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== '''[[Block cipher]]''' ==
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In [[cryptography]], '''block ciphers''' are one of the two main types of [[symmetric cipher]]; they operate on fixed-size blocks of [[plaintext]], giving a block of [[ciphertext]] for each. The other main type are [[stream cipher]]s, which generate a continuous stream of keying material to be mixed with messages.
==Footnotes==
 
The basic function of block ciphers is to keep messages or stored data [[Information_security#Content_confidentiality | secret]]; the intent is that an unauthorised person be completely unable to read the enciphered material. Block ciphers therefore use a [[Key (cryptography)|key]] and are designed to be hard to read without that key. Of course an attacker's intent is exactly the opposite; he wants to read the material without authorisation, and often without the key. See [[cryptanalysis]] for his methods.
 
Among the best-known and most widely used block ciphers are two US government standards. The [[Data Encryption Standard]] (DES) from the 1970s is now considered obsolete; the [[Advanced Encryption Standard]] (AES) replaced it in 2002. To choose the new standard, the [[National Institute of Standards and Technology]] ran an AES competition. Fifteen ciphers were entered, five finalists selected, and eventually AES chosen. Text below gives an overview; for details of the process and the criteria, and descriptions of all fifteen candidates, see the [[AES competition]] article.
 
These standards greatly influenced the design of other block ciphers, and the latter part of this article is divided into sections based on that. [[#DES and alternatives | DES and alternatives]] describes 20th century block ciphers, all with the 64-bit block size of DES. [[#The AES generation | The AES generation]] describes the next generation, the first 21st century ciphers, all with the 128-bit block size of AES. [[#Large-block ciphers | Large-block ciphers]] covers a few special cases that do not fit in the other sections.
 
 
''[[Block cipher|.... (read more)]]''
 
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Latest revision as of 10:19, 11 September 2020

The Irvin pin. The eyes have always been red, but there are urban legends about the meanings of other colors.
A pin from another company, possibly Switlik or Standard Parachute. This style is common in catalogs and auctions of military memorabilia.

The Caterpillar Club is an informal association of people who have successfully used a parachute to bail out of a disabled aircraft. After authentication by the parachute maker, applicants receive a membership certificate and a distinctive lapel pin.

History

Before April 28, 1919 there was no way for a pilot to jump out of a plane and then to deploy a parachute. Parachutes were stored in a canister attached to the aircraft, and if the plane was spinning, the parachute could not deploy. Film industry stuntman Leslie Irvin developed a parachute that the pilot could deploy at will from a back pack using a ripcord. He joined the Army Air Corps parachute research team, and in April 1919 he successfully tested his design, though he broke his ankle during the test. Irvin was the first person to make a premeditated free fall jump from an airplane. He went on to form the Irving Airchute Company, which became a large supplier of parachutes. (A clerical error resulted in the addition of the "g" to Irvin and this was left in place until 1970, when the company was unified under the title Irvin Industries Incorporated.) The Irvin brand is now a part of Airborne Systems, a company with operations in Canada, the U.S. and the U.K.[1].

An early brochure [2] of the Irvin Parachute Company credits William O'Connor 24 August 1920 at McCook Field near Dayton, Ohio as the first person to be saved by an Irvin parachute, but this feat was unrecognised. On 20 October 1922 Lieutenant Harold R. Harris, chief of the McCook Field Flying Station, jumped from a disabled Loening W-2A monoplane fighter. Shortly after, two reporters from the Dayton Herald, realising that there would be more jumps in future, suggested that a club should be formed. 'Caterpillar Club' was suggested because the parachute canopy was made of silk, and because caterpillars have to climb out of their cocoons and fly away. Harris became the first member, and from that time forward any person who jumped from a disabled aircraft with a parachute became a member of the Caterpillar Club. Other famous members include General James Doolittle, Charles Lindbergh and (retired) astronaut John Glenn.

In 1922 Leslie Irvin agreed to give a gold pin to every person whose life was saved by one of his parachutes. By 1945 the number of members with the Irvin pins had grown to over 34,000. In addition to the Irvin Air Chute Company and its successors, other parachute manufacturers have also issued caterpillar pins for successful jumps. Irvin/Irving's successor, Airborne Systems Canada, still provides pins to people who made their jump long ago and are just now applying for membership. Another of these is Switlik Parachute Company, which though it no longer makes parachutes, still issues pins.

Footnotes

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