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:
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Media as today's main information sources unarguably have the power to influence political agenda-setting and public opinion. They decide which topics and issues are covered and how they are reported. Still, in many cases those decisions are not primarily determined by journalistic criteria, but affected by external factors. The importance of shareholders forces media to generate more profit every quarter, which can chiefly be raised by enlarging audiences and hence attracting more advertising money. Therefore the focus of media's programming in many cases shifts towards audience alluring content like entertainment, talk-shows, music and sports.
Further pressure regarding the selection of content occurs from advertisers and marketers, who often implicitly or explicitly suggest to refrain from programming which could show them or their products and services (e.g. tobacco) in an unfavorable light. Interlocking directorships and outright ownerships can moreover be responsible for a selective coverage. Financial connections with defense, banking, insurance, gas, oil, and nuclear power, repeatedly lead (commercial) media to the withholding of information, which could offend their corporate partners. In totalitarian regimes also pressure from political elites may be a reason for the suppression or alteration of certain facts.
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Realizing that he'd need to lower costs
The use of interchangeable parts meant making the individual pieces of the car the same every time. Therefore the machines had to be improved, but once they were adjusted, they could be operated by a low-skilled laborer. To reduce the time workers spent moving around Ford refined the flow of work in the manner that as one task was finished another began, with minimum time spent in set-up. Furthermore he divided the labor by breaking the assembly of the legendary Model T in 84 distinct steps.
Putting all those findings together in 1913 Ford installed the first moving
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A mark (trademark or service mark) is "... a sign, or a combination of signs, capable of distinguishing the goods or services of one undertaking from those of other undertakings. The sign may particularly consist of one or more distinctive words, letters, numbers, drawings or pictures, emblems, colors or combinations of colors, or may be three-dimensional..." (
The Enigma Encryption Machine was famous for its insecurities as for the security that it gave to German ciphers. It was broken, first by the Poles in the 1930s, then by the British in World War II.
The Roman smoke signals network consisted of towers within visible range of each other and had a total length of about 4500 kilometers. It was used for military signaling.
For a similar telegraph network in ancient Greece see
According to the
Claude Chappe built a fixed optical network between Paris and Lille. Covering a distance of about 240kms, it consisted of fifteen towers with semaphores.
Because this communication system was destined to practical military use, the transmitted messages were encoded. The messages were kept such secretly, even those who transmit them from tower to tower did not capture their meaning, they just transmitted codes they did not understand. Depending on weather conditions, messages could be sent at a speed of 2880 kms/hr at best.
Forerunners of Chappe's optical network are the
For more information on early communication networks see