Key-Systems As stated, telecommunication is seen as an unreliable media for transporting secret messages. Therefore today, cryptography is needed more than ever before, especially for e-commerce. Key cryptosystems try to provide more privacy. symmetric-key cryptosystems: The same key is used for both encryption and decryption. In this case the encipherer and the recipient of the message/text have to agree on a common key before the enciphering-process can start. And most of all they should trust each other. And exactly this is the main problem of this system: how to exchange the key without offering an opportunity for stealing it? In former times messengers or pigeons were doing the exchange of those keys. Symmetric-key systems make sense in small entities. If a lot of people are spread over a wide area and belong to the same network, distributing the keys starts getting complicated. Today, those cryptosystems get controlled by other keys, based on highly complex mathematical algorithms. some symmetric-key systems are: - DES (Data Encryption Standard), the standard for credit cards - Triple-DES, which is a variation of DES, encrypting the plaintext three times. - IDEA (International Data Encryption Standard) - blowfish encryption algorithm, which is said to be faster than DES and IDEA Security and confidence are the key-words for a popular key-system: As DES and its successors have been used for so many years and by many people without having been broken, they are considered safe - safer than others, not used that frequently, no matter whether they are actually safer or not. For further information see: http://www.sbox.tu-graz.ac.at/home/j/jonny/projects/crypto/symmetr/content.htm

TEXTBLOCK 1/1 // URL: http://world-information.org/wio/infostructure/100437611776/100438659090

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.

INDEXCARD, 1/1