“…Centralized solutions can be often decentralized by multiplying central elements [14-16, 21, 25, 28, 36, 42, 43], and decentralized proposals can be centralized by limiting the number of security control elements to single node [17,38,45,46,50]. Similarly, some of the research we reviewed [26,30,31,34,36,44,49,52,54,56] cannot be categorized in either category. They work equally well for either architecture without modification and can be seen as complementary extensions for complex security solutions, helping with particular issues (e.g., authentication, auditing, context-awareness).…”