An apparatus, a method and a product for transferring security-critical medical data records via a public network are disclosed. In order to be able to transmit security-critical data sections in pseudonymized form, a pseudonymization function is adaptively applied to the data records. The pseudonymization function is in each case calculated dynamically on the basis of a processing context that has been read in and that takes account of the planned user role, the planned intended use of the data processing and an application context.