53 research outputs found
Towards Creating a Thin Client for Monero
As an increasing number of users begin to use cryptocurrencies, the number
of transactions per day has also been steadily increasing. Users traditionally
run full nodes which involve downloading a copy of the blockchain associated
with that cryptocurrency and updating it through the network. This
method guarantees full security at the cost of greater power consumption
and data storage. The recent ubiquity of data connections and
low-capacity
hardware such as smartphones has only furthered the demand to delegate
cryptocurrency-related computations to capable servers. This raises the need
to verify results that are returned to a light client by a server, and also to
perform conflict
resolutions whenever servers disagree upon a query. In this
study, we implement the storage of the Monero blockchain as authenticated
data structures on powerful servers, and perform computations on the data
structures as queries are made or as the blockchain is updated. Experimental
results have shown that authenticated data structures can be used to create
a secure thin client for Monero, and we conclude with a discussion on the
possibility of integrating that thin client into the network.Ope
SoK: Log Based Transparency Enhancing Technologies
This paper systematizes log based Transparency Enhancing Technologies. Based
on established work on transparency from multiple disciplines we outline the
purpose, usefulness, and pitfalls of transparency. We outline the mechanisms
that allow log based transparency enhancing technologies to be implemented, in
particular logging mechanisms, sanitisation mechanisms and the trade-offs with
privacy, data release and query mechanisms, and how transparency relates to the
external mechanisms that can provide the ability to contest a system and hold
system operators accountable. We illustrate the role these mechanisms play with
two case studies, Certificate Transparency and cryptocurrencies, and show the
role that transparency plays in their function as well as the issues these
systems face in delivering transparency
SoK: Layer-Two Blockchain Protocols
Blockchains have the potential to revolutionize markets and services. However, they currently exhibit high latencies and fail to handle transaction loads comparable to those managed by traditional financial systems. Layer-two protocols, built on top of layer-one blockchains, avoid disseminating every transaction to the whole network by exchanging authenticated transactions off-chain. Instead, they utilize the expensive and low-rate blockchain only as a recourse for disputes. The promise of layer-two protocols is to complete off-chain transactions in sub-seconds rather than minutes or hours while retaining asset security, reducing fees and allowing blockchains to scale.
We systematize the evolution of layer-two protocols over the period from the inception of cryptocurrencies in 2009 until today, structuring the multifaceted body of research on layer-two transactions. Categorizing the research into payment and state channels, commit-chains and protocols for refereed delegation, we provide a comparison of the protocols and their properties. We provide a systematization of the associated synchronization and routing protocols along with their privacy and security aspects. This Systematization of Knowledge (SoK) clears the layer-two fog, highlights the potential of layer-two solutions and identifies their unsolved challenges, indicating propitious avenues of future work
Cybersecurity applications of Blockchain technologies
With the increase in connectivity, the popularization of cloud services, and the rise
of the Internet of Things (IoT), decentralized approaches for trust management
are gaining momentum. Since blockchain technologies provide a distributed ledger,
they are receiving massive attention from the research community in different application
fields. However, this technology does not provide cybersecurity by itself.
Thus, this thesis first aims to provide a comprehensive review of techniques and
elements that have been proposed to achieve cybersecurity in blockchain-based systems.
The analysis is intended to target area researchers, cybersecurity specialists
and blockchain developers. We present a series of lessons learned as well. One of
them is the rise of Ethereum as one of the most used technologies.
Furthermore, some intrinsic characteristics of the blockchain, like permanent
availability and immutability made it interesting for other ends, namely as covert
channels and malicious purposes.
On the one hand, the use of blockchains by malwares has not been characterized
yet. Therefore, this thesis also analyzes the current state of the art in this area. One
of the lessons learned is that covert communications have received little attention.
On the other hand, although previous works have analyzed the feasibility of
covert channels in a particular blockchain technology called Bitcoin, no previous
work has explored the use of Ethereum to establish a covert channel considering all
transaction fields and smart contracts.
To foster further defence-oriented research, two novel mechanisms are presented
on this thesis. First, Zephyrus takes advantage of all Ethereum fields and smartcontract
bytecode. Second, Smart-Zephyrus is built to complement Zephyrus by
leveraging smart contracts written in Solidity. We also assess the mechanisms feasibility
and cost. Our experiments show that Zephyrus, in the best case, can embed
40 Kbits in 0.57 s. for US 1.82 per bit), the provided stealthiness might be worth the price for attackers. Furthermore,
these two mechanisms can be combined to increase capacity and reduce
costs.Debido al aumento de la conectividad, la popularización de los servicios en la nube
y el auge del Internet de las cosas (IoT), los enfoques descentralizados para la
gestión de la confianza están cobrando impulso. Dado que las tecnologías de cadena
de bloques (blockchain) proporcionan un archivo distribuido, están recibiendo
una atención masiva por parte de la comunidad investigadora en diferentes campos
de aplicación. Sin embargo, esta tecnología no proporciona ciberseguridad por sí
misma. Por lo tanto, esta tesis tiene como primer objetivo proporcionar una revisión
exhaustiva de las técnicas y elementos que se han propuesto para lograr la ciberseguridad
en los sistemas basados en blockchain. Este análisis está dirigido a investigadores
del área, especialistas en ciberseguridad y desarrolladores de blockchain. A
su vez, se presentan una serie de lecciones aprendidas, siendo una de ellas el auge
de Ethereum como una de las tecnologías más utilizadas.
Asimismo, algunas características intrínsecas de la blockchain, como la disponibilidad
permanente y la inmutabilidad, la hacen interesante para otros fines, concretamente
como canal encubierto y con fines maliciosos.
Por una parte, aún no se ha caracterizado el uso de la blockchain por parte
de malwares. Por ello, esta tesis también analiza el actual estado del arte en este
ámbito. Una de las lecciones aprendidas al analizar los datos es que las comunicaciones
encubiertas han recibido poca atención.
Por otro lado, aunque trabajos anteriores han analizado la viabilidad de los
canales encubiertos en una tecnología blockchain concreta llamada Bitcoin, ningún
trabajo anterior ha explorado el uso de Ethereum para establecer un canal encubierto
considerando todos los campos de transacción y contratos inteligentes.
Con el objetivo de fomentar una mayor investigación orientada a la defensa,
en esta tesis se presentan dos mecanismos novedosos. En primer lugar, Zephyrus
aprovecha todos los campos de Ethereum y el bytecode de los contratos inteligentes.
En segundo lugar, Smart-Zephyrus complementa Zephyrus aprovechando los contratos inteligentes escritos en Solidity. Se evalúa, también, la viabilidad y el coste
de ambos mecanismos. Los resultados muestran que Zephyrus, en el mejor de los
casos, puede ocultar 40 Kbits en 0,57 s. por 1,64 US$, y recuperarlos en 2,8 s.
Smart-Zephyrus, por su parte, es capaz de ocultar un secreto de 4 Kb en 41 s. Si
bien es cierto que es caro (alrededor de 1,82 dólares por bit), el sigilo proporcionado
podría valer la pena para los atacantes. Además, estos dos mecanismos pueden
combinarse para aumentar la capacidad y reducir los costesPrograma de Doctorado en Ciencia y Tecnología Informática por la Universidad Carlos III de MadridPresidente: José Manuel Estévez Tapiador.- Secretario: Jorge Blasco Alís.- Vocal: Luis Hernández Encina
Proof of Assets in the Diem Blockchain
A great challenge for distributed payment systems is their compliance with regulations, such as anti-money laundering, insolvency legislation, countering the financing of terrorism and sanctions laws. After Bitcoin\u27s MtGox scandal, one of the most needed auditing functionalities for financial solvency and tax reporting purposes is to prove ownership of blockchain reserves, a process known as Proof of Assets (PoA). This work formalizes the PoA requirements in account-based blockchains, focusing on the unique hierarchical account structure of the Diem blockchain, formerly known as Libra. In particular, we take into account some unique features of the Diem infrastructure to consider different PoA modes by exploring time-stamping edge cases, cold wallets, locked assets, spending ability delegation and account pruning, among the others. We also propose practical optimizations to the byte-size of PoA in the presence of light clients who cannot run a full node, including skipping Validator updates, while still maintaining the 66.7% Byzantine fault tolerance (BFT) guarantee
Mind the Gap: Trade-Offs between Distributed Ledger Technology Characteristics
When developing peer-to-peer applications on Distributed Ledger Technology
(DLT), a crucial decision is the selection of a suitable DLT design (e.g.,
Ethereum) because it is hard to change the underlying DLT design post hoc. To
facilitate the selection of suitable DLT designs, we review DLT characteristics
and identify trade-offs between them. Furthermore, we assess how DLT designs
account for these trade-offs and we develop archetypes for DLT designs that
cater to specific quality requirements. The main purpose of our article is to
introduce scientific and practical audiences to the intricacies of DLT designs
and to support development of viable applications on DLT
SGXonerated: Finding (and Partially Fixing) Privacy Flaws in TEE-based Smart Contract Platforms Without Breaking the TEE
TEE-based smart contracts are an emerging blockchain architecture,
offering fully programmable privacy with better performance than alternatives like secure multiparty computation. They can also support compatibility with existing smart contract languages, such that existing (plaintext) applications can be readily ported, picking up privacy enhancements automatically. While previous analysis of TEE-based smart contracts have focused on failures of TEE itself, we asked whether other aspects might be understudied. We focused on state consistency, a concern area highlighted by Li et al., as well as new concerns including access pattern leakage and software upgrade mechanisms. We carried out a code review of a cohort of four TEE-based smart contract platforms. These include Secret Network, the first to market with in-use applications, as well as Oasis, Phala, and Obscuro, which have at least released public test networks.
The first and most broadly applicable result is that access pattern leakage occurs when handling persistent contract storage. On Secret Network, its fine-grained access pattern is catastrophic for the transaction privacy of SNIP-20 tokens. If ERC-20 tokens were naively ported to Oasis they would be similarly vulnerable; the others in the cohort leak coarse-grained information at approximately the page level (4 kilobytes). Improving and characterizing this will require adopting techniques from ORAMs or encrypted databases. Second, the importance of state consistency has been underappreciated, in part because exploiting such vulnerabilities is thought to be impractical. We show they are fully practical by building a proof-of-concept tool that breaks all advertised privacy properties of SNIP-20 tokens, able to query the balance of individual accounts and the token amount of each transfer. We additionally demonstrate MEV attacks against the Sienna Swap application. As a final consequence of lacking state consistency, the developers have inadvertently introduced a decryption backdoor through their software upgrade process. We have helped the Secret developers mitigate this through a coordinated vulnerability disclosure, after which their transaction replay defense is roughly on par with the rest
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