Unit 5: Cryptography
The key concepts of public key cryptography are introduced.

By: CSP-Alabama

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Unit 5: Cryptography - Video

Introduction to Cryptography: Part 1 - Private Key
This outlines private key encryption and some key cracking. Code examples are at: http://asecuritysite.com/encryption.

By: Bill Buchanan

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Introduction to Cryptography: Part 1 - Private Key - Video

Network Security Part 5 Cryptography

By: Navin Skills

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Network Security Part 5 Cryptography - Video

Secret Key Cryptography - AES using OpenSSL
Demo of AES encryption in both ECB and CBC mode using OpenSSL toolkit.

By: IITB Cyber Security

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Secret Key Cryptography - AES using OpenSSL - Video

Public Key Cryptography - RSA using OpenSSL
Demo of RSA using OpenSSL toolkit in linux.

By: IITB Cyber Security

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Public Key Cryptography - RSA using OpenSSL - Video

The wireless telegraph station in Sayville, New York was one of the most powerful in the world. Constructed by the German company Telefunken in 1912, it served as a transatlantic relay point for diplomatic messages and business communications. It was a beacon among amateur wireless enthusiasts around the United States who could tune their home-made sets to the station's nightly press dispatches. All of this changed when one of those amateurs uncovered the station's true purpose.

The Navy seized the station in 1915 on suspicion of relaying covert commands from the German Empire to U-Boats in the Atlantic, and a congressional bill was introduced to ban all civilian wireless activities from the airwaves. The interruptions to the story that follows consist of excerpts from Hugo Gernsback's serial novel The Scientific Adventures of Baron Mnchausen, which ran in Electrical Experimenter magazine right as news of the wireless cryptography scandal unfolded.

Static was always a problem as the summer heat rolled in.

Situated on a hundred-acre plot along the Long Island coastline and dropped in a mosquito-infested field, the Sayville wireless plant began experiencing the seasonal interference that comes with longer days and warmer weather in May 1915. At that point little older than the twentieth century itself, wireless telegraphy (a precursor to radio) was not an entirely reliable medium. Debates over the precise cause of this seasonal static soon broke out among the tinkerers and oddballs of the early wireless community. Some said that radio waves experience more interference as they propagate through denser, more humid air. (There was still talk at this time of the existence of a luminiferous aether.) Others speculated that because messages came in clearer at night, the heat of the summer sun on the station's aerials was affecting their transmitting capabilities.

By late summer, Sayville operators announced that interference from so-called equinoctial storms was forcing them to restrict messages to official government communications. Some commenters quipped that wireless buffs were getting cause and effect mixed up: "they said the electrical effects [of the station] absorbed all the moisture and made Sayville dry as a Saratoga chip," referring to the potato chip first invented in Saratoga Springs, NY in the 1850s. Perhaps the station itself was altering its surrounding atmospheric conditions.

When one contemplates the marvel of sculptured sound on a graphophonic record, and realizes that from the cold vorticity of line there may magically spring the golden lilt of the greatest song voice that the world has ever heard, then comes the conviction that we are living in the days of white magic.

At the rate of a dollar per word, civilians and government officials alike could relay messages from Sayville to its sister station at Nauen, Germany. In addition to commercial and diplomatic communications, Sayville sent out press dispatches every night at 9:00 that amateurs around the country tuned in to using their hand-built crystal detector sets. Receiving transmissions from the Sayville station was the gold standard for both wireless sets and their owners (who referred to themselves as 'muckers'), and electronics manufacturers regularly promised easy reception of Sayville transmissions in advertisements for their products. The static that came with summer weather was nothing new for these wireless professionals and amateurs. Seasonal disturbances were simply a part of the natural rhythms of a new medium.

A 1907 crystal radio receiver housed in mahogany, designed by Harry Shoemaker in 1907. History San Jos, Perham Collection.

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U-Boats, Spies, and White Magic: The Invention of Wireless Cryptography