Considerações sobre Anonimato, Pseudoanonimato e Criptomoedas

O presente artigo avalia a temática do anonimato e do pseudoanonimato para as criptomoedas. A pergunta de pesquisa avalia se existe, no ordenamento jurídico nacional, algum elemento restritivo para a transação de criptomoedas com o intuito de anonimato. Sob o prisma jurídico, a Lei Geral de Proteção de Dados Pessoais e as normativas da do Banco Central e da Receita Federal integram o quadro de avaliação. Sob o prisma tecnológico, o modo de funcionamento e a relação com anonimato ou pseudoanonimato do Bitcoin, do Monero, do Zcash e do Dash compõem a análise. A conclusão é a de que, até o momento, a transação de criptomoedas verdadeiramente anônimas não encontra vedações expressas na legislação nacional

PRIVACY PRESERVATION FOR TRANSACTION INITIATORS: STRONGER KEY IMAGE RING SIGNATURE AND SMART CONTRACT-BASED FRAMEWORK

Recently, blockchain technology has garnered support. However, an attenuating factor to its global adoption in certain use cases is privacy-preservation owing to its inherent transparency. A widely explored cryptographic option to address this challenge has been ring signature which aside its privacy guarantee must be double spending resistant. In this paper, we identify and prove a catastrophic flaw for double-spending attack in a Lightweight Ring Signature scheme and proceed to construct a new, fortified commitment scheme using the signer’s entire private key. Subsequently, we compute a stronger key image to yield a double-spending-resistant signature scheme solidly backed by formal proof. Inherent in our solution is a novel, zero-knowledge-based, secured and cost-effective smart contract for public key aggregation. We test our solution on a private blockchain as well as Kovan testnet along with performance analysis attesting to efficiency and usability and make the code publicly available on GitHub

The Complex Community Structure of the Bitcoin Address Correspondence Network

Bitcoin is built on a blockchain, an immutable decentralized ledger that allows entities (users) to exchange Bitcoins in a pseudonymous manner. Bitcoins are associated with alpha-numeric addresses and are transferred via transactions. Each transaction is composed of a set of input addresses (associated with unspent outputs received from previous transactions) and a set of output addresses (to which Bitcoins are transferred). Despite Bitcoin was designed with anonymity in mind, different heuristic approaches exist to detect which addresses in a specific transaction belong to the same entity. By applying these heuristics, we build an Address Correspondence Network: in this representation, addresses are nodes are connected with edges if at least one heuristic detects them as belonging to the same entity. In this paper, we analyze for the first time the Address Correspondence Network and show it is characterized by a complex topology, signaled by a broad, skewed degree distribution and a power-law component size distribution. Using a large-scale dataset of addresses for which the controlling entities are known, we show that a combination of external data coupled with standard community detection algorithms can reliably identify entities. The complex nature of the Address Correspondence Network reveals that usage patterns of individual entities create statistical regularities; and that these regularities can be leveraged to more accurately identify entities and gain a deeper understanding of the Bitcoin economy as a whole

Tracking the coffee: from production to the cup with Blockchain and IoT

L'objectiu d'aquest projecte és el disseny i implementació d'un prototip del seguiment de la cadena de subministrament del cafè utilitzant Blockchain i Internet of Things per poder oferir al client final tota la informació de cada un dels passos de la línia de producció, des del començament fins a la tassa de cafè. El client hauria de tenir la certesa que el cafè és d'alta qualitat i que prové del camp, de l'agricultor i el país que el distribuïdor li diu. És un projecte fet a l'empresa thethings.iO i vehiculat també amb el projecte europeu EPIC.The goal of this project is the design and implementation of a prototype of tracking the coffee supply chain using Blockchain and Internet of Things in order to provide to the final client the information of each step of the production line, starting from the very beginning until the cup of espresso is on the table, ready to be tasted. The client should have the certainty that the coffee is a high quality coffee which comes from the field, from the manufacturer and from the country that the distributor says. The project is developed at thethings.iO company and it is also done through the European EPIC project

Behind the chain of obscurity : methodologies for cryptocurrency forensic analysis

Bitcoin and alternative cryptocurrencies are decentralised digital currencies that allow users to anonymously exchange money without requiring the presence of a trusted third party. The privacy components of cryptocurrency can facilitate illegal activities and present new challenges for cybercrime forensic analysis. Tackling such challenges motivates new research interest in cryptocurrency tracking. This thesis explores and proposes novel methodologies and improvements to existing cryptocurrency tracking and analysis methodologies. Our first contribution explores the most commonly used cryptocurrency tracking methodology named Taint Analysis and investigates a potential improvement to the methodology’s tracking precision with the implementation of address profiling. We also introduce two context-based taint analysis strategies and hypothesise behaviours related to the tracked Bitcoins context to create a set of evaluation metrics. We conducted an experiment using sample data from known illegal Bitcoin cases to illustrate and evaluate the methodology, and the results reveal distinct transaction behaviours in tracking between the results with and without address profiling for all of the metrics. Our second contribution proposes a cryptocurrency tracking methodology named Address Taint Analysis that is capable of tracking zero-taint coins created by Privacy-Enhancing Technologies (PETs) called centralised mixer services, which are untrackable with taint analysis tracking. Our results indicate that our proposed address taint analysis can trace the zero-taint Bitcoins from nine well-known mixer services back to the original Bitcoins. Our third contribution investigates and proposes a detection method for Wasabi Wallet’s CoinJoin transactions, which is one of the most recent well-known PET services. Our fourth contribution introduces an open-source library for cryptocurrency tracking and analysis named, TaintedTX , that we utilised to perform our research experiments. The library supports a variety of taint analysis strategies that users can select to track targeted transactions or addresses. The library also includes a compilation of utility functions for address clustering, website scraping, transaction and address classifications