• blockchain
• Chainlink
• decentralized
• DIABOLIK
• oracle
• oracle problem
• smart contracts

The blockchain is one of the most popular and discussed technologies to date, considered by many to be the greatest invention since the Internet. The first successful blockchain was that of Bitcoin, which allows the exchange of the Bitcoin cryptocurrencies in an anonymous, secure, and decentralized way. Successively to Bitcoin, the Ethereum blockchain was born in 2015, which allows not only the exchange of cryptocurrencies but also the development of decentralized applications, called smart contracts, that enjoy the benefits of blockchain. However, since the blockchain is a closed system, smart contracts cannot access classic data sources such as databases or web APIs. This is an important limitation for data-dependent applications. To overcome this problem, the concept of Oracle was introduced. The Oracle is an entity external to the blockchain that provides data from off-chain data sources to on-chain smart contracts. However, oracles introduce a novel issue, namely the Oracle Problem. The Oracle Problem refers to the fact that although the blockchain is a secure technology, if the oracles providing data to it were to be unreliable, the entire system would become untrustworthy. This thesis investigates the Oracle Problem with the main technologies that address it and introduces DIABOLIK. DIABOLIK is a new decentralized oracle architecture we propose that aims to provide smart contracts with on-demand data in a secure and reliable manner.