Description
Purpose
The purpose of this assignment is to familiarize you with basic encryption schemes and how to derive
a decryption function from a known encryption function. Additionally, this assignment will familiarize
you with Python (or the programming language you choose) and writing a simple decryption function
in Python (or your programming language). You will learn how to read encryption code, deriving the
corresponding decryption function (which is the inverse function of the encryption function),
implementing the decryption function, and applying the decryption function on a given input string.
Objectives
Learners will be able to:
● Read encryption implementation of the Caesar cipher.
● Implement their own decryption function for a Caesar cipher.
● Deal with files programmatically.
● Decrypt a given ciphertext that is encrypted using a Caesar cipher and its corresponding key.
Technology Requirements
The reference encryption code is provided as a Python script; however, you may implement your
solutions in any programming language that you choose.
Note: The course team will not be able to help you if you choose any language that is not Python,
Java, or C#; therefore, to create the best learning experience, Python is strongly recommended.
CSE 543
Ceasar Cipher Assignment 1
Assignment Description and Directions
Technology Setup Reminder
If you have not already joined the course’s pwn.college, please review the setup directions in Module
0: Welcome and Start Here of your course to properly gain access and start your work.
Accessing the Assignment
Once you have joined the course’s pwn.college session:
1. Navigate to https://pwn.college.
2. Click “Login” in the upper right corner of the screen and enter your account credentials.
a. Click “Forgot your password?” if you have trouble logging in.
3. Navigate to “Dojos”, second option from the left at the top of the screen.
4. Under “Courses”, select “CSE 543 – Session X Year”.
5. Under “ Modules”, select “Caesar Cipher Assignment”.
6. Under “Challenges”, click on “Caesar Cipher”, read the details, and then click “Start” when
you are ready to work.
a. Optional: use “Practice” to help you work through the level with assistance.
Assignment Directions
For this assignment, you will use three files. All three files are under /challenge/ in the virtual
environment.
1. `ciphertext.txt` – A ciphertext encrypted with a Caesar cipher.
2. `caesarkey.txt` – The key used for the Caesar cipher. It is the stdout output when running
`caesar.py` to encrypt the plaintext.
3. `caesar.py` – The reference implementation of the Caesar cipher with only the encryption
feature.
You will need to write some code so you can plug in the key and decrypt. Here are recommended
steps to solve the problem:
CSE 543
Ceasar Cipher Assignment 2
1. The Caesar cipher that is used in this assignment is a standard (and ancient) encryption
algorithm. You may find its description on Wikipedia. Please read the description first.
2. (Optional) A reference implementation of the Caesar cipher is provided in `caesar.py`. If you
are new to Python, you are strongly recommended to read and understand the
implementation.
3. Open `caesarkey.txt` and find the key: the offset that was used during encryption.
4. Think about how the encryption can be inverted.
5. Write a program that will open `ciphertext.txt`, read out the content, shift the characters by the
given offset (which is the decryption process), and write the decrypted content into a new file.
The alphabet for the plaintext and ciphertext is the capital letters [A-Z], and the key is a number
between 0 and 25. This means your decrypted text (plaintext) should only have capital letters.
You should run /challenge/challenge.py to verify the correctness of your program, and get the flag if
your program works as expected. You must then submit your program and the writeup to the
submission space provided in this course.
Debugging tips: In case you find your decryption code not working as expected, you may first
manually decrypt the first few characters in `ciphertext.txt`. Then you may print out results after each
statement in your code and verify the results against your manual decryption.
Submission Directions for Assignment Deliverables
You are given an unlimited number of attempts to submit your best work. The number of attempts is
given to anticipate any submission errors you may have in regards to properly submitting your best
work within the deadline (e.g., accidentally submitting the wrong paper). It is not meant for you to
receive multiple rounds of feedback and then one (1) final submission. Only your most recent
submission will be assessed.
You must complete your Caesar Cipher Assignment deliverables in pwn.college and then submit
the deliverables in its submission space in the course. Carefully review submission directions
outlined in this overview document in order to correctly earn credit for your work. Learners may not
email or use other means to submit any assignment or project for review, including feedback, and
grading.
The Caesar Cipher Assignment includes three (3) deliverables submitted as one (1) ZIP file:
● Program/Code: Please include the code you have written for the assignment.
● Decrypted Message: Attach the decrypted message you obtained from your code, saved as a
.txt file.
CSE 543
Ceasar Cipher Assignment 3
● Solution Write-up: Provide a write-up detailing how you solved the assignment problem. This
should also be saved as a .txt file.
Making File Submissions in Canvas
Before submitting, confirm that your deliverables follow the requirements for the project, and then
submit your work in the designated submission space in the course. Your submission will be reviewed
by the course team before finalizing your assignment grade.
1. In your course, go to Submission: Caesar Cipher Assignment.
2. Click Start Assignment.
3. Click Choose File.
4. Locate and select one (1) deliverable file from your device.
5. If needed, click +Add Another File and repeat Steps 3 and 4 until all deliverables are added.
6. Select the agreement and then click Submit Assignment.
7. (If needed and allowed) To resubmit files:
a. Return to the Canvas submission space, click New Attempt, and repeat the process
from Step 3.
Evaluation
Your submission will be automatically graded in the challenge environment. As you complete each
challenge, you will receive a score in pwn.college. Scores will automatically populate to the course
after completion or after the due date passes. You will earn the maximum number of points for the
corresponding assignment in Canvas if you earn 100% on the challenge in pwn.college. Please refer
to the Course Grade Breakdown in the syllabus PDF and the assignment submission space in
Canvas so you know how many points each assignment is worth.
Your deliverables will be reviewed by the course team before finalizing your assignment grade. No
credit will be given for missing or incorrect submissions.
Review the course syllabus for details regarding late penalties.
● You will earn full credit if your decryption result is fully correct.
● If your decryption is incorrect, you will not earn credit.
● Partial credit will not be granted for this assignment.
CSE 543
Ceasar Cipher Assignment 4
If your decryption works correctly, you will see multiple meaningful sentences in English as the
plaintext (uppercase letters only, with no spaces between words). Otherwise please go back and fix
your implementation.
