According to examples, an apparatus may include a security enclosure, a main processor housed in the security enclosure, and a physical security monitoring control unit (PSMCU) processor housed in the security enclosure. The PSMCU processor may cause the apparatus to switchably operate between a first mode and a second mode. In the first mode, the PSMCU processor may allow access by the main processor to a first cryptographic key while preventing access by the main processor to a second cryptographic key. In addition, in the second mode, the PSMCU processor may allow access by the main processor to the second cryptographic key while preventing access by the main processor to the first cryptographic key.