Tracing Transactions Across Cryptocurrency Ledgers

One of the defining features of a cryptocurrency is that its ledger, containing all transactions that have evertaken place, is globally visible. As one consequenceof this degree of transparency, a long line of recent re-search has demonstrated that even in cryptocurrenciesthat are specifically designed to improve anonymity it is often possible to track money as it changes hands,and in some cases to de-anonymize users entirely. With the recent proliferation of alternative cryptocurrencies, however, it becomes relevant to ask not only whether ornot money can be traced as it moves within the ledgerof a single cryptocurrency, but if it can in fact be tracedas it moves across ledgers. This is especially pertinent given the rise in popularity of automated trading platforms such as ShapeShift, which make it effortless to carry out such cross-currency trades. In this paper, weuse data scraped from ShapeShift over a thirteen-monthperiod and the data from eight different blockchains to explore this question. Beyond developing new heuristics and creating new types of links across cryptocurrency ledgers, we also identify various patterns of cross-currency trades and of the general usage of these platforms, with the ultimate goal of understanding whetherthey serve a criminal or a profit-driven agenda.Comment: 14 pages, 13 tables, 6 figure

An Empirical Analysis of Privacy in Cryptocurrencies

Cryptocurrencies have emerged as an important technology over the past decade and have, undoubtedly, become blockchain’s most popular application. Bitcoin has been by far the most popular out of the thousands of cryptocurrencies that have been created. Some of the features that made Bitcoin such a fascinating technology include its transactions being made publicly available and permanently stored, and the ability for anyone to have access. Despite this transparency, it was initially believed that Bitcoin provides anonymity to its users, since it allowed them to transact using a pseudonym instead of their real identity. However, a long line of research has shown that this initial belief was false and that, given the appropriate tools, Bitcoin transactions can indeed be traced back to the real-life entities performing them. In this thesis, we perform a survey to examine the anonymity aspect of cryptocurrencies. We start with early works that made first efforts on analysing how private this new technology was. We analyse both from the perspective of a passive observer with eyes only to the public immutable state of transactions, the blockchain, as well as from an observer who has access to network layer information. We then look into the projects that aimed to enhance the anonymity provided in cryptocurrencies and also analyse the evidence of how much they succeeded in practice. In the first part of our own contributions we present our own take on Bitcoin’s anonymity, inspired by the research already in place. We manage to extend existing heuristics and provide a novel methodology on measuring the confidence we have in our anonymity metrics, instead of looking into the issue from a binary perspective, as in previous research. In the second part we provide the first full-scale empirical work on measuring anonymity in a cryptocurrency that was built with privacy guarantees, based on a very well established cryptography, Zcash. We show that just building a tool which provides anonymity in theory is very different than the privacy offered in practice once users start to transact with it. Finally, we look into a technology that is not a cryptocurrency itself but is built on top of Bitcoin, thus providing a so-called layer 2 solution, the Lightning network. Again, our measurements showed some serious privacy concerns of this technology, some of which were novel and highly applicable

An Empirical Analysis of Anonymity in Zcash

Among the now numerous alternative cryptocurrencies derived from Bitcoin, Zcash is often touted as the one with the strongest anonymity guarantees, due to its basis in well-regarded cryptographic research. In this paper, we examine the extent to which anonymity is achieved in the deployed version of Zcash. We investigate all facets of anonymity in Zcash's transactions, ranging from its transparent transactions to the interactions with and within its main privacy feature, a shielded pool that acts as the anonymity set for users wishing to spend coins privately. We conclude that while it is possible to use Zcash in a private way, it is also possible to shrink its anonymity set considerably by developing simple heuristics based on identifiable patterns of usage.Comment: 27th USENIX Security Symposium (USENIX Security '18), 15 pages, Zcas

An Empirical Analysis of Privacy in the Lightning Network

Payment channel networks, and the Lightning Network in particular, seem to offer a solution to the lack of scalability and privacy offered by Bitcoin and other blockchain-based cryptocurrencies. Previous research has focused on the scalability, availability, and crypto-economics of the Lightning Network, but relatively little attention has been paid to exploring the level of privacy it achieves in practice. This paper presents a thorough analysis of the privacy offered by the Lightning Network, by presenting several attacks that exploit publicly available information about the network in order to learn information that is designed to be kept secret, such as how many coins a node has available or who the sender and recipient are in a payment routed through the network.Comment: 26 pages, 5 figure

Tests on RC Beams Strengthened at the Span with Externally Bonded Polymers Reinforced with Carbon or Steel Fibers

The main objective of the experimental work reported herein is the comparative evaluation of steel-reinforced polymers (SRPs) and carbon-reinforced polymers (CFRPs) used as externally-bonded reinforcement in strengthening of reinforced-concrete (RC) members. Tensile stress strain as well as bond constitutive laws for these materials were first derived from 16 tests and are summarized here. Results are then reported from four-point bending tests of five full-scale RC beams strengthened at their span using SRP and CFRP strips. The bond tests have shown that by providing a bond length greater than the effective one, neither the bond strength nor the deformation capacity are increased, whereas by increasing the width of the strip the bond strength is increased. From the bending tests of beams it was found that the use of both SRP and CFRP strips resulted in a significant increase in strength (up to 92%) with respect to the strength of the initial specimen. The experimentally measured strengths were estimated analytically using both the experimental measurements of the specimen deformations and the pertinent provisions of standards from the American Concrete Institute and the European Committee for Standardization

The dilemma of providing cardioverter/defibrillator back-up for all patients with heart failure eligible for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) achieved by biventricular pacing (CRT-P) has been proved to improve symptoms and prognosis of patients with refractory heart failure. Sudden cardiac death is quite common among patients with symptomatic heart failure and implantable cardioverter-defibrillator (ICD) therapy has been proved to effectively reduce sudden deaths in heart failure patients. Given the results of the recently published primary prevention trials and the high incidence of sudden cardiac death among CRT-P recipients, CRT combined with backup defibrillator therapy (CRT-D) seems a logical therapeutic option in patients eligible for CRT. However, the apparent beneficial effects of such an appealing combination do not alleviate the skepticism about the unselected use of CRT-D therapy. This skepticism is largely related to the high cost of this method, to the limited availability of human and financial resources and to our inability to appropriately define the selection criteria for CRT candidates, which are expected to influence the clinicians??? decisions when confronted with the dilemma of providing CRT-D therapy for all patients eligible for CRT

Individualized Tailoring of Hypolipidemic Pharmacological Treatment

The validation of the lipid hypothesis, which pertains to the relationship between dyslipidemia and atherogenesis, has established the central role of hypolipidemic treatment in the frontline of primary and secondary prevention of coronary artery disease. However, the complexity of the lipoprotein disorders, which are usually associated with more than one biochemical abnormalities, and the availability of several hypolipidemic agents in the existing therapeutic armamentarium with combined beneficial effects of variable intensity on several lipoproteins, have stressed the need for the development and implementation of easily applicable therapeutic algorithms which will enable the individualized tailoring of hypolipidemic management with maximal efficiency and safety. One such algorithm of individualized tailoring of hypolipidemic therapy is being proposed in this brief overview

The Relation of Migraine Headaches and Interatrial Shunts

Foramen ovale plays a very important role in fetal circulation by bypassing the lungs and diverting circulation from the right to the left heart. With birth it is usually sealed; however, probe patent or incompletely sealed foramen ovale remains in approximately 25% of adults. Patent foramen ovale (PFO) acquires significance in various congenital heart diseases or other particular settings leading to a right to left shunt, and thus to paradoxical embolism. PFO has been associated with transient ischemic attacks or cryptogenic strokes and also a host of other problems, including migraine. The recognition of an association between migraine syndrome with aura and PFO appears to have come ???full circle??? over the past two decades. Epidemiologic studies have suggested a notably increased PFO prevalence in persons suffering from migraine.The prevalence of migraine headache is higher in cryptogenic stroke patients with PFO than in the general population. Studies have suggested that closure of the PFO may reduce migrainous symptoms. The relation between this association and the recognition of migraine as a risk factor for ischemic stroke in the young is unclear, though right to left passage of circulating factors has been postulated in both syndromes. Despite case series and uncontrolled studies documenting beneficial effects of PFO closure in patients with migraine, particularly those also afflicted by cryptogenic stroke, the recommendation for PFO closure in patients with migraine alone will need to await the results of ongoing randomized trials

Genome-wide association analysis of susceptibility and clinical phenotype in multiple sclerosis

Multiple sclerosis (MS), a chronic disorder of the central nervous system and common cause of neurological disability in young adults, is characterized by moderate but complex risk heritability. Here we report the results of a genome-wide association study performed in a 1000 prospective case series of well-characterized individuals with MS and group-matched controls using the Sentrix® HumanHap550 BeadChip platform from Illumina. After stringent quality control data filtering, we compared allele frequencies for 551 642 SNPs in 978 cases and 883 controls and assessed genotypic influences on susceptibility, age of onset, disease severity, as well as brain lesion load and normalized brain volume from magnetic resonance imaging exams. A multi-analytical strategy identified 242 susceptibility SNPs exceeding established thresholds of significance, including 65 within the MHC locus in chromosome 6p21.3. Independent replication confirms a role for GPC5, a heparan sulfate proteoglycan, in disease risk. Gene ontology-based analysis shows a functional dichotomy between genes involved in the susceptibility pathway and those affecting the clinical phenotyp