Distrust between data providers and data consumersis one of the main obstacles hampering digitaldatacommerce to take off. Data providers want toget paid for what they offer, while data consumerswant to know exactly what are they paying for beforeactually paying for it. In this paper, we summarizea protocol that overcomes this obstacle by buildingtrust based on two main ideas. First, a probabilisticverification protocol, where some random samples ofthe real dataset are shown to buyers in order to allowthem to make an assessment before committing anypayment; and second a guaranteed, protected paymentprocess, enforced with smart contracts on a publicblockchain, that guarantees the payment of the data ifand only if the data provided meets the agreed terms,and that refunds honest players otherwise.