Uma abordagem descentralizada, pública, anônima e tolerante a transações não verificáveis para o dilema dos compradores e vendedores

Abstract

In 2008, Bitcoin, the world’s first fully decentralized currency, brought with it a technological context with broad potential for application in practically all areas. Years later, although explored in several applications, these decentralized technologies still represent a small portion of the online market. Preliminary results of this Thesis point to the difficulty in virtualizing real-world material events in a decentralized way as one of the main obstacles to the decentralization paradigm. Such virtualization, in this Thesis, was restricted to the problem of Non-Verifiable Transactions, such as a cash payment, the provision of a craft service or practically everything that is negotiated in a street market. Now consider an online transaction as a value exchange protocol in which an active party (buyer) pays in advance for goods or services. At this point, there is a risk that the passive party (seller) will act dishonestly and never deliver the goods or services paid for. This risk is called the Buyer’s and Seller’s Dilemma and is particularly challenging in environments involving unverifiable transactions, such as decentralized markets. This can be explained using Game Theory, where rational players tend to choose the equilibrium strategy, which in this case consists of avoiding the transaction in order to avoid losses due to the dishonesty of the other party due to the non-collaborative nature of the game, leading to suboptimal results. The difference between the ideal result and the result obtained in a non-collaborative game is known as the price of anarchy. The lack of collaborative behavior results in problems such as the Buyer’s and Seller’s Dilemma, but also others such as the Public Good Problem, where any good capable of benefiting the entire population equally is neglected by players who only strive for their own achievements, in some cases even sabotaging the public good. The dishonesty of the passive party produces incomplete transactions that cause multibillion-dollar losses annually, even considering only e-commerce. Centralized marketplaces circumvent this problem by using a centralized mediator, such as payment gateways such as Mercado Pago, used by Mercado Livre. However, every centralized process is subject to flaws that favor this central authority and its interests. However, increasingly attentive users are suspicious of the process of paying for and receiving products and services over the Internet, even when mediated by centralized services, whether due to reports of negative vi experiences from other users or even their own. It is therefore interesting to implement solutions that encourage honesty in these scenarios. To this end, this thesis conducted a literature review in search of decentralized solutions capable of encouraging honesty in unverifiable transactions. Based on criteria of decentralization, non-authentication and tolerance to unverifiable transactions, the solutions found were classified, analyzed and compared through three distinct experiments. The first one compared such solutions based on real-world transaction data extracted from the OpenBazzar platform. The second used Agent-Based Simulation to analyze such solutions in real time. The third and final experiment, called Hash Society, proposes a new transaction model designed to stimulate cooperation between agents. This model was also evaluated by Agent-Based Simulation and compared to other solutions. The three experiments carried out bring contributions to the area of decentralized online markets, with new insights and solutions to the dilemma of buyers and sellers.