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:
TEXTBLOCK 1/1 // URL: http://world-information.org/wio/infostructure/100437611776/100438659090
Searching for the Balduinist fluorescenting phosphor (Balduinischer Leuchtphosphor), an artificial fluorescent, Johann Heinrich Schulze realized the first photocopies, but does not put them into practical use.
Not before 1843 the first optical photocopier was patented, when William Henry Fox Talbot got granted a patent for his magnifying apparatus.
In 1847 Frederick Collier Bakewell developed a procedure for telecopying, a forerunner of the fax machine. But not before 1902 images could be transmitted. Almost 200 years after Schulze's discovery, for the first time photo telegraphy was offered as telecommunication service in Germany in 1922.
Source: Klaus Urbons, Copy Art. Kunst und Design mit dem Fotokopierer, Köln: Dumont, 1993 (2nd edition)