The 19th Century: Machine-Assisted Manufacturing Eli Whitney's proposal for a simplification and standardization of component parts marked a further milestone in the advance of the automation of work processes. In 1797 he suggested the manufacture of muskets with completely interchangeable parts. As opposed to the older method under which each gun was the individual product of a highly skilled gunsmith and each part hand-fitted, his method permitted large production runs of parts that were readily fitted to other parts without adjustment and could relatively easy be performed by machines. By the middle of the 19th century the general concepts of division of labor, assembly of standardized parts and machine-assisted manufacture were well established. On both sides of the Atlantic large factories were in operation, which used specialized machines to improve costs, quality and quantity of their products.

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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

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water-clocks The water-clocks are an early long-distance-communication-system. Every communicating party had exactly the same jar, with a same-size-hole that was closed and the same amount of water in it. In the jar was a stick with different messages written on. When one party wanted to tell something to the other it made a fire-sign. When the other answered, both of them opened the hole at the same time. And with the help of another fire-sign closed it again at the same time, too. In the end the water covered the stick until the point of the wanted message.

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Hieroglyphs Hieroglyphs are pictures, used for writing in ancient Egypt. First of all those pictures were used for the names of kings, later more and more signs were added, until a number of 750 pictures

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