Pedro Bonillo Bueno, Emilio Aragon Fortes, Konstantinos Vlachoski
Since its launch in 2008, Bitcoin becomes one of the most successful and fast-growing alternative currencies. As of 2017, the market capitalization is around $46 billion and arguably expected to continue growing. The Bitcoin to the US dollar exchange rate has been very volatile and fluctuating significantly. Although Bitcoin was designed as a medium of exchange, it is now more as an investment tool and thus the development of effective quantitative risk management tools becomes quite urgent for all the market participants. In this paper, we investigate empirical distribution of the Bitcoin exchange rate returns by using four types of widelyused heavy-tailed distribution and show that the Skewed t distribution has the best empirical performance. We further calculate the VaR based risk measures and found the Skewed t distribution generates the VaR values, which are closest to historical VaR values. Our results could be directly used in the industry’s stress testing practice, and help financial institutions fulfill the regulatory requirements.
Cüneyt Gürcan Akçora, Yulia R. Gel, Murat Kantarcıoğlu
Bitcoin and its underlying technology, blockchain, have gained significant popularity in recent years. Satoshi Nakamoto designed Bitcoin to enable a secure, distributed platform without the need for central authorities, and blockchain has been hailed as a paradigm that will be as impactful as Big Data, Cloud Computing, and Machine Learning. Blockchain incorporates innovative ideas from various fields, such as public-key encryption and distributed systems. As a result, readers often encounter resources that explain Blockchain technology from a single perspective, leaving them with more questions than answers. In this primer, we aim to provide a comprehensive view of blockchain. We will begin with a brief history and introduce the building blocks of the blockchain. As graph mining is a major area of blockchain analysis, we will delve into the graph-theoretical aspects of Blockchain technology. We will also discuss the future of blockchain and explain how extensions such as smart contracts and decentralized autonomous organizations will function. Our goal is to provide a concise but complete description of blockchain technology that is accessible to readers with no prior expertise in the field.
We’ve seen repeatedly that ideas in the research literature can be gradually forgotten or lie unappreciated, especially if they are ahead of their time, even in popular areas of research. Both practitioners and academics would do well to revisit old ideas to glean insights for present systems. Bitcoin was unusual and successful not because it was on the cutting edge of research on any of its components, but because it combined old ideas from many previously unrelated fields. This is not easy to do, as it requires bridging disparate terminology, assumptions, etc., but it is a valuable blueprint for innovation.
The article is aimed at studying the history of origins, the preconditions for development, the main problems of functioning, and the prospects of legalizing the cryptocurrency market in Ukraine. One of the key risks when implementing advances of the IT in the financial sphere is the possibility of physical disappearance of banking system in its classical form because of its inability to compete with new technologies. The most troubling, versus the classical banks, may be considered such new technologies as credit electronic platforms and blockchain. In the recent time the bitcoin course has been growing rapidly, giving all the reasons to consider it primarily a classical «pyramid scheme». The cryptocurrency market may also be characterized a «pyramid scheme» because of the fact that the course of such a currency has not any coverage except increase in the number of participants and investors. Ukraine is not a leader in the international cryptocurrency market, albeit not an outsider. In order to secure a reliable State control of the «gray» cryptocurrency market, which is actually present in Ukraine, the article suggests some necessary actions directed towards legalizing and ordering this phenomenon.
The most fundamental purpose of blockchain technology is to enable persistent, consistent, distributed storage of information. Increasingly common are authentication systems that leverage this property to allow users to carry their personal data on a device while a hash of this data is signed by a trusted authority and then put on a blockchain to be compared against. For instance, in 2015, MIT introduced a schema for the publication of their academic certificates based on this principle. In this work, we propose a way for users to obtain assured identities based on face-to-face proofing that can then be validated against a record on a blockchain. Moreover, in order to provide anonymity, instead of storing a hash, we make use of a scheme of Brands to store a commitment against which one can perform zero-knowledge proofs of identity. We also enforce the confidentiality of the underlying data by letting users control a secret of their own. We show how our schema can be implemented on Bitcoin's blockchain and how to save bandwidth by grouping commitments using Merkle trees to minimize the number of Bitcoin transactions that need to be sent. Finally, we describe a system in which users can gain access to services thanks to the identity records of our proposal.
Bitcoin, a protocol for a new permissionless decentralized digital currency hailed the arrival of a new application domain for computer science. Following Bitcoin's arrival, a series of innovations derived from the state of the art in several fields has been applied to cryptocurrencies, and has been slowly reshaping monetary and financial instruments on public distributed ledgers. It was soon clear however that Bitcoin and similar cryptocurrencies still require additional improvements. This challenging domain presents researchers in the field with new and exciting questions. I provide examples from two main research threads, related to the scalability of the protocol and to its underlying incentives.
With recent alarm and focus on Bitcoin , many researchers tried to come up with studies that are related to Bitcoin. This paper tries to do the same but with a focus on the area of Islamic finance. We try to relate Bitcoin and Islamic index to find if there is any relation between these two assets and to find which will stand out if they are put in one portfolio. Since both assets are deemed to be of high risk in nature, it is an interesting topic to be investigated especially if they are put together. This analysis was carried out using the standard time-series approach of cointegration, VECM and VDC. The empirical results evidenced that Bitcoin and Islamic index are theoretically related as they are cointegrated. Another interesting finding in this study unveiled that Islamic index will be more influential than Bitcoin if they are put in one portfolio.
Although Bitcoin has long been dominant in the crypto scene, it is certainly not alone. Ether is another cryptocurrency related project that has attracted an intensive attention because of its additional features. This study seeks to test whether these cryptocurrencies differ in terms of their volatile and speculative behaviors, hedge, safe haven and risk diversification properties. Using different econometric techniques, we show that a) Bitcoin and Ether are volatile and relatively more responsive to bad news, but the volatility of Ether is more persistent than that of Bitcoin; b) for both cryptocurrencies, the exuberance and the collapse of bubbles were identified, but Bitcoin appears more speculative than Ether; c) there is negative and significant correlation between Bitcoin/Ether and other assets (S\&P500 stocks, US bonds, oil), which would indicate that digital currencies can hedge against the price movements of these assets; d) there is negative tail independence between Bitcoin/Ether and other financial assets, implying that these cryptocurrencies exhibit the function of a weak safe haven; and e) The inclusion of Bitcoin/ Ether in a portfolio improve its efficiency in terms of higher reward-to-risk ratios. But investors who hold diversified portfolios made of stocks or bonds and Ether may face losses over bearish regime. In such situation, stock and bond investors may take a short position on Bitcoin.
At the heart of the Bitcoin is a blockchain protocol, a protocol for achieving consensus on a public ledger that records bitcoin transactions. To the extent that a blockchain protocol is used for applications such as contract signing and making certain transactions (such as house sales) public, we need to understand what guarantees the protocol gives us in terms of agents' knowledge. Here, we provide a complete characterization of agent's knowledge when running a blockchain protocol using a variant of common knowledge that takes into account the fact that agents can enter and leave the system, it is not known which agents are in fact following the protocol (some agents may want to deviate if they can gain by doing so), and the fact that the guarantees provided by blockchain protocols are probabilistic. We then consider some scenarios involving contracts and show that this level of knowledge suffices for some scenarios, but not others.
Using 1-min returns of Bitcoin prices, we investigate statistical properties and multifractality of a Bitcoin time series. We find that the 1-min return distribution is fat-tailed, and kurtosis largely deviates from the Gaussian expectation. Although for large sampling periods, kurtosis is anticipated to approach the Gaussian expectation, we find that convergence to that is very slow. Skewness is found to be negative at time scales shorter than one day and becomes consistent with zero at time scales longer than about one week. We also investigate daily volatility-asymmetry by using GARCH, GJR, and RGARCH models, and find no evidence of it. On exploring multifractality using multifractal detrended fluctuation analysis, we find that the Bitcoin time series exhibits multifractality. The sources of multifractality are investigated, confirming that both temporal correlation and the fat-tailed distribution contribute to it. The influence of "Brexit" on June 23, 2016 to GBP--USD exchange rate and Bitcoin is examined in multifractal properties. We find that, while Brexit influenced the GBP--USD exchange rate, Bitcoin was robust to Brexit.
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
A new variation of blockchain proof of work algorithm is proposed to incentivize the timely execution of image processing algorithms. A sample image processing algorithm is proposed to determine interesting images using analysis of the entropy of pixel subsets within images. The efficacy of the image processing algorithm is examined using two small sets of training and test data. The interesting image algorithm is then integrated into a simplified blockchain mining proof of work algorithm based on Bitcoin. The incentive of cryptocurrency mining is theorized to incentivize the execution of the algorithm and thus the retrieval of images that satisfy a minimum requirement set forth by the interesting image algorithm. The digital storage implications of running an image- based blockchain are then examined mathematically.
A blockchain is a decentralized ledger where all transactions are recorded. For having a reliable blockchain and double-spending prevention, we need a decentralized consensus and agreement on a blockchain. Bitcoin uses proof-of-work (PoW). It is a cryptographic puzzle that is difficult to solve but easy to verify. However, because of significant latency of proof-of-work for transactions confirmation, this consensus mechanism is vulnerable against double-spending. On the other hand, PoW consumes a significant amount of energy that by growing the network, it becomes a major problematic of this consensus mechanism. In this paper, we introduce an alternative to PoW, because of all its major problems and security issues that may lead to collapsing decentralization of the blockchain, while a full decentralized system is the main purpose of using blockchain technology. The approach we introduce is based on a distributed voting process and called "RDV: Register, Deposit, Vote". Since in RDV algorithm, there is no mining process, so it is appropriate for low-level energy devices and Internet of Things (IoT).
The long-term dependence of Bitcoin (BTC), manifesting itself through a Hurst exponent $H>0.5$, is exploited in order to predict future BTC/USD price. A Monte Carlo simulation with $10^4$ geometric fractional Brownian motion realisations is performed as extensions of historical data. The accuracy of statistical inferences is 10\%. The most probable Bitcoin price at the beginning of 2018 is 6358 USD.
Joshua Lind, Christian Priebe, Divya Muthukumaran, Dan O’Keeffe · 12 authors
Trusted execution support in modern CPUs, as offered by Intel SGX enclaves , can protect applications in untrusted environments. While prior work has shown that legacy applications can run in their entirety inside enclaves, this results in a large trusted computing base (TCB). Instead, we explore an approach in which we partition an applica- tion and use an enclave to protect only security-sensitive data and functions, thus obtaining a smaller TCB. We describe Glamdring , the first source-level parti- tioning framework that secures applications written in C using Intel SGX. A developer first annotates security- sensitive application data. Glamdring then automatically partitions the application into untrusted and enclave parts: (i) to preserve data confidentiality, Glamdring uses dataflow analysis to identify functions that may be ex- posed to sensitive data; (ii) for data integrity, it uses back- ward slicing to identify functions that may affect sensitive data. Glamdring then places security-sensitive functions inside the enclave, and adds runtime checks and crypto- graphic operations at the enclave boundary to protect it from attack. Our evaluation of Glamdring with the Mem- cached store, the LibreSSL library, and the Digital Bitbox bitcoin wallet shows that it achieves small TCB sizes and has acceptable performance overheads.
The long-term dependence of Bitcoin (BTC), manifesting itself through a Hurst\nexponent $H>0.5$, is exploited in order to predict future BTC/USD price. A\nMonte Carlo simulation with $10^4$ geometric fractional Brownian motion\nrealisations is performed as extensions of historical data. The accuracy of\nstatistical inferences is 10\\%. The most probable Bitcoin price at the\nbeginning of 2018 is 6358 USD.\n
General Insurance occupies a strong position in today's market. It has a centralized way of operation, which makes it inefficient, less transparent, with trust problems and creates conflicts of interest between insurance companies and policyholders. Furthermore, it's an industry with relative difficulty in innovation, which contrasts with today's services powered by new technologies. New disruptive technologies have the capacity to compromise the value chain of traditional insurance, creating a big problem in its stability and future. Associated to this new kind of technologies, comes a new way of thinking perpetuated by the new generations based on the new trend of sharing economy. They give priority to new technology based services, which are decentralized, more convenient, more price competitive, transparent, and efficient and they prefer services which put the user more in control instead of the current less personalized options. New business models such as Social Insurance, are being developed and powered by new technologies and this new way of thinking. Social Insurance enables people in need of insurance to connect and pool their money and risks. It offers coverage that is cheaper, more transparent, and more relevant to the customer. Members of this type of insurance are both policyholders and underwriters. All these factors compromise the future of traditional insurance companies and their business model. The main goal is to create a new business model in order to adapt insurance companies to the new trend of shared economy. This new business model is going to be focused on health insurance, based in peer to peer communication and is going to be backed up by a business case and a prototype powered by a blockchain database. Blockchain is a decentralized transaction ledger shared amongst all nodes participating in the system. Every node has an updated copy of the database and cannot update it without the consensus of the network, removing the need for having a central authority or trusted third party to monitor the system. Each Blockchain implementation may have its own consensus mechanism (e.g. Proof-of-Work and Proof-of-Stake) to ensure that one node on its own cannot change the database without being validated by the network. Bitcoin is the world's most well-known Blockchain implementation, a public ledger for all transactions made in with a digital currency. However, Blockchain technology can be applied to multiple use cases and industries using Smart Contracts (a collection of code that runs on the network) to define the rules of the business. It fits the purpose for this business model, because it has peer to peer communication by default and has no central authority, making the service more efficient and transparent.
Transactions between individuals have always been a part and parcel of human society for the division of labour made people interdependent. The medium of transaction has also been evolving along with the evolution of society and human consciousness from barter system to commodity money to fiat currency and now to digital currency or cryptocurrency. But since evolution is a form of error correction, the problem of double spending in digital currency was solved by a distributed ledger system called Blockchain. Since 2008 onwards the blockchain technology has been separated from bitcoins to be injected to many other problems related especially to banking transactions. Blockchain technology enables the creation of decentralized currencies, smart contracts and intelligent assets that can be controlled over the Internet
Abstract Blockchains are distributed data structures that are used to achieve consensus in systems for cryptocurrencies (like Bitcoin) or smart contracts (like Ethereum). Although blockchains gained a lot of popularity recently, there are only few logic-based models for blockchains available. We introduce $\mathsf{BCL}$, a dynamic logic to reason about blockchain updates, and show that $\mathsf{BCL}$ is sound and complete with respect to a simple blockchain model.
The hype over bitcoins has been compared to the tulip mania in 17th century Netherlands and it has spawned a host of similar cryptocurrencies. As it has gained in popularity, the law has approached the subject warily, mostly from a regulatory perspective. However, no comprehensive consideration of the fundamental nature of a bitcoin owner’s private law relation to his/her/its bitcoins has been properly conducted. Whether or not bitcoins or other cryptocurrencies achieve mainstream adoption or remain of interest to only a niche audience, this question will inevitably have to be properly addressed. This paper proposes to consider if bitcoins might be recognised as the subject of property rights by Commonwealth courts and if so, what such rights ought to entail. It will begin with a careful consideration of the controversial question of the scope of the law of property before considering bitcoin’s place within the law of property (if any). What is the meaning of property in the common law? What fundamental differences exist between tangible and intangible property? If ownership of bitcoins is worthy of protection, what shape should it take? It suggests that the common law adopts a more expansive view of property than civilian systems and that it is thus able to accommodate bitcoins and other cryptocurrencies within its law of property. However, owing to their unusual nature, legal rights to them must take on a unique and unorthodox form. The code underlying Bitcoin also poses particular challenges to the law which this paper also addresses.
Abstract The I owe you (IOU) credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is no different from a cryptocurrency in terms of weak privacy; recent demonstrative deanonymization attacks raise important concerns regarding the privacy of the Ripple users and their transactions. However, unlike for cryptocurrencies, there is no known privacy solution compatible with the existing credit networks such as Ripple. In this paper, we present PathShuffle, the first path mixing protocol for credit networks. PathShuffle is fully compatible with the current credit networks. As its essential building block, we propose PathJoin, a novel protocol to perform atomic transactions in credit networks. Using PathJoin and the P2P mixing protocol DiceMix, PathShuffle is a decentralized solution for anonymizing path-based transactions. We demonstrate the practicality of PathShuffle by performing path mixing in Ripple.