Math/CS 323. Cryptography

Fall 2021


No class on Friday September 10.

I cover Chapter 4 in a different order than the textbook. Here are some lecture notes that are more similar to the order I teach Number Theory:
Number Theory Lecture Notes.

Homework assignments are 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.

Cryptography by Simon Rubinstein-Salzedo.

Student Learning Outcomes

Main Goals:


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


There will be written homework roughly every week. A copy of the first homework assignments can be accessed here. The homework assignments will be submitted through Moodle. Collaboration in the homework is permitted, but your work must be your own.


There will be three two-part midterms and one 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:


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. The code you write for exams and homework should be your own. Failure to write your own code will be considered academic dishonesty.

COVID-19 Precautions

It is recommended to have a plan on how to get notes in case you need to be quarantined.

Accommodations Statement

If you are a student who needs an accommodation because of a disability or medical or psychological condition that limits your ability to fully participate in this course, please contact Kara Fifield, Director of Disability Services, to document your disability with the College and with the professor of this course. Academic accommodations should be reasonable and not alter the fundamental nature of this course. Because it can take a week or more to arrange requested accommodations, you are encouraged to establish your semester accommodations as early in the semester as possible. Contact Kara Fifield by email or phone: or 847-735-5167. For more information about services for students with disabilities at Lake Forest College, see:

You are also welcome to contact me privately to discuss your academic needs. However, all disability-related accommodations must be arranged through Kara Fifield.

Last modified on September 8, 2021.