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Oracles

A blockchain oracle serves as a crucial link between on-chain systems, such as smart contracts, and off-chain data providers. By sourcing, verifying, and transmitting off-chain data to the blockchain, an oracle expands the capabilities of smart contracts, which otherwise would have limited access to on-chain data alone. Oracles enable smart contracts to leverage trusted external data to execute their functions.

It's important to note that a blockchain oracle is not the direct source of data but rather the system responsible for querying, confirming, and authenticating off-chain data sources. It then relays this information to the blockchain network. The transmitted data can include asset prices, natural disaster updates, statistics, political events, geolocation data, and more.

Typically, a blockchain oracle consists of a smart contract operating on the blockchain and an off-chain component known as the oracle. The smart contract receives data requests from other on-chain applications and relays them to the oracle. The oracle node queries data sources through APIs, retrieves the relevant information, and stores it on the blockchain.

Blockchain oracles play a critical role in enabling the execution of agreements through smart contracts. While smart contracts are self-governing programs operating on the blockchain, their ability to interact with deterministic off-chain systems poses complexity. Deterministic systems produce expected results based on specific inputs and static states. Blockchains aim for consensus on basic binary questions relying on data already stored in their ledgers. However, incorporating off-chain data directly into blockchains would disrupt determinism, as off-chain data is subject to frequent changes. This would hinder consensus among nodes and undermine the distributed nature of blockchain.

Oracles solve this problem by pulling external data and relaying it to blockchains for use in smart contracts. By doing so, they allow blockchains to securely utilize off-chain data without compromising consensus. Nonetheless, the use of oracles introduces challenges, including the potential for incorrect or manipulated data inputs. Centralized oracles can act as single points of failure and raise trust concerns. To address these issues, multiple oracles can be used to provide redundant data, and decentralized oracles offer tamper-proof and transparent data sourcing through distributed networks of nodes.

There are two broad categories of oracles: centralized and decentralized. Centralized oracles serve as single sources of truth, controlled by a single entity, and provide data to smart contracts. They offer faster data retrieval and greater control but face drawbacks such as single points of failure and lack of transparency. Decentralized oracles, on the other hand, leverage networks of nodes to securely access and validate external data. They offer advantages like no single point of failure, transparency, and censorship resistance. However, they can be more complex to set up and may have scalability limitations.

Chainlink is a chain-agnostic and API-agnostic decentralized oracle network initially built on Ethereum. Chainlink’ss designed to connect off-chain data sources, such as financial market data to on-chain smart contracts. “Oracles'' can be thought of as the bridge on which on-chain smart contracts access, retrieve, and verify data coming from outside of a blockchain. They also relay data and instructions from smart contracts to other off-chain systems. 

For example, the Ethereum network is only aware of the transactions, blocks, and ether that live within its closed Ethereum Virtual Machine (EVM). It has no way of ‘knowing’ the current price of oil, who won the Yankees game, or if the stock market dropped 5% this week. However, for Ethereum (or any blockchain) to disrupt traditional finance and provide greater value to its users, it will need a way to incorporate these kinds of data in a trustless, decentralized way. The ideal oracle should provide perfect accuracy, be manipulation-resistant, and be sufficiently decentralized from a security standpoint. 

The challenge of getting off-chain information on-chain in a reliable, trust-minimized manner is generally known as the "oracle problem" and has remained largely unsolved since the creation of Bitcoin. Using information sourced outside the native blockchain introduces new potential attack vectors--i.e., how accurate is this data? If the data provided to the smart contract could ultimately be used to exploit the system for millions of dollars, then an attacker has the incentive of up to millions of dollars to manipulate that data. Because of this, the oracle network must be designed to reduce the impact of bad actor(s), reduce their incentive to provide inaccurate data, and minimize trust around one data point. 

Many early attempts to solve this issue resulted in semi-trusted multi-signature schemes that just moved the points of trust (e.g., potential points of failure or manipulation) to different locations. Aside from being accurate, the oracle network must be resilient and robust enough to not become a single point of failure. The collection of oracles must be decentralized enough in numbers, geography, data sources, hardware/software, etc. (just like Bitcoin ASICs) to make them resistant to corruption, manipulation, and downtime. Decentralization among blockchains and oracle networks remains a spectrum with different use cases requiring different levels of security and decentralization. All attempts to create a fully decentralized system come with trade-offs to speed, costs, convenience, and performance. 

Oracles can, in theory, connect blockchains and their token incentive structures to nearly anything. Creating verifiable, trusted smart contracts tied to real-world identities could penetrate the voting, passport, and medical history industries. Creating access to reliable and accurate real-world data also opens the door for decentralized sports betting, prediction markets, and insurance, representing trillions in combined economic activity. 

Chainlink puts forth its solution to the oracle problem by connecting different blockchains to the off-chain world while providing “reliable tamper-proof inputs and outputs for complex smart contracts on any blockchain.” In addition, Chainlink aims to become the standard for interacting with other off-chain services, such as payment gateways for use cases, including financial data, financial agreements, insurance, and more.

As an oracle, the solution it offers is trustless connectivity to any API endpoint, including off-chain data sources such as web APIs, data and price feeds, bank or retail payment systems, events data, sports data, market data, IoT, or biometric sensors to a blockchain by retrieving and verifying data originating outside the network. These off-chain data sources are important for various financial services, such as collateral-backed loans and the settlement of derivatives prices.

Chainlink’s primary use case is bringing trust-minimized and secure third-party data via its secure middleware solution without interfering with the blockchain’s consensus. Therefore, Chainlink is a highly secure and flexible oracle network interfacing with the legacy world and its real-world data. Chainlink also offers a blockchain abstraction layer for enterprise use which allows enterprises that want to become blockchain-enabled to integrate with Chainlink for access to many blockchain networks with only one integration.