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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17th century Cardinal Richelieu invents an encryption-tool called grille, a card with holes for writing messages on paper into the holes of those cards. Afterwards he removes the cards and fills in the blanks, so the message looks like an ordinary letter. The recipient needs to own the same card
- Bishop John Wilkins invents a cryptologic system looking like music notes. In a book he describes several forms of steganographic systems like secrets inks, but also the string cipher. He mentions the so-called Pig Latin, a spoken way of encryption that was already used by the ancient Indians
- the English scientist, magician and astrologer
1605/1623 Sir Francis Bacon (= Francis Tudor = William Shakespeare?) writes several works containing ideas about cryptography. One of his most important advises is to use ciphers in such a way that no-one gets suspicious that the text could be enciphered. For this the steganogram was the best method, very often used in poems. The attempt to decipher Shakespeare's sonnets (in the 20th century) lead to the idea that his works had been written by Francis Bacon originally.
1671 Leibniz invents a calculating machine that uses the binary scale which we still use today, more advanced of course, called the ASCII code
18th century this is the time of the Black Chambers of espionage in Europe, Vienna having one of the most effective ones, called the "Geheime Kabinettskanzlei", headed by Baron Ignaz von Koch. Its task is to read through international diplomatic mail, copy letters and return them to the post-office the same morning. Supposedly about 100 letters are dealt with each day.
1790's Thomas Jefferson and Robert Patterson invent a wheel cipher
1799 the Rosetta Stone is found and makes it possible to decipher the Egyptian Hieroglyphs
1832 or 1838 Sam Morse develops the Morse Code, which actually is no code but an enciphered alphabet of short and long sounds. The first Morse code-message is sent by telegraph in 1844.
1834 the
1844 the invention of the telegraph changes cryptography very much, as codes are absolutely necessary by then
1854 the Playfair cipher is invented by Sir Charles Wheatstone
1859 for the first time a tomographic cipher gets described
1861 Friedrich W. Kasiski does a cryptoanalysis of the Vigenère ciphers, which had been supposed to be uncrackable for ages
1891 Major Etienne Bazeries creates a new version of the wheel cipher, which is rejected by the French Army
1895 the invention of the radio changes cryptography-tasks again and makes them even more important
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