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Learner Reviews & Feedback for Number Theory and Cryptography by University of California San Diego

538 ratings

About the Course

A prominent expert in the number theory Godfrey Hardy described it in the beginning of 20th century as one of the most obviously useless branches of Pure Mathematics”. Just 30 years after his death, an algorithm for encryption of secret messages was developed using achievements of number theory. It was called RSA after the names of its authors, and its implementation is probably the most frequently used computer program in the world nowadays. Without it, nobody would be able to make secure payments over the internet, or even log in securely to e-mail and other personal services. In this course we will start with the basics of the number theory and get to cryptographic protocols based on it. By the end, you will be able to apply the basics of the number theory to encrypt and decrypt messages, and to break the code if one applies RSA carelessly. You will even pass a cryptographic quest! As prerequisites we assume only basic math (e.g., we expect you to know what is a square or how to add fractions), basic programming in python (functions, loops, recursion), common sense and curiosity. Our intended audience are all people that work or plan to work in IT, starting from motivated high school students....

Top reviews


Jul 31, 2020

I loved this course! It is unlike any I have taken before. All courses in this specialization have always included fun activities to make the taught content fun and understandable.


Nov 21, 2018

I was really impressed especially with the RSA portion of the course. It was really well explained, and the programming exercise was cleverly designed and implemented. Well done.

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26 - 50 of 115 Reviews for Number Theory and Cryptography

By Sourav M

May 12, 2018

Very nice course for beginners

By Kristen P

Feb 6, 2020

Challenging yet fun course!

By Kuldeep K

Apr 29, 2020

I learnt many new things.

By Jakub D

Sep 8, 2019

Good introduction


Sep 16, 2019

very usefull

By danish m

Apr 26, 2020

nice course

By HaotianWang

Jul 19, 2018



May 15, 2020

It was challenging and interesting. The only issue what I feel is that I am not from a coding background, so to understand the coding concepts were a bit tough. And I asked my queries through forums, but no reply came. But overall, it was an interesting course

By Juliano P

Jan 2, 2021

This is the worst module so far, not at all comparable to the first module of this specialization.

This is not a total beginner's content, but the videos are spoken too fast, like the professor was pressured to make it as short as possible. I had to watch some of the videos at 0.8x speed, instead of my usual 1.3x. Moreover, this was the first time I slow down a video.

Several lessons were just read from the slides followed by a long abstract mathematical digression without any companion material (ie, slides), so you have to listen and imagine all the variables and formulas in your head, since there is no illustration or guide of what is being said. I'm a visual learner, what makes it even worse.

Be prepared to look for resources elsewhere if you take this course and you are not familiar with module arithmetic. I'm not exaggerating when I say most of what I learned in this module were from YouTube videos... at least this module gave me a structured syllabus and topics to look for.

Also, compared to the previous modules, it lacks a lot on exercises and questions to fix the subject. The code exercises were most often cryptic for me and demanded lots of trial and error. The reason for this were the poor explanations and the requirement to use the algorithms introduced in class, which were not always what YouTube videos used.

I was expecting it to be more step by step, but I feel like it is a quick review for people who have taken the subject before.

By Ahmad A

Jul 15, 2021

You will know finally the Ultimate Answer to the Ultimate Question of Life, the Universe, and Everything :) ================================= If you are taking the course anyway, my "ultimate" advice to you would be that when you reach the last week, DUPLICATE(make a copy) YOUR RSA QUEST NOTEBOOK before you try solve the quest Because you may make a mistake and you won't be able to reset your notebook ================================= The course is great but Week 3 is pure math and equations so much so be prepared but Week 4 would is the best if you manage to complete RSA Quest !!!

By Christopher W

May 10, 2020

Bravo! Oh man, the "RSA Quest" was the most amazing thing ever! I can't even believe it worked out. And ended with a nod to one of my favorite authors!

This course was one of the most challenging, and at the same time rewarding courses I've done on Coursera. I absolutely love learning from these instructors. Their explanations are so methodical and complete that you really get a good understanding of not only the facts they assert, but the "why" and "how" beneath it. Thank you!

By Guo F

Apr 11, 2021

Wow! I'd say this is the very best course in this specialization! Although other courses are good too, I'd say this course explains things very clearly and rigorously, which is definitely needed to be so because of the topic involved. Kudos to the assignments, very interesting! Something I found out to be frustrating is, if I paused this course for a week or so, the proofs become obscure to me. I definitely need to review more often!


May 28, 2020

Highly recommended. Initially, the course seems to be a bit slow-paced but later you will understand that it was all necessary to build the foundation. The material is very good especially the exercises. The last portion teaches you RSA encryption and its prospective attacks. Overall the course was very well structured and intuitive, it made me think and apply the concepts taught.

By Artem B

Sep 5, 2021

I enjoyed the course from the beginning to the end. The material is well structured and presented. While the code assignments were not very challenging, I've got the main point: it's tough to implement encryption properly, and it's rather easy to crack it when it's done inaccurately enough. Definitely recommend the course as an introduction to cryptography.

By Agung A P

Jul 7, 2020

Alhamdulillah. Finally, I can pass this course, although not perfectly 100%, but I really proud of my self. Thanks to all lecturers in this course. I've got a lot of knowledge so far, especially in Number Theory. For cryptography subject, that's so hard. Not every people can solved it perfectly since it need a lot of creativity and logic.

By 储忻

Jun 20, 2021

The course material is very good. The exercise is very well prepared, especially the RSA quest in the end. Although the lecture in Week 3 and 4 seems a little bit fast, it's reasonable considering the amount and complexity of the knowledge that needs to be covered in such a short amount of time. I highly recommended this course.

By Deleted A

Jun 25, 2020

My only critique to this course are the final two quizzes of week 4. The very final quiz relies on you having successfully completed most of the penultimate quiz and is more of a "copy and paste" session. The RSA part (week 4) of this course had not been covered at my University and was very interesting.

By Iftakhar U

Jul 20, 2020

Alhamdulillah. I have learnt many things from this course. Thanks the three course instructor for taking this course. Most interesting things of the course for me was The end RSA Quest quiz. Again, Thanks coursera.

By Tejasvi V

Feb 5, 2021

Thank you! enjoyed learning number theory, understood new concepts of modular programming, how public key -private key works and the basis of rsa algorithm.


Apr 8, 2021

Excellent course to learn number theory and building blocks of cryptography. Excellent instructors make such topics easy to understand and not boring.

By Rajarshi D

Sep 18, 2020

Excellent material and teachers.

Specifically, the course contents of week 4 : the RSA quiz and the RSA quest quiz material is outstanding! Kudos!

By Aswani K C

Nov 30, 2020

Excellent course to learn number theory principles and relate them to asymmetric cryptosystems. The course is highly rigorous and challenging.

By Deepjyoti H P

Jul 30, 2020

This course was amazing! Got a good, but brief insight into the basics of cryptography. The examples at the end of the course were great!

By Perumali S

Jun 14, 2020

Its a good course to the beginers of cryptography.If you want to join you should know basic number theory and computer language python.

By Hepta M K

Aug 27, 2020

This course introduces one into the world of cryptograghy and was very interesting especially the RSA Quest.