A computer-implemented method provides a requested medical data record to a receiving entity. The method includes receiving a set of medical data records and receiving or initiating a joint data index and, for each medical data record of the set, applying a plurality of hash functions to a patient identifier corresponding to the medical data record to determine a hash vector, the patient identifier corresponding to the medical data record identifying the patient being subject of the medical data record, and updating the joint data index based on the hash vector. Furthermore, it includes providing the joint data index to the receiving entity and receiving a request for a record, corresponding to a request patient identifier and being based on the joint data index, from the receiving entity. The method includes providing the requested medical data record to the receiving entity via a secure communication channel.