Monday, May 21, 2012

Comparing the Coursera and Udacity Cryptography classes

Over the spring, I worked my way through two online cryptography classes:

Taking both classes was not a waste; the two presentations nicely complemented and reinforced each other, and in the end I felt that I learned a lot from each.

But there were both differences and similarities between the courses, which I found interesting.

Both formats are broadly the same:

  • Both classes are, roughly, upper-division undergraduate classes in modern cryptography, covering roughly the same material
  • Both classes are presented as video lectures, in the style of allowing you to view the virtual whiteboard that the lecturer is drawing on, while listening to the lecture.
  • Both classes augment the video lectures with quizzes, homework assignments, additional reading, and forums for students to gather and discuss the material

Some of the differences in the classes were mechanical:

  • The videos for the Boneh class were generally 12-20 minutes in length, each, while the videos for the Evans class were generally 1-3 minutes in length, each
  • The slides and quizzes for the Boneh class were typeset, and were supplemented by a certain amount of free-hand annotation, while the slides and quizzes for the Evans class were presented entirely in free-hand
  • The classes present the material in a different order
  • Although the materials used largely similar notation, there were notational differences (e.g., Boneh uses the terminology "public key/secret key" and the letters "p" and "s", where Evans generally uses the terminology "public key/private key" and the letters "u" and "r")

The most important differences, though, are a bit harder to describe.

I felt that the Boneh class was more theoretical, more rigorous, and more oriented around the mathematical aspects of cryptography. Boneh emphasized a fair amount of probability theory and number theory during the class, spent more time proving theorems during the videos, and used more structured techniques such as the probabilistic "adversary games" that I wrote about several weeks ago.

Meanwhile, I felt that the Evans class was more practical, more approachable, more intuitive, and more oriented around the applied aspects of cryptography. Evans uses many examples from real life, concentrates more on results and less on derivations, and presents the material in context of its use. Evans also spends a great deal more time discussing the history of cryptography research, with interesting illustrations of important milestones and events, pictures of the people and objects that have been part of the history of cryptography, and so forth.

In general, I was extremely impressed by both courses. The material was clear, accurate, relevant, well-presented, and thoroughly explained. A motivated student who approaches either of these courses with energy and time and commitment will reap significant rewards. After just a few months of serious study, I felt like I had substantially improved my knowledge of these areas, and felt both interested in and prepared to take my studies further.

I hope that this is the beginning of a widespread availability of educational materials of the finest quality on the Internet, and I hope that these courses both find the audience that they deserve.

Update: Professor John Regehr provides a look at the Udacity environment from the other side of the desk, describing his work preparing a class on Software Testing for Udacity

it became clear that designing good programming quizzes is one of the keys to turning lecture material into actual learning. Tight integration between listening and hacking is one of the reasons that online learning will — in some cases — end up being superior to sitting in class. So this became my main challenge: creating a sequence of programming quizzes that basically leads students through the material.


  1. Thank you! I was looking for unbiased comparison between Coursera & Udacity on the same course, and your article was the one.

    May I act greedy and ask for CS101 comparison if you have attended it through both platforms ?

    1. I'm afraid this is the only class I've taken at either site so far, so I don't have any guidance on the other classes yet. Let me know what you find out!

  2. Thanks for sharing. I just finished the first lesson/quiz/challenge of Prof. Evans' course at Udacity, and wholeheartedly recommend it so far.