ENCRYPTION OF PROGRAM INSTRUCTIONS IN A NUMERICAL CONTROL DEVICE

In a method for operating a numerical control device for controlling a production machine for producing a workpiece, program instructions generated by CAM software are encrypted with a first encryption key to generate first encrypted program instructions and the first encrypted program instructions are decrypted with a first decryption key to generate first decrypted program instructions. To prevent unauthorized access to the program instructions, the first decrypted program instructions are re-encrypted using a second encryption key to generate second encrypted program instructions, which are stored in a memory of the numerical control device. Subsequently, the second encrypted program instructions are read out of the memory and decrypted record-by-record or block-by-block, such that only those program instructions of the part program which are currently being processed by the numerical control device, or whose processing is imminent and used to control the production machine for the production of the workpiece.