The physical security architecture is the implementer’s view of life, the bricks and mortar of your enterprise security architecture. File management systems are a featured sub-system of every operating system. Typical examples are the file management capabilities within the UNIX/Linux operating system family or within the MS Windows 10/11/2022 operating system family. Encryption of data is discussed later in this chapter under Security Mechanisms. One of the ways that encryption can be applied is to encrypt entire files, selected records within a file, selected fields within a database record. The main challenge with using file encryption is how to manage the encryption keys. Entropy is a measure of the randomness contained within the data. The redundancy of data reduces the entropy. Entropy is measured as the number of truly random bits in a unit of data, as opposed to redundant bits. Database management systems are much more sophisticated than file systems, offering much more extensive data management and protection facilities.