ACCESS - Cryptography
Frequency analysis for substitution cyphers
ACCESS Home > Frequency Analysis
- Stage 0: Caesar or shift cypher
- Decode this important message by finding the right key. (inspired from the Java Applet here).
Stage 1: A short (and ironic, depending on the weather) message
- Open Maple (Applications > Engineering and Math).
- Copy the link address for this Maple file: substitution.mw
- Go to Maple > Open URL and paste the link in the clipboard (On a Mac Paste is ⌘-v).
- Before you change anything: Save a local copy of substitution.mw into a directory (call it say
Crypto
).
- Use Maple to do frequency analysis and the actual decoding. It helps to use lower case letters for clear text and upper case for encrypted text.
- A frequency table is here.
Stage 2: A longer message.
- Download and open in Word the encrypted document corresponding to your
group:
group1.doc,
group2.doc,
group3.doc,
group4.doc,
group5.doc,
group6.doc,
group7.doc.
- Use Maple to perform a frequency analysis and decoding. (You may also use
Word's search and replace, making sure you enable case sensitivity)
- If you have time: Use the internet to figure out something about the
person whose name the cypher keyword was made from (by eliminating duplicate
letters).
Stage 3: Discussion.
- Let's read our results out loud to the class to hear the whole story. (This essay was found by Professor Emina Alibegovic who once was a graduate student TA for ACCESS)
- If you would like to know more, please visit the Women in Math Project, maintained by Professor Marie Vitulli of the University of Oregon. (Thanks to Emily Putnam, who helped with ACCESS a number of years ago, for this link.)
- If you have time: you could read about Vigenère's Chiffre Indechiffrable (Chapter 2 in "The Code Book") which actually was dechiffrable, and then use and modify the Maple code to break the stage 4 cipher on page 355.