CSC-233: Assignment #1, Winter Quarter 2026

Introduction

Remember that you will receive nearly full marks simply for turning in an assignment that shows that you made a legitimate attempt at working through the problems. (Though for the most part, you should be able to do them correctly -- even the cryptanalysis questions are rarely that difficult).

Problem #1

Part A:

The following ciphertext message has been enciphered using a Caesar shift.

JSHNYNSL F RTG YT XYTWR YMJ HFUNYTQ NX ZSIJRTHWFYNH.

However, the shift may not be 3. You could, of course, try all 25 shifts - but to save the time, invest a few minutes thinking about letter frequencies, patterns and so on. If you do this, you should be able to nail down the shift to just 2 or 3 possibilities.

Once you have a couple of candidate letters that you suspect are likely to be correct, ask yourself what shift that would be.

Test each one. You will quickly know if a candidate key (shift) resembles an English message.

To keep things relatively simple, spaces have been preserved. That is, the spaces in the ciphertext match the spaces in the plaintext.

As part of your submission, be SURE to indicate your thinking in terms of how you attacked this cipher.

While you can almost certainly solve this problem without it, as part of your submission, also do a pattern search on the last word which is 12 characters long. Explain how you did this in your answer. Remember to use this website: https://www.dcode.fr/word-pattern-search

Part B:

Repeat with the following ciphertext:

thao pz ptwvyahua.

Hints:

• There are no 'e's in the plaintext.

• The word "the" is not present

• There IS a two letter word -- and you know there must be a vowel in there somewhere. To save you some time, I will tell you that the first character is the vowel.

NOTE: As with part A, an important part of your answer is explaining how you approached solving the problem.

Problem #2

1. Create a Polybius cipher using the keyword: EUREKA

2. Then encipher the text: Archimedes bathtub.

3. Decipher the following ciphertext: 2311 3544 3245 5441 2425 4133 23

Problem #3

Just some course housekeeping.

In your document answer the following questions / statements. They can all be found on the syllabus.

1. Why is it important to subscribe to D2L news postings? Then write a statement indicating that you have subscribed to news postings. Sign this statement by simply typing your name at the end.

2. If you have a (non-personal) question relating to course topics, what is the preferred place in which to ask it? (Email the prof? Tutoring center? Something else?)

3. Online students: Please write a statement indicating that you are aware that there are three exams for the course, and that they must be taken in a proctored location. Please "sign" your name to this statement by simply typing it int your document.

Submission Requirements

• Type all of your answers into a Word document. PDF is NOT acceptable.

• Upload your Word document to the D2L submissions page.