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Key-Systems |
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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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AT&T
AT&T
Corporation provides voice, data and video communications services to
large and small businesses, consumers and government entities. AT&T
and its subsidiaries furnish domestic and international long
distance, regional, local and wireless communications services, cable
television and Internet communications services. AT&T also
provides billing, directory and calling card services to support its
communications business. AT&T's primary lines of business are
business services, consumer services, broadband services and wireless
services. In addition, AT&T's other lines of business include
network management and professional services through AT&T
Solutions and international operations and ventures. In June 2000,
AT&T completed the acquisition of MediaOne Group. With the
addition of MediaOne's 5 million cable subscribers, AT&T becomes
the country's largest cable operator, with about 16 million customers
on the systems it owns and operates, which pass nearly 28 million
American homes. (source: Yahoo)
Slogan:
"It's all within your reach"
Business
indicators:
Sales
1999: $ 62.391 bn (+ 17,2 % from 1998)
Market
capitalization: $ 104 bn
Employees:
107,800
Corporate
website: http://www.att.com
 http://www.att.com/
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