Method and system for activating an encrypted file

The method involves passing an equipment identifier from a local computer system to a central station, computing a new equipment identifier using a change code, specifying a first enciphered code using a key, specifying a second enciphered code using the data file identifier, passing the enciphered codes to the local system, computing the new equipment identifier, the key and data file identifier in the local system and releasing the data file. The method involves passing an equipment identifier (ID(i-1)) from a local computer system to a central station, computing a new equipment identifier (ID(i)) from the equipment number and a change code, specifying a first enciphered code (PIN) using the computed code and a key (k), specifying a second enciphered code (ACW) using the data file identifier and the key, passing the enciphered codes to the local system, computing the new equipment identifier in the local system from the stored identifier and the change code, computing the key from the first enciphered code and the equipment identifier, computing the data file identifier (AC) from the second enciphered code and the key and releasing the data file for use by the local system. Independent claims are also included for the following: a system for managing and releasing access rights to data files.