Mono-Alphabetic Substitution Ciphers.

Caesar or Shift Ciphers.

Julius Caesar, the first Roman emporer, is credited with inventing this type of cipher. To create a simple shift cipher all that you need to do is write out the alphabet and then write the alphabet out again, underneath, but shifted to the left or to the right.

An alternative is to use a cipher wheel to acheive the same effect.

Cut both wheels out. Stick one inside the other and turn the inner wheel to generate your cipher.

To encode your message all you need to do is work through your message (the plaintext) and convert it, one letter at a time, into ciphertext.

Decryption is the reverse of the process. You must know how much the alphabet has been shifted by or your message will be gibberish.

Symbol Substitution Ciphers.

These use a set of symbols instead of the latin alphabet. These codes are very easy to use on wordprocessors. First encipher your message using the cipherwheel or the strip of alphabet letters then highlight the text and convert the message into a crazy font.

Keyword Ciphers.

These use a keyword to generate the cipher. This is inserted at the start of the alphabet. Be very careful to avoid repeating letters either in the keyword or further on in the cipher alphabet. Messages are encrypted in the same way as before.

How to break these ciphers.

You need to understand exactly how the cipher works. Try writing your own messages with the cipher first. Can you guess any of the words or letters in the cipher? Look for single letters or repeated groups of letters. Look for one, two or three letter words. Try guessing but make sure that you know which letters are guesses and which are definite.

JavaScript Substitution Code Tools. Most tools that you will need on one webpage. Written in JavaScript so that you can download the source code and modify it.

The other tool that you need is frequency analysis. This helps you to guess which letter is which in the cipher. This page contains graphs and tools to carry this out.

Affine Shift Cipher

These use a mapping formula to produce a new alphabet. There are more details on the Affine Shift Cipher page but to break these ciphers treat then as a random single substitution cipher. Use frequency analysis to fine likely candidates for ETAOIN etc and then try to spot words like THE. Gradually work through the ciphertext guessing letters and words.

Liebnitz Ciphers.

Liebnitz Binary Specific adaption for codes in binary letter form, aaab abba baba etc.

Challenges.

Challenges. Challenges using the 26 letter english alphabet based on the cipher systems described in this section.

Symbol Challenges. Challenges using symbols alphabets based on the cipher systems described in this section.

EXCEL Programming

Simple Shift Cipher. Part 1Excel VBA Simple shift cipher. Using a spinner control to shift the alphabet.

Simple Shift Cipher. Part 2Excel VBA Using text boxes, command buttons and VBA programming to make and break mono-alphabetic substitution ciphers.

last updated 11th September 2011