Math/CS 323. Cryptography

Fall 2025

Instructor: Enrique Treviño
Lectures: MW 1:00pm - 2:20 pm in Brown Hall 315
Office Hours: MTWRF from 9:15am to 10:00am, T from 10am to 11am and 1pm to 2:30pm, and R from 1pm to 2:30pm. You can also arrange a meeting by appointment.
Office: Brown Hall 123
Email:
Phone Ext.: #6187

Announcements

Announcements will appear here.

Course Description

An introduction to cryptology and cryptanalysis, the making of codes and the breaking of codes. History and basic concepts. Classical ciphers and attacks on classical ciphers. One-time Pad. Modern ciphers including DES, AES. Public key ciphers including RSA and Diffie-Hellman. Digital signatures. Additional topics may include Elliptic Curve systems, knapsack systems, and other cryptographic systems. Prerequisites: Mathematics 230 and Computer Science 212, or permission of the instructor. (Under the old GEC, this course meets the Natural Science & Mathematics requirement.)

Textbook

Cryptography by Simon Rubinstein-Salzedo.

Student Learning Outcomes

Main Goals:

Understand what cryptography is.
Be able to encode plaintext using various methods.
Be able to decode cyphertext in some cases.
Be able to program encoding and decoding.
Learn some number theory

Grading

The course grade will be based on:
Homework 10%,
Midterms 60% (20% each),
Final Exam 30%.

Homework

There will be written homework roughly every week. The homework will be posted on Moodle.

Exams

There will be three two-part midterms and one two-part final exam. The midterms will be split into a hand-written test and a computer-based exam outside of class. On the midterms and the final exam you must work on the problems on your own. No collaboration permitted in the exams.

The tentative dates for the exams:

The first in-class midterm will be on Monday September 29. The online portion of the exam (through Moodle) will be opened from September 29 to October 4.
The second midterm will be on Wednesday November 5. The online portion of the exam (through Moodle) will be opened from November 10 to November 15.
The third midterm will be on Wednesday December 3. The online portion of the exam (through Moodle) will be opened from November 30 to December 5.
The final exam will be on Friday December 12 from 1:30pm to 4:30pm. The online portion of the final (through Moodle) will be opened from December 7 to December 12 (at Noon).

Attendance

Students are expected to come to every lecture and every exam.

If the dates of the exams conflict with Lake Forest approved events, inform me as soon as possible.

Description of instructional time and expectations:

This course meets 3 times per week for 3 hours per week. The course carries 1.0 course credit (equivalent to four semester credit hours). Students are expected to devote a minimum of 12 hours of total work per week (in-class time plus out-of-class work) to this course.

Academic Honesty

Please read the College's information on Academic Honesty. If a student cheats in an exam, quiz or homework assignment, I will proceed with charging the student with the Academic Honesty Judicial Board. The usual (first) penalty is a 0 in the assignment on which the cheating occured plus some ethics lectures the student would take. The second penalty is usually suspension. For the online exams and homework assignments, copying code from any website is considered plagiarism (including using ChatGPT). I will ask all students to explain their code used on exams verbally to me by appointment. If the explanation for their code is unsatisfactory, the grade for that exam will be 0. My recommendation is to only turn in answers for questions on which there is code you can explain yourself.

Academic Resources, Protocols, and Policies

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Last modified on October 9, 2025.