For ease of use, this has been divided into sections as listed below, together with a brief description of their purpose and content. The [size] of each is given in kilobytes as guide to downloading times. Each requires the use of an Acrobat Reader to allow it to be viewed and printed out.
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Notes [60 k] |
Essential reading whether using just a part or the whole of this material. Includes a short vocabulary with some definitions, and a list of some well-known names in the history of cryptology. There is also list of further sources of information.
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Scrambled Messages [30 k] |
How an ordinary message can re-arranged, in an orderly manner, so as to make it very difficult to read.
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Buried Messages [40 k] | Disguising a message so that it does not even look as though it contains any secrets. |
Coded Messages [20 k] | Using a code allows messages to be hidden and shortened at the same time. |
Simple Cipher Messages [70 k] | Hiding the messages by substituting other letters for those of the original text |
Addition Ciphers [20 k] | Using numbers and some simple arithmetic to hide a message |
Multiplication Ciphers [20 k] | How more complex arithmetic processes bury the messages even deeper. |
Rotor Ciphers [70 k] | Mechanical enciphering with a (very!) simplified paper model of the Enigma machine. |
Cryptanalysis [40 k] |
The science (or is it an art?) of breaking cipher messages, allowing them to be read without knowing the keyword or its equivalent. |
Other Systems [50 k] | Accounts of some other methods for creating ciphers. |
Public Key Ciphers [60 k] | How one particular modern cipher system (RSA) works, and can be made widely available to all, whilst retaining its security. |
Additional Materials [40 k] | While all sections contain their own support materials, this has a few more general items. |
The Small Code Book [40 k] | An abbreviated code book which can be printed out and assembled. For use with Coded Messages (above). |
Display Material [70 k] | Diagrams suitable for making ohp slides or even projected directly onto a suitable screen or whiteboard. |
The Gold Bug [80 k] |
The famous short story by Edgar Allen Poe about cipher breaking which was the first account to appear in a work of fiction. |
The Dancing Men [80 k] | The story of how Sherlock Holmes broke a symbol cipher. |
The Enigma Machine [50 k] | Picture of the most well-known ciphering machine |
The SIGABA Machine [330 k] | Picture of the US equivalent of the Enigma machine. The British TypEx machine was similar to this one. |
The Hagelin Machine [80 k] | Picture of the Hagelin M209 machine. This was a portable (purely mechanical) enciphering machine. |
Answers [20 k] | Available yes, but a password will be needed to read this file. |