
Fatih Ceylan, Ramazan Eki̇nci̇, Osman Tüzün, Hakan Kahyaoğlu
Başta Bitcoin olmak üzere kripto paralar son dönemde çok sık kullanılmaya başlamıştır. “Para birimi” olarak ve “Değer birikim aracı” olarak kabul görmeye başlayan kripto paraların fiyat hareketlerinin analiz edilmesi ihtiyacı ortaya çıkmıştır. Bu piyasaların büyümesi ve küresel entegrasyonu ile birlikte fiyatlarda meydana gelen önemli değişimlerin temelinde spekülatif balonların olup olmadığı finansal istikrar konusunda açıklık ve güvence açısından önem arz etmektedir. Ayrıca kripto para piyasasında meydana gelen spekülatif hareketler piyasa katılımcılarının sürü psikolojisiyle hareket edip etmedikleri sorusunu ortaya çıkarmaktadır. Bu nedenle çalışmada Bitcoin ve Etherium para birimlerinde spekülatif balonların varlığı Philips vd. (2015) tarafından geliştirilen yöntem ile tespit edilmiş ve ne zaman oluştukları tahminlenmiştir. Piyasada balonların olması ve bu balonların süre olarak varlığı sürü psikolojisinin olduğu yönünde bilgi sağlarken, bu piyasada dengeleyici bir spekülasyonun olmadığı yönünde de bir bilgidir. Elde edilen bulgular doğrultusunda Bitcoin ve Etherium kripto para birimlerinde çok sayıda baloncuk olduğu tespit edilmiştir. Özellikle 2017-2018 yılları arasında büyük baloncukların ortaya çıkması bu para birimlerinin spekülatif hareketlere karşı eğilimli olduğunu gösterilmiştir.
The requirement of supporting both latency sensitive and computing intensive Internet of Things (IoT) applications is consistently boosting the necessity for integrating Edge, Fog and Cloud infrastructure. Although there are a number of real-world frameworks attempt to support such integration, they have many limitations from various perspectives including platform independence, security, resource management and multi-application assistance. To address these limitations, we propose a simplified but effective framework, named FogBus for facilitating end-to-end IoT-Fog(Edge)-Cloud integration. FogBus offers a platform independent interface to IoT applications and computing instances for execution and interaction. It not only assists developers in building applications but also helps users in running multiple applications at a time and service providers to manage their resources. In addition, FogBus applies Blockchain, authentication and encryption techniques to secure operations on sensitive data. Because of its lightweight and cross platform software systems, it is easy to deploy, scalable and cost e_cient. We demonstrate the effectiveness of our framework by creating a computing environment with it that integrates finger pulse oximeter as IoT devices with Smartphone-based gateway and Raspberry Pi-based Fog nodes for Sleep Apnea analysis. We also run several experiments on this computing environment varying FogBus settings. The experimental results show that different FogBus settings can improve latency, energy, network and CPU usage of the computing infrastructure.
Elections conducted on paper consume a lot of resources and contribute to the destruction of forests, which leads to climate deterioration. Moreover, such election process can make it difficult for some people to vote and it often leads to doubts in the validity of counting, in people submitting multiple votes, in ineligible people voting. In several well-known previous examples, doubts in the validity of paper elections lead to the need of recounting and even court battles to decide the validity of the outcome. Having a way to vote online could be an easier and more reliable solution. However, secure and verifiable methods of online voting need to be developed to achieve this.<br><br>Recent online voting experiences in countries such as the United States, India and Brazil demonstrated that further research is needed to improve security guarantees for future elections, to ensure the confidentiality of votes and enable the verification of their integrity and validity. Electronic voting, to be successful, requires a more transparent and secure approach, than the approach that is offered by current electronic voting protocols. Advanced security methods are necessary to introduce effective online voting in the whole world.<br><br>Currently, most online voting systems are centralized, which means that they involve central tallying authorities to take responsibility for verifying, tallying and publishing the final outcome of the election. These previous systems always assume that their central authorities are honest. Otherwise, the published final outcome cannot be trusted. The aim of our new research is to propose and investigate a decentralized ranked choice online voting systems, which never rely on any third party (such as tallying authorities), thereby significantly increasing the confidence and trust of the voters.<br><br>The thesis presents several publicly verifiable online voting systems and indicates the processing steps and stages in the development of a publicity verifiable online voting system from centralized to semi-decentralized, to fully decentralized. By using Homomorphic cryptosystem, proof of zero knowledge and Blockchain technology, the proposed system in this thesis can achieve the following: (1) Flexible voting mechanism: voters can easily rank all candidates; (2) Publicity verifiable: the whole election procedure is transparent and verifiable by voters; (3) Self-tallying: the final outcome of the election can be computed by any individual voter; and (4) Fully decentralized: no tallying authority (or any other trusted third party) involved at all.<br><br>The proposed systems presented in this thesis include protocols developed on Blockchain technology. The technology that is used as the basis for a secure online voting system is ``smart contract over Blockchain', which offers a factor of the integrity of votes and has not been deeply studied in Blockchain technologies to date. The proposed voting protocols ensure confidentiality and preserve the voters' privacy while keeping the election procedures transparent and secure. The underlying Blockchain protocol has not been modified in any way, the voting scheme proposed merely offers an alternative use case of the protocol at hand, which could be presented as the basis for voting systems using Blockchain with further development of the underlying Blockchain protocols.<br><br>
Pedro Marcos, Marco Chiesa, Lucas Fernando Müller, Pradeeban Kathiravelu · 7 authors
Autonomous Systems (ASes) can reach hundreds of networks via Internet eXchange Points (IXPs), allowing improvements in traffic delivery performance and competitiveness. Despite the benefits, any pair of ASes needs first to agree on exchanging traffic. By surveying 100+ network operators, we discovered that most interconnection agreements are established through ad-hoc and lengthy processes heavily influenced by personal relationships and brand image. As such, ASes prefer long-term agreements at the expense of a potential mismatch between actual delivery performance and current traffic dynamics. ASes also miss interconnection opportunities due to trust reasons. To improve wide-area traffic delivery performance, we propose Dynam-IX, a framework that allows operators to build trust cooperatively and implement traffic engineering policies to exploit the rich interconnection opportunities at IXPs quickly. Dynam-IX offers a protocol to automate the interconnection process, an intent abstraction to express interconnection policies, a legal framework to digitally handle contracts, and a distributed tamper-proof ledger to create trust among ASes. We build and evaluate a Dynam-IX prototype and show that an AS can establish tens of agreements per minute with negligible overhead for ASes and IXPs.
Thomas Hepp, Alexander Schoenhals, Christopher Gondek, Béla Gipp
Abstract Currently, timestamps are certified by central timestamping authorities, which have disadvantages of centralization. The concept of the decentralized trusted timestamping (DTT) was developed by Gipp et al. to address these drawbacks. The paper provides insights into the architecture and implementation of a decentralized timestamp service taking the integration of multiple blockchain types into account. Furthermore, the components are introduced and the versatile application scenarios are presented. A future direction of research is the evaluation of blockchain technology and their suitability for timestamping.
Fatih Ceylan, Ramazan Eki̇nci̇, Osman Tüzün, Hakan Kahyaoğlu
Cryptocurrencies, especially Bitcoin, have been used very often recently. The need for analyzing the price movements of the cryptocurrencies, which are accepted as “a currency” and “a store of value”, has emerged. With the growth and global integration of these markets, whether there are speculative bubbles on the basis of significant changes in prices is important in terms of openness and security in respect of financial stability. In addition, speculative movements in the cryptocurrencies market raise the question of whether market participants act with herd mentality. For this reason, in the study, the presence of speculative bubbles in Bitcoin and Etherium is analyzed by using Philips et al. (2015) method and estimated when they were formed. While the presence of bubbles in the cryptocurrencies market and the existence of these bubbles as a duration of herd mentality, it is also known that there is no balancing speculation in this market. According to the findings, a large number of bubbles were found in the Bitcoin and Etherium cryptocurrencies. The emergence of large bubbles, especially between the years 2017-2018, has shown that these cryptocurrencies are prone to speculative movements.