The invention relates to a method for changing safety-relevant data for a control device for detecting changed data in a data processing system. In this case, the data which have been changed are encrypted using an individualized key. In addition, the following method steps are predefined: a first checksum is formed using the encrypted data, the encrypted data, the key and the first checksum are stored in at least one data record in the data processing system, the encrypted data are read from a memory of the data processing system, the data are decrypted and the decrypted data are displayed, the data which have been changed are checked for identity with the decrypted data and a second checksum is formed and is stored in the at least one data record. In addition, the invention relates to a system for carrying out the method according to the invention.