# The Blockchain Oracle Problem in Decentralized Finance--A Multivocal Approach
## 6 Discussion
Of course, Chainlink is one of the first oracle providers; however, focusing and querying only a precise oracle service can also lead to a problem of centralization. From the Chainlink whitepaper, we also find out that they are willing to make a sort of certification of oracles that distinguish between reliable and unreliable sources [6; 129]. If, on the one hand, this can help platforms in selecting reliable oracles, this can also create an oligarchy circle in which new providers are prevented from playing. Another aspect to consider is the transparency of oracle choice. Unless the client does appropriate research, it is not always transparent the oracle service that is used in the DeFi ecosystem. A recent AMM project, named \"SushiSwap\", added in its trading interface information about the oracle that communicates the price for every trading pairs. However, when Chainlink is declared as an oracle, it does still leave with some doubts. If, on the one hand, it means that the platform relies on a third-party oracle, it does not explain the type of contract that has been made with that provider. As an oracle marketplace, Chainlink, depending on the agreed price, may query more or less trusted oracle or update the price more or less frequently [6]. In the DeFi sector, the oracle problem can also lead to the condition in which the unreliability of the oracle and the data source could determine an unfair risk allocation. That oracles can be imprecise, slow, and may undergo temporary malfunction should be a pretty known condition by the company as well as traders [51]. However, if insiders can influence the work of oracles or be aware of their data before others, they may obtain an unjust revenue [18; 111]. As in the case of Terra Money, the early oracle data were exploited to perform a front-running attack [104]. The bZx case and many of the flash-loan attacks instead were sometimes not due to a malfunction but to knowledge about the price oracle's poor design [122]. This creates then a paradox of transparency. It is true that oracles have to be transparent to be trusted, but if their functioning is completely exposed, it can be easily exploited by malevolent actors. The governance of oracles also raises concerns. In fact, although the chance of a Sybil attack on MakerDAO was widely explained in academic papers and blog articles [107; 109], this vulnerability was exploited anyway, posing severe doubts on the security and feasibility of decentralized governance [63; 110]. Razor and UMA proposed and employed an economic incentive to counterbalance the possibility of 51% attacks. As written in the UMA whitepaper, \"any on-chain oracle can be corrupted--for a price. Because there is no \"rule of law\" on blockchains outside of economic incentives\" [101]. Therefore, it is arguable that it is possible to prevent oracle corruption with the right economic incentive [34]. From a technical point of view, it is evident that a mechanism to identify faulty oracles quickly and the availability of multiple data sources would increase the reliability of DeFi platforms. Moreover, the DeFi platforms should provide a detailed explanation of the oracle service selection process and trusted data sources. Again, widely accepted selection criteria may help to set the timeliness of oracles in a way that is optimal to prevent attacks, such as front running (too delayed) and flash loans (too precise). Table 5 reorganizes and summarizes the main issues of using oracles in DeFi.