Exchange-assisted cloud-based data trading (ECDT) is a promising paradigm in current marketplaces, where an exchange provides underlying trading services while the cloud serves as a fundamental base for data sellers, brokers, and data buyers to enable them to benefit from data trading. However, directly integrating existing commercial cloud services into an exchange system suffers from practicality issues. In existing ECDT systems, the data outsourced to the cloud generally follows an “encrypt-then-outsource” paradigm, and the encrypted database makes it impractical for brokers to generate and deliver on-demand data products to the buyer, thereby hindering subscription-based data trading. In this paper, we propose a secure and efficient data delivery scheme, dubbed ESECDT, for subscription-based ECDT. ESECDT consists of data entrustment and data delivery and supports continuous data entrustment and customized data delivery while freeing the broker from heavy costs in terms of computation and communication. We formally define and prove the security of ESECDT in the random oracle model. We also implement an ESECDT prototype and conduct a comprehensive performance evaluation, which demonstrates the efficiency and practicality of ESECDT.