Prizecodebreaker

 

 

Useful Resources | Easy Example | Caesar Code | Caesar Variant

Simon Singh’s web site

Simon Singh is an author, journalist and TV producer specialising in Science and Mathematics. His best selling book plots the history of cryptography as well as demonstrating many of the cryptographic techniques used in the competitions on this site. The book can be found at Amazon by following this link.

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At the back of his book he sets a Cipher Challenge of 10 different secret messages with a £10,000 prize for the first person to correctly decipher them. The challenge was solved on the 7th October, 2000, after a year of arduous effort. The winning team consisted of Fredrik Almgren, Gunnar Andersson, Torbjorn Granlund, Lars Ivansson and Staffan Ulfberg.

Download the 40 page report on how they solved the Cipher Challenge here.

Tutorials

The Internet has many Cryptographic Tutorials for both Classical and Modern techniques. Some of my favourite tutorials that cover Ceasar, Multiplication, Linear, Polyalphabetic and RSA ciphers are shown below. All these sites also include many free Crypto tools. The first site has a fast Caesar tool that does all 26 shifts in one go (this makes decoding Jim Halpern’s message on the front of this site a snap!)


Polyalphabetic Ciphers

Frequency analysis and good word skills can defeat most substitution ciphers fairly easily. The problem is that once a symbol substitution has been correctly ascertained then each occurrence of that symbol in the cipher can also be updated.

To overcome this weakness Polyalphabetic Ciphers were developed where the same symbol very often stands for a different letter on each occurrence, making it much harder to decode.

Probably the most famous polyalphabetic code is the Vigenere cipher that was created about 400 years ago. Descriptions of the Vigenere cipher can be found in the tutorials above. However, the applet at the following link has an excellent Vigenere encryption and decryption machine. However the passkey must also be known and inserted to perform decryption.

Inforenz Limited is a security company that helps recover encrypted and concealed data for law enforcement agencies and commercial organisations. Diana Dors, the actress, left a Vigenere cipher for her son Mark giving him a clue to the whereabouts of her missing £2M fortune. Inforenz cracked the code that held the secret, without knowing the passkey, with a clever analysis program that they developed. This story was the subject of a television documentary earlier this year. To download this program click here.

The famous German Enigma machine that was used in WWII is an example of an even harder non-substitution cipher. The following applet provides an amazing simulation of this machine. For coding or decoding you must correctly set the position of the rotors and plugboard

 

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