MATH 4350
Number Theory and Cryptography
The course will cover many of the basics of elementary number theory, providing a base from which to approach modern algebra, algebraic number theory and analytic number theory. It will also introduce one of the most important real-world applications of mathematics, namely the use of number theory and algebraic geometry in public key cryptography. Topics from number theory involve divisibility (Euclidean algorithm, primes, Fundamental Theorem of Arithmetic), congruences (modular arithmetic, Chinese Remainder Theorem, primality testing and factorization). Topics from cryptography will include RSA encryption, Diffie-Hellman key exchange and elliptic curve cryptography. Topics about algebraic numbers may be include if time permits. Prerequisites: Math 233, 309 and 310 (or permission of instructor)
Instructors
Reviews
I really like professor Johnson. He cares so much about the material and his students. The first exam might've been a bit too hard but the final was very fair and we had 2 take-home exams. Psets could get a bit lengthy, but the exams were always easier than the Psets. Would recommend if you love math!
5/12/2024
Johnson is the best professor I have had in the Math department. His lectures are great and he cares about the material. He also cares about his students and goes out of his way to help students. Highly recommend taking this course with him.
5/10/2024
Professor Johnson was a great professor to take number theory with. He is very knowledgeable about the subject, and he did a good job explaining the material during lectures. I felt the exams were fair, and we were given two take-home exams to help de-weight the in-person exams. He also offered lots of extra credit opportunities on PSets and exams.
5/10/2024
This class is so disappointing. As a math major, I was so excited about Number theory and cryptography. but this class has been more annoying than fun and has destroyed my self esteem. Prof. Johnson is a good lecturer but makes the class so inaccessible almost. The problem sets take at least 10 hours and the exam was graded SO harshly.
3/21/2024
What went from being my favorite class at the beginning of the semester is now my most dreaded, scary, difficult, impossible class. He's not understanding of our time or responsibilities outside of this class and expects us to spend hours on HW while giving us the most impossible exams. Steer clear of this class if you want to keep your sanity.
3/21/2024
Came to rate my professor cuz I thought I was the only one feeling terrible about this number theory class. But looks like theres a ton of others that feel this way as well. I guess it speaks for itself, just don't take MATH4351 with Silas Johnson.
3/21/2024
Bro didn't release exam statistics because of how horribly it went. The only thing that can save me now is Jesus.
3/21/2024
Even so much as thinking about this class genuinely makes me want to cry
3/21/2024
I want to like this class so bad because Prof Johnson is nice, the content is interesting, and people in the class seem helpful. It is just way too difficult and feels like a full time job with overtime. So I have come to despise it which definitely makes me feel a little sad as a math major.
3/21/2024
I can't take this anymore. I am spending so much time on this class yet doing the worst in it. I feel like I've lost my sense of pride in my work and all sense of feeling about how I perform. Someone said the class feels inaccessible and I've never agreed more. I wish i had advice to not take this class before i jumped in head first.
3/21/2024
I genuinely do not think it is possible to get an A in this class. The HW assignments are graded so harshly, and the exam averages are incredibly low.
3/5/2024
Prof. Johnson is a good lecturer and a terrible grader. He wanted us to learn how to write rigorous proofs so he took off major points on the weekly problem sets for the most trivial errors. Not to mention the problem sets probably took around 5 hours on average to complete. I wanted to like him, but this class was more annoying than fun.
2/17/2024
Schaefer is the actual GOAT of the math department. 4351 is my favorite math class I've taken here, and it's all due to Karl. If he's teaching a class you want to take, then take it. He is a generational talent in the math department.
2/1/2024
Schaefer is definitely one of the best math professors at WashU! Humorous and gives very clear lectures. Very helpful in office hours. I really enjoyed taking this class with him.
5/12/2023
Prof Johnson is super nice and adapted the class extremely well to the pandemic. You can tell he actually cares about his students and really loves teaching. He is very receptive to emails and is helpful in office hours. The class is pretty homework heavy and was a lot of work but you get the grade you work for. Would definitely recommend.
5/22/2020