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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1913 the wheel cipher gets re-invented as a strip
1917
- an AT&T-employee, Gilbert S. Vernam, invents a polyalphabetic cipher machine that works with random-keys
1918 the Germans start using the ADFGVX-system, that later gets later by the French Georges Painvin
- Arthur Scherbius patents a ciphering machine and tries to sell it to the German Military, but is rejected
1919 Hugo Alexander Koch invents a rotor cipher machine
1921 the Hebern Electric Code, a company producing electro-mechanical cipher machines, is founded
1923 Arthur Scherbius founds an enterprise to construct and finally sell his
late 1920's/30's more and more it is criminals who use cryptology for their purposes (e.g. for smuggling). Elizabeth Smith Friedman deciphers the codes of rum-smugglers during prohibition regularly
1929 Lester S. Hill publishes his book Cryptography in an Algebraic Alphabet, which contains enciphered parts
1933-1945 the Germans make the Enigma machine its cryptographic main-tool, which is broken by the Poles Marian Rejewski, Gordon Welchman and Alan Turing's team at Bletchley Park in England in 1939
1937 the Japanese invent their so called Purple machine with the help of Herbert O. Yardley. The machine works with telephone stepping relays. It is broken by a team of
1930's the Sigaba machine is invented in the USA, either by W.F. Friedman or his colleague Frank Rowlett
- at the same time the British develop the Typex machine, similar to the German Enigma machine
1943 Colossus, a code breaking computer is put into action at Bletchley Park
1943-1980 the cryptographic Venona Project, done by the NSA, is taking place for a longer period than any other program of that type
1948 Shannon, one of the first modern cryptographers bringing mathematics into cryptography, publishes his book A Communications Theory of Secrecy Systems
1960's the Communications-Electronics Security Group (= CESG) is founded as a section of Government Communications Headquarters (= GCHQ)
late 1960's the IBM Watson Research Lab develops the Lucifer cipher
1969 James Ellis develops a system of separate public-keys and private-keys
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Leonard M. Adleman was one of three persons in a team to invent the
A mark (trademark or service mark) is "... a sign, or a combination of signs, capable of distinguishing the goods or services of one undertaking from those of other undertakings. The sign may particularly consist of one or more distinctive words, letters, numbers, drawings or pictures, emblems, colors or combinations of colors, or may be three-dimensional..." (
b. July 1, 1646, Leipzig
d. November 14, 1716, Hannover, Hanover
German philosopher, mathematician, and political adviser, important both as a metaphysician and as a logician and distinguished also for his independent invention of the differential and integral calculus. 1661, he entered the University of Leipzig as a law student; there he came into contact with the thought of men who had revolutionized science and philosophy--men such as