Abstract: A blockchain-based, decentralized data marketplace is described. The marketplace allows data sellers to sell their data to data buyers in exchange for payments in tokens. The marketplace allows for securely and anonymously selling data in a trusted environment that is also fair to all participants and provides data sellers with the ability to control and monetize their own data (e.g., personal data). A notary with access to “ground truth” data can validate data that is being offered in the marketplace to ensure that it is not falsified or fabricated before it is purchased by a data buyer. The marketplace implements blockchain-based smart contracts that work together, and with cryptographic protocols, to achieve an efficient, decentralized data marketplace where data sellers and data buyers transact directly with one another while remaining anonymous, if desired.