This paper provides the necessary technical background to understand basic Bitcoin operations and documents a set of empirical regularities related to Bitcoin usage. We present the micro-structure of the Bitcoin transaction process and highlight the use of cryptography for the purposes of transaction security and distributed maintenance of a ledger. Using publicly available transaction-level data, we examine patterns of general usage together with usage by Satoshi Dice, the largest online gambling service using Bitcoin as the method of payment. Our analysis suggests that less than 50 percent of all bitcoins in circulation are used in transactions. About half of these transactions involve less than U.S.$100 equivalent, and for the period for which we have data for Satoshi Dice, most of these small-value transactions were related to the online gambling service. Relatively less frequent large value transactions drive the average transaction value to levels above U.S.$40,00 0 equivalent value, and are not likely to involve payments for goods and services. Bitcoin exchange rates exhibit somewhat complicated dynamics. In the past 24 months, the USD-BTC exchange rate increased more than 50-fold. The daily variance of the USD-BTC exchange rate remained remarkably stable for this same period, once the variance calculations account for the changing exchange rate level. We also document that the exchange rates between bitcoin and other major currencies are not well aligned. We interpret this as lack of depth of the exchange markets and as costly exchange rather than as unexploited arbitrage opportunities. Finally, we examine the economic incentives for the participants in the distributed implementation of the Bitcoin scheme.
The next major wave of Bitcoin regulation will likely be aimed at financial instruments, including securities and derivatives, as well as prediction markets and even gambling. While there are many easily regulated intermediaries when it comes to traditional securities and derivatives, emerging bitcoin-denominated instruments rely much less on traditional intermediaries such as banks and securities exchanges. Additionally, the block chain technology that Bitcoin introduced for the first time makes completely decentralized markets and exchanges possible, thus eliminating the need for intermediaries in complex financial transactions. In this Article we survey the type of financial instruments and transactions that will most likely be of interest to regulators, including traditional securities and derivatives, new bitcoin-denominated instruments, and completely decentralized markets and exchanges. We find that Bitcoin derivatives would likely not be subject to the full scope of regulation under the Commodity Exchange Act to the extent that such derivatives involve physical delivery (as opposed to cash settlement) or are non-fungible and not independently traded. We also find that some laws, including those aimed at online gambling, do not contemplate a payment method like Bitcoin, thus placing many transactions in a legal gray area. Following the approach to virtual currencies taken by the Financial Crimes Enforcement Network, we argue that other financial regulators should consider exempting or excluding certain financial transactions denominated in Bitcoin from the full scope of their regulations, much like private securities offerings and forward contracts are treated. We also suggest that to the extent that regulation and enforcement becomes more costly than its benefits, policymakers should consider and pursue strategies consistent with that new reality, such as efforts to encourage resilience and adaptation by existing institutions.
At present, bitcoin is held mostly as a speculative vehicle, little used to pay for goods and services. Its value has been unstable, which impedes bitcoinâs wider use as a payment medium. We explain why the value of bitcoin has been so unstable. Then, we discuss entrepreneurial efforts that might enable bitcoin to become a more commonly accepted payment medium.
The complexity and interdependence of the economies of various geographical and political entities have one generic binder - money. The economic history of the last century, replicated in the first decade of our century, can be âwrittenâ with money. Indeed, money, a multiple discovery of the civilization in its historical way, was and still is the guardian of hope for prosperity. The disputes about money clearly indicate the need, opportunity and the possibility of monetary competition, which would provide, from the point of view of entrepreneurs, the most suitable production of money based on expectations of their economic preferences. Increasingly more, theorists, practitioners and analysts bring to the fore the issue of simultaneously using the official currency and the digital one. Thus, the issue of the public debate regarding the private money is still of interest. Based on these considerations, this paper aims to highlight how the digital currency Bitcoin can meet the challenges of the economic environment, taking into account both the opportunities and the threats to which it is subject, and the records emphasized by the history of economic thought and adapted to the current reality.
I will address eight common claims about bitcoin: 1. Physical bitcoins exist; 2. The founder of bitcoin is a person called Satoshi Nakamoto; 3. Bitcoin is mainly used for criminal activity; 4. A lack of security plagues bitcoin; 5. Mining is a waste of energy; 6. Bitcoin too small today to be an important economic force; 7. Bitcoin is currently too volatile to be viable; 8. Bitcoin is just another currency. For additional details beyond "Bitcoin Myths and Facts," I have another paper/slidedeck called "Cryptofinance" that goes deeper into the mechanics of cryptocurrencies. It is available at http://ssrn.com/abstract=2438299 .
Bitcoin is a peer-to-peer (P2P) payment network running on a cryptographic protocol. Nodes of Bitcoin communicate to each other by broadcasting digitally signed messages to the network. Transactions are listed in a distributed, decentralized, public database referred to as the block, using a proof of work to reach consensus. The term âBitcoin networkâ refers to a set of nodes running the P2P protocol. The structure of the Bitcoin network is minimal with a decentralized network of volunteers. This chapter presents the overall process of Bitcoin networks including transactions, digital signatures, relay networks, and Bitcoin script.
Arthur Gervais, SrÄjan Äapkun, Ghassan Karame, Damian Gruber
Lightweight Bitcoin clients are gaining increasing adoption among Bitcoin users, owing to their reduced resource and bandwidth consumption. These clients support a simplified payment verification (SPV) mode as they are only required to download and verify a part of the block chain---thus supporting the usage of Bitcoin on constrained devices, such as smartphones. SPV clients rely on Bloom filters to receive transactions that are relevant to their local wallet. These filters embed all the Bitcoin addresses used by the SPV clients, and are outsourced to more powerful Bitcoin nodes which then only forward to those clients transactions relevant to their outsourced Bloom filters. \n \nIn this paper, we explore the privacy of existing SPV clients. We show analytically and empirically that the reliance on Bloom filters within existing SPV clients leaks considerable information about the addresses of Bitcoin users. Our results show that an SPV client who uses a modest number of Bitcoin addresses (e.g., < 20) risks revealing almost all of his addresses. We also show that this information leakage is further exacerbated when users restart their SPV clients and/or when the adversary has access to more than one Bloom filter pertaining to the same SPV client. Motivated by these findings, we propose an efficient countermeasure to enhance the privacy of users which rely on SPV clients; our proposal can be directly integrated within existing SPV client implementations.
The anonymity of Bitcoin prevents analysis of its users. We collect Google Trends data to examine determinants of interest in Bitcoin. Based on anecdotal evidence regarding Bitcoin users, we construct proxies for four possible clientele: computer programming enthusiasts, speculative investors, Libertarians and criminals. Computer programming and illegal activity search terms are positively correlated with Bitcoin interest, while Libertarian and investment terms are not.
Joshua R. Hendrickson, Thomas L. Hogan, William J. Luther
The recent proliferation of bitcoin has been a boon for users but might pose problems for governments. Indeed, some governments have already taken steps to ban or discourage the use of bitcoin. In a model with endogenous matching and random consumption preferences, we find multiple monetary equilibria including one in which bitcoin coexists with official currency. We then identify the conditions under which government transactions policy might deter the use of bitcoin. We show that such a policy becomes more difficult if some users strictly prefer bitcoin because they can avoid other users holding the official currency in the matching process. ( JEL C78, E41, E42, E50)
In Bitcoin, transaction malleability describes the fact that the signatures that prove the ownership of bitcoins being transferred in a transaction do not provide any integrity guarantee for the signatures themselves. This allows an attacker to mount a malleability attack in which it intercepts, modifies, and rebroadcasts a transaction, causing the transaction issuer to believe that the original transaction was not confirmed. In February 2014 MtGox, once the largest Bitcoin exchange, closed and filed for bankruptcy claiming that attackers used malleability attacks to drain its accounts. In this work we use traces of the Bitcoin network for over a year preceding the filing to show that, while the problem is real, there was no widespread use of malleability attacks before the closure of MtGox.
We study a model of fairness in secure computation in which an adversarial party that aborts on receiving output is forced to pay a mutually predefined monetary penalty. We then show how the Bitcoin network can be used to achieve the above notion of fairness in the two-party as well as the multiparty setting (with a dishonest majority). In particular, we propose new ideal functionalities and protocols for fair secure computation and fair lottery in this model. One of our main contributions is the definition of an ideal primitive, which we call F?CR (CR stands for âclaim-or-refundâ), that formalizes and abstracts the exact properties we require from the Bitcoin network to achieve our goals. Naturally, this abstraction allows us to design fair protocols in a hybrid model in which parties have access to the F?CR functionality, and is otherwise independent of the Bitcoin ecosystem. We also show an efficient realization of F?CR that requires only two Bitcoin transactions to be made on the network. Our constructions also enjoy high efficiency. In a multiparty setting, our protocols only require a constant number of calls to F?CR per party on top of a standard multiparty secure computation protocol. Our fair multiparty lottery protocol improves over previous solutions which required a quadratic number of Bitcoin transactions.