Timeline Cryptography - Introduction Besides oral conversations and written language many other ways of information-transport are known: like the bush telegraph, drums, smoke signals etc. Those methods are not cryptography, still they need en- and decoding, which means that the history of language, the history of communication and the history of cryptography are closely connected to each other The timeline gives an insight into the endless fight between enciphering and deciphering. The reasons for them can be found in public and private issues at the same time, though mostly connected to military maneuvers and/or political tasks. One of the most important researchers on Cryptography through the centuries is David Kahn; many parts of the following timeline are originating from his work.

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Expert system Expert systems are advanced computer programs that mimic the knowledge and reasoning capabilities of an expert in a particular discipline. Their creators strive to clone the expertise of one or several human specialists to develop a tool that can be used by the layman to solve difficult or ambiguous problems. Expert systems differ from conventional computer programs as they combine facts with rules that state relations between the facts to achieve a crude form of reasoning analogous to artificial intelligence. The three main elements of expert systems are: (1) an interface which allows interaction between the system and the user, (2) a database (also called the knowledge base) which consists of axioms and rules, and (3) the inference engine, a computer program that executes the inference-making process. The disadvantage of rule-based expert systems is that they cannot handle unanticipated events, as every condition that may be encountered must be described by a rule. They also remain limited to narrow problem domains such as troubleshooting malfunctioning equipment or medical image interpretation, but still have the advantage of being much lower in costs compared with paying an expert or a team of specialists.

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