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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150
A
The Roman smoke signals network consisted of towers within a 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
About 750
In Japan block printing is used for the first time.
868
In China the world's first dated book, the Diamond Sutra, is printed.
1041-1048
In China moveable types made from clay are invented.
1088
The first of the great medieval universities was established in Bologna. At the beginning universities predominantly offered a kind of do-it-yourself publishing service.
Books still had to be copied by hand and were so rare that a copy of a widely desired book qualified for being invited to a university. Holding a lecture equaled to reading a book aloud, like a priest read from the Bible during services. Attending a lecture equaled to copy a lecture word by word, so that you had your own copy of a book, thus enabling you to hold a lecture, too.
For further details see History of the Idea of a University,
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Founded in 1929 Disney primarily engages in child and adult entertainment. Starting with the production of animated motion-picture cartoons in the late 1940s Disney began to make also nature documentaries and live-action motion pictures, as well as short cartoons and live-action programs for television. In 1955 the company opened Disneyland, which was their first amusement park. Further openings of amusement parks in the U.S. and Europe followed. In 1996 Disney acquired Capital Cities/ABC Inc., which owned the ABC television network.
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The Internet Software Consortium (ISC) is a nonprofit corporation dedicated to the production of high-quality reference implementations of Internet standards that meet production standards. Its goal is to ensure that those reference implementations are properly supported and made freely available to the Internet community.
http://www.isc.org
Communications satellites are relay stations for radio signals and provide reliable and distance-independent high-speed connections even at remote locations without high-bandwidth infrastructure.
On point-to-point transmission, the transmission method originally employed on, satellites face increasing competition from
In the future, satellites will become stronger, cheaper and their orbits will be lower; their services might become as common as satellite TV is today.
For more information about satellites, see How Satellites Work (
The Clipper Chip is a cryptographic device proposed by the U.S. government that purportedly intended to protect private communications while at the same time permitting government agents to obtain the "keys" upon presentation of what has been vaguely characterized as "legal authorization." The "keys" are held by two government "escrow agents" and would enable the government to access the encrypted private communication. While Clipper would be used to encrypt voice transmissions, a similar chip known as Capstone
would be used to encrypt data. The underlying cryptographic algorithm, known as Skipjack, was developed by the National Security Agency (NSA).
Bruce Schneier is president of Counterpane Systems in Minneapolis. This consulting enterprise specialized in cryptography and computer security. He is the author of the book Applied Cryptography and inventor of the Blowfish and Twofish encryption algorithms.