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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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Technological measures
As laid down in the proposed EU Directive on copyright and related  rights in the information society technological measures mean "... any technology, device, or component that, in the normal course of its operations, is designed to prevent or inhibit the infringement of any copyright..." The U.S. DMCA (Digital Millennium Copyright Act) divides technological measures in two categories: 1) measures that prevent unauthorized access to a copyrighted work, and 2) measures that prevent unauthorized copying of a copyrighted work. Also the making or selling of devices or services that can be used to circumvent either category of technological measures is prohibited under certain circumstances in the DMCA. Furthermore the 1996 WIPO Copyright Treaty states that the "... contracting parties shall provide adequate legal protection and effective legal remedies against the circumvention of effective technological measures that are used by authors..."
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