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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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ARPAnet
ARPAnet was the small network of individual computers connected by leased lines that marked the beginning of today's global data networks. Being an experimental network mainly serving the purpose to test the feasibility of  wide area networks, the possibility of remote computing, it was created for resource sharing between research institutions, not for messaging services like E-mail. Although research was sponsored by US military, ARPAnet was not designed for directly martial use but to support military-related research.
In 1969 ARPANET went online and links the first two computers, one of them located at the University of California, Los Angeles, the other at the Stanford Research Institute.
But ARPAnet has not become widely accepted before it was demonstrated in action to a public of computer experts at the First International Conference on Computers and Communication in Washington, D. C. in 1972.
Before it was decommissioned in 1990, NSFnet, a network of scientific and academic computers funded by the National Science Foundation, and a separate new military network went online in 1986. In 1988 the first private Internet service providers offered a general public access to NSFnet. Beginning in 1995, after having become the backbone of the Internet in the USA, NSFnet was turned over to a consortium of commercial backbone providers. This and the launch of the World Wide Web added to the success of the global data network we call the Net.
In the USA commercial users already outnumbered military and academic users in 1994.
Despite the rapid growth of the Net, most computers linked to it are still located in the United States.
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