A method of protecting a microcomputer system against manipulation of data
stored in a storage assembly of the microcomputer system, particularly
for protecting a program stored in the storage assembly, is described. In
the method, the data is stored in marked or encrypted form in the storage
assembly with the aid of an asymmetrical encryption method. In order to
minimize the misuse of private keys which fall into the hands of
unauthorized persons, a smart card protected by a personal identification
number, on which the private key and an encryption algorithm for the
asymmetrical encryption method are stored, is used for marking or
encrypting the data.