Useful Resources | Easy Example | Caesar Code | Caesar Variant
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.
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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