Modular security control device for controlling an apparatus or an installation, comprising: - a basic control apparatus, the basic control apparatus being designed and set up in such a manner that an apparatus or an installation which is connected to the basic control apparatus is controlled by means of the sequence of a control program in the basic control apparatus, and - a security module (200, 300) which is designed and set up to provide or perform a cryptographic functionality for the basic control apparatus, - the security module (200, 300) being able to be connected to the basic control apparatus by means of a data connection via a data interface, - the basic control apparatus being designed and set up to interact with the security module (200, 300) in order to achieve a security function of the security control device if the security module is connected to the basic control apparatus, and - the basic control apparatus being designed and set up to query an identity and/or authenticity of the security module (200, 300) if the security module is connected to the basic control apparatus, furthermore - the basic control apparatus comprising a detection device which is designed and set up in such a manner that the detection device can be used to determine whether or not a security module (200, 300) is connected to the basic control apparatus via the data interface, and - the basic control apparatus being designed and set up in such a manner that a separate basic apparatus crypto functionality provided in the basic control apparatus is used instead of a cryptographic functionality of a security module (200, 300) if the detection device does not detect a security module (200, 300) connected via the data interface. - a basic control apparatus, the basic control apparatus being designed and set up in such a manner that an apparatus or an installation which is connected to the basic control apparatus is controlled by means of the sequence of a control program in the basic control apparatus, and - a security module (200, 300) which is designed and set up to provide or perform a cryptographic functionality for the basic control apparatus, - the security module (200, 300) being able to be connected to the basic control apparatus by means of a data connection via a data interface, - the basic control apparatus being designed and set up to interact with the security module (200, 300) in order to achieve a security function of the security control device if the security module is connected to the basic control apparatus, and - the basic control apparatus being designed and set up to query an identity and/or authenticity of the security module (200, 300) if the security module is connected to the basic control apparatus, furthermore - the basic control apparatus comprising a detection device which is designed and set up in such a manner that the detection device can be used to determine whether or not a security module (200, 300) is connected to the basic control apparatus via the data interface, and - the basic control apparatus being designed and set up in such a manner that a separate basic apparatus crypto functionality provided in the basic control apparatus is used instead of a cryptographic functionality of a security module (200, 300) if the detection device does not detect a security module (200, 300) connected via the data interface.