Human society is transitioning to a knowledge economy. The rise of Artificial Intelligence has once more shown that the value of data grows dramatically as they are shared and aggregated.However, from established applications like Finance, which require selective handling of confidential information, to the AI revolution - the same issue persists: we share data with centralized entities with no guarantees on the exact handling of our data. We propose a system (Palliora) based on a public blockchain in which everyone can selectively share their data for trusted, confidential and verifiable computation, knowing that only the intended recipients will have access. Moreover, such a system guarantees fairness to all participants in an AI ecosystem: data providers, model providers, training providers, model users, which is essential for an unplugged growth of AI technology. We achieve our goals by introducing in Palliora both several independent actors, that populate overlapping networks, and a peculiar contract standardization. Among our actors we have DA nodes, which take care of Data Availability, Guardians, which take care of a decentralized access-control system, Calculators, which perform outsourced computations (with varying confidentiality levels), and Verifiers, which check the quality and consistency of input and output data. Palliora’s contracts permit free negotiations among all users and all actors, while enforcing correct execution and fair distribution of rewards.