1. An apparatus to transfer medical security-critical data records from a transmission station to at least one receiver station via a digital network, the apparatus comprising: an input data interface configured to capture a medical security-critical data record to be transferred; a context capture unit configured to capture a planned processing context for the medical security-critical data record; a processor including a rulebook machine, the rulebook machine configured to store a multiplicity of variable rules for dynamically calculating pseudonymization functions, the rulebook machine further configured to be dynamically updated based on the captured planned processing context during operation of the apparatus; wherein the processor is configured to execute computer-readable instructions to calculate a pseudonymization function based on the multiplicity of variable rules, apply the pseudonymization function to sections of the medical security-critical data record that are determined as critical to security, and produce a pseudonymized data record for transfer to the at least one receiver station; and wherein the captured planned processing context is indicative of a planned processing of the pseudonymized data record.