Deliverable D5.1 documents the first releases of the ENTRUST Blockchain Architecture, Authorization and Secure On- and Off-Chain Data Management. D5.1 thoroughly analyses ENTRUST’s Blockchain Architecture and the Tracer enabling the secure management of CMDs in the ENTRUST Framework. More specifically, D5.1 presents the landscape of Blockchain types and platforms and their use in the medical domain towards selecting the most suitable Blockchain network. Then, it defines the requirements for the ENTRUST Blockchain and Tracer and provides the ENTRUST Blockchain Architecture along with the definition of smart contracts that will facilitate the storage and retrieval of sensitive medical device data towards establishing the trustworthiness of CMDs. The functionalities of the Tracer that enable the tracing operations in high- and low-end medical devices are also specified. Finally, D5.1 defines the research plan for the development of functionalities for the second releases of the ENTRUST Blockchain and the Tracer.