CS255: Introduction to Cryptography

Introduction to Cryptography

Winter 2021

Cryptography is an indispensable tool for protecting information in computer systems. This course explains the inner workings of cryptographic primitives and how to use them correctly.


Course syllabus (and readings)
Course overview (grading, textbooks, coursework, exams)
Lectures: Monday, Wednesday, 2:30-3:50pm, online
Sections: Friday, 4:30-5:20pm, online
Questions for CAs: cs255ta@cs.stanford.edu or use Ed Discussion
Videos: cs255 online   (for video lectures and slides covering the material in class)

Final Exam

Due to remote learning, the final exam is entirely online.

The exam is due on 3/17 at 1pm PT. Please use gradescope to submit your answers. Because of university requirements, we cannot give extensions on the final exam.

Previous final exams:

2019.pdf ,   2018.pdf ,   2017.pdf ,   2016.pdf ,   2015.pdf ,   2014.pdf ,   2013.pdf ,   2012.pdf ,   2011.pdf ,   2010.pdf.


All homework submission is to be done via Gradescope. Please use course code V88N2K to sign up. Note that Gradescope requires that the solution to every problem start on a new page.

Homework #0:   [html]
Due: Jan. 20
Homework #1:   [pdf]
Due: Feb. 1
Homework #2:   [pdf]
Due: Feb. 17
Homework #3:   [pdf]
Due: Mar. 15


Project #1 (password manager):   pdf   starter code
Due: Mon., Feb. 8, 11:59pm
Project #2 (chat client):   pdf   starter code
Due: Mon., March 1, 11:59pm



  • Basic number theory fact sheet I, primes:   [pdf]
  • Basic number theory fact sheet II, composites:   [pdf]