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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-1994
Viacom multimedia and industrial corporation takes control of Paramount Communications for US$ 9.6 billion, as well as Blockbuster Entertainment, a huge video store chain, for US$ 8.4. billion.
1995
Entertainment giant Disney buys Capital Cities-ABC for US$ 19 billion.
The industrial and broadcasting company Westinghouse Corp. buys out CBS for US$ 5.4 billion.
In a US$ 7.2 billion deal, Time Warner acquires Turner Communications, owner of prime cable TV channels CNN, TBS and TNT and a major classic American film library.
1996
Westinghouse/CBS buys Infinity Broadcasting's large group of radio stations.
Murdoch and News Corp. acquire ten more TV stations and TV production studios with the US$ 2.5 billion purchase of New World Communications Group.
Viacom buys half of UPN-TV network, adding that to its other holdings, which include eleven TV stations, along with MTV, VH-1, and other cable TV channels and Paramount movie studios.
1997
Radio Groups Chancellor Media and Evergreen merge and are linked by ownership with Capstar Broadcasting; they also buy ten radio stations from Viacom. By mid-1997 Chancellor/Capstar controls no fewer than 325 radio stations around the United States.
Chancellor/Capstar's controlling ownership group, Hicks Muse Tate & Furst, buys the seventh largest radio group, SFX, adding another seventy-two radio stations, making a total of nearly four hundred stations controlled by this one source.
Westinghouse-CBS buys out American Radio Systems, the fourth largest radio chain in total audience, which gives Westinghouse-CBS over 170 radio stations with a total audience nearly equal to that of the Chancellor/Capstar group.
Giant European-based print and electronic publishing and data base corporations Reed Elsevier and Wolters Kluwer merge.
1998
Bertelsmann buys the Random House-Alfred A. Knopf-Crown Publishing group of book publishers from Newhouse/Advance Publications, adding to its Bantam-Doubleday-Dell publishing group and giving Bertelsmann by far the largest English-language publishing operations.
1999
AOL, the worlds leading Internet service provider and Time Warner, the worlds leading classical media company merge in a US$ 243.3 billion deal.
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It is a system, where letters get converted into numeric characters.
The numbers were not written down and sent but signaled with torches.
for example:
A=1-1
B=1-2
C=1-3
W=5-2
for more information see:
Writing and calculating came into being at about the same time. The first pictographs carved into clay tablets are used for administrative purposes. As an instrument for the administrative bodies of early empires, who began to rely on the collection, storage, processing and transmission of data, the skill of writing was restricted to a few. Being more or less separated tasks, writing and calculating converge in today's computers.
Letters are invented so that we might be able to converse even with the absent, says Saint Augustine. The invention of writing made it possible to transmit and store information. No longer the ear predominates; face-to-face communication becomes more and more obsolete for administration and bureaucracy. Standardization and centralization become the constituents of high culture and vast empires as Sumer and China.