4003-440-02 Operating Systems I
Encrypted Grades

Encrypted Grade Files
Procedure for Decrypting Grades
Example Grade File

ajw6717 amb2189 amb8120 cac3479 cda8519 egs9108 eht4790

esw5886 ijd8975 jdk3414 jei3137 jml8721 jmv8443 joh9446

jrg1541 jrk2596 kkl4549 kxb3695 kxz6102 lgs8331 lts6443

lxl5734 mar1491 mdr5829 mgp6782 mlb7687 mrf1379 mrp3178

mwh1617 nnd5623 ntb5216 oxv5945 rco5918 slb1566 smw9082

sps5688 tjh2430 xxs2429 zsb1244 zsn2231

To decrypt your grade file:

1. Obtain your secret key from me, in person. You must show me your student ID. Your secret key is a 16-digit hexadecimal number composed of the numerals 0-9 and the letters a-f. I will announce in class when the secret keys are available.

2. Download your own encrypted grade file from the Encrypted Grade Files section above and store it in a file on your machine.

3. Run the encrypted grade file viewer program, which is installed on the Computer Science Department computer systems. In your Computer Science Department account, type this command:

   java -classpath /home/fac/ark/public_html/cscl.jar edu.rit.crypto.gradefile.View <file>
   

   replacing <file> with the name of the file where you downloaded your encrypted grade file. Enter your secret key when the program asks for it.

You can also set up your web browser so it automatically runs the encrypted grade file viewer program when you click on your grade file link. The web server sends the encrypted grade file with a special MIME type of application/x-ark-edu-rit-crypto-gradefile. Create a shell script to run the viewer, then configure your browser to run the shell script when a file is downloaded with that MIME type. Here is an example of a shell script named viewgrade:

#!/bin/bash java -classpath /home/fac/ark/public_html/cscl.jar edu.rit.crypto.gradefile.View $1

The encrypted grade file viewer program is part of the Computer Science Course Library. You may install the Library on your own personal computer so you can view your grades on your own system. To learn how the encrypted grade file viewer program works, you may examine the Java source code:

Class edu.rit.crypto.gradefile.View
Class edu.rit.crypto.gradefile.GradeFileContext01

You can test the above procedure using the example grade file below. It has been encrypted with the following secret key:
c613 cbe9 be87 e1de

example

Cryptography • 4003-482-01/4005-705-01 • Spring Quarter 2013

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Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706

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Copyright © 2012 Alan Kaminsky. All rights reserved. Last updated 11-Dec-2012. Please send comments to ark­@­cs.rit.edu.