Conceptually, if we imagine that we keep all our most valuable data or information in a castle, without any security measures, anyone could enter and take whatever they want. Questions: So$,$ which elements of defense in depth should be applied to obtain an adequate level of protection? List and explain the function of each security element or layer. Is there such a thing as a completely secure medieval or modern $$castle$?$ Include at least $2$ academic sources, formats and must be cited in accordance with current APA regulations.