Abstract: A chip card is protected against copying by having a data memory for storage of data that are protected, at least in a sub-region of the data memory, against alteration by users or attackers outside of a privileged group. Members of this group can write an individual identifier for this chip card into this protected memory region once, and can write a digital signature of this identifier to an arbitrary memory region of the data memory. The digital signature can be generated with the use of a secret key for which an associated public key exists with which it can be checked whether the digital signature was generated from the individual identifier with the use of a secret key.