 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 3 4 5 ] Next Last |
The cipher is often described in such terms as "perfectly secure" and "provably, absolutely, unbreakable". This is quite correct in theory; the method was proven unbreakable in an information-theoretic sense by Claude Shannon. However, it has severe drawbacks in practice: it requires secure exchange of the one-time pad material, which must be as long as the message; and careful treatment to make sure that it is disposed of correctly and never reused — hence "one time". These implementation difficulties have led to examples of one-time pad messages being broken (for example, VENONA), and are so serious that they have prevented the one-time pad from being adopted as a widespread tool in information security.
Each character in the message is combined with one from the (random, secret, and used only once) pad in the manner of a Vernam cipher. So the pad must be at least the length of the message. Theoretically there is no way to decipher the message without knowing the contents of the pad. For this reason it is very important that the pad be protected (ie, secret), random (ie, unpredictable by anyone), and used only once, lest the cipher be easily compromised.
The history of the one time pad is marked by four separate but closely related discoveries.
The first one time pad system was electrical. In 1917, Gilbert Vernam (of AT&T) invented and later patented ( US patent 1310719) a cipher based on teletype machine technology. Each character in a message was combined with a character on a paper tape key. Captain Joseph Mauborgne (then a Captain in the United States ArmyThe Army is the branch of the United States armed forces which has primary responsibility for land-based military operations. As of fiscal year 2002 (FY02), it consisted of 480,000 soldiers on active duty and 555,000 in reserve (350,000 in Army National G and later chief of the Signal CorpsThe Signal Corps is a military branch, usually subordinate to a country's army. Many countries have a Signal Corps, whose main function is usually communication (in modern times, usually radio communication on the battlefield). The word corps is used in t) recognized that the character on the key tape could be completely random. Together they invented the first one time tape system.
The second development was the paper pad system. Diplomats had long used codeFor other senses of the word "code", see code (disambiguation). In communications, a code is a rule for converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same sort. In cos for confidentiality and to minimize telegraph costs. Words and phrases were converted to groups of numbers (typically 4 or 5 digits) using a dictionary-like codebookJoseph Hooker’s code clerk In cryptography, a codebook is a document for implementing a code. A codebook contains a lookup table for coding and decoding; each word or phrase has (one or more) strings which replace it. To decipher messages written in code,. For added security, secret numbers could be added to each code group before transmission, with the secret numbers being changed periodically. In the early 1920sCenturies: 19th century 20th century 21st century Decades: 1870s 1880s 1890s 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s Years: 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 Events and trends Technology John Logie Baird invents the first working t, three German cryptographers, Werner Kunze, Rudolf Schauffler and Erich Langlotz, who were involved in breaking such systems, realized that they could never be broken if a separate additive number was used for every code group. They had duplicate paper pads printed up with lines of random number groups. Each page had a serial number and eight lines. Each line had six 5-digt numbers. A page would be used as a work sheet to encode a message and then destroyed. The serial number of the page would be sent with the encoded message. The recipient would reverse the procedure and then destroy his copy of the page. The German foreign office put this system into operation by 1923Centuries: 19th century 20th century 21st century Decades: 1870s 1880s 1890s 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s Years: 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 Events January 1 Grouping of all UK railway companies into four larg.
A separate notion was the use of a one time pad of letters to encode plaintext directly as in the example below. Leo MarksLeopold Samuel Marks ( September 24, 1920 January 15, 2001) was an English cryptographer and scriptwriter. Early life Born the son of an antiquarian bookseller in London, he was first introduced to cryptography when his father showed him a copy of Edgar A describes inventing such a system for the British Special Operations Executive during World War II though he suspects it was already know in the highly compartmentalized world of cryptography.
The final discovery was by Claude Shannon in the 1940s who recognized and proved the theoretical significance of the one time pad system.
| Politics | Business | Finance |
 |
 |
 |
|