CSE-100: Computer Technology and its Impact on Society
Computer Science and Engineering
University of Pennsylvania
Fall Semester 2003
Matt Huenerfauth.
October 3, 2003
You can download the slides from lab 04 from here.
They in PowerPoint format.
We will be breaking come codes today in lab! See the slides for instructions.
We will be using the following tools:
First look at this sample of text that has been encoded using a substitution cipher. cipher-text.html
Letter frequency - Use this applet to count the frequency of the code letters in the encoded text.
You should print out the following page to record the results
from above: letter-chart.html
You will also need a copy of this page: alphabetized.html
Some sources of information on letter frequencies.
(Letter rankings differ based on how you count.)
http://deafandblind.com/word_frequency.htm
http://storm.prohosting.com/~glyph/crypto/freq-en.shtml
Now try to guess what the original letter was for each of the code letters in the ciphertext.
Cryptogram applet - Use this applet to replace code letters with original letters as you figure them out. (Click the blue words: "click here to view this site.")