# Cryptography

**CS499/ CS587: Cryptography**

**George Mason University, Computer Science, Spring 2021**

**Instructor: **Prof. Foteini Baldimtsi (foteini@gmu.edu)

**Office Hours: **Monday and Wednesday 2:45PM-3:45PM, Online on Zoom

**Lectures: **Monday and Wednesday 1:30PM-2:45PM, Online Synchronous

### Course Description

The course will provide an introduction to modern cryptography. We will cover many practical topics, such as how to correctly use block ciphers and hash functions for the most common tasks: encryption and message authentication, the differences between public key cryptography and symmetric key cryptography, and a few ways to build public key encryption and signatures. We will learn about how to properly define security, and how to prove that our constructions are secure. In addition, and if time permits, we will also cover some recent topics in cryptography, such as the use of blockchains for crypto currencies (i.e. Bitcoin), zero-knowledge proofs of knowledge, and searching on encrypted databases.

* Objectives: *The main objectives are to convey the importance of

*provable*security, to teach students how to use cryptographic tools in a way that is provably secure, to provide students with the ability to decide whether a protocol is secure, and to demonstrate the range of what can be achieved with provable security.

**Course Outcomes: ** Students taking this class will be able to: (a) understand the security properties achieved by common cryptographic mechanisms such as encryption or digital signatures, (b) be familiar with a number of cryptographic protocols (toolbox) available to solve a variety of problems, (c) gain some experience on how cryptographic tools are used to secure modern systems such as cryptocurrencies.

**Prerequisites: **There is not a hard prerequisite for this course but being familiar with material taught on CS 330 is very helpful. Although we will learn about practical topics in cryptography, students will need some level of mathematical maturity, i.e. being familiar with concepts in probability theory (computation of expectation, conditional probability etc) and complexity theory (Turing machines, NP-completeness etc) would be helpful for an easier understanding of formal security definitions and proofs. This is __not a course__ about computer hacking or computer security.

### Logistics

* Lectures: *The course will meet virtually, using Zoom. You will need to register one time before you can attend any of the meetings. You can find the meeting link through Blackboard: click on Tools, then Zoom. The password for every meeting will be the same, and will be posted on the course piazza board.

**Office Hours: **Office hours will be held the same way as lectures.

**Webcams: **I

**strongly**encourage the use of webcams, it makes the class far more enjoyable for everyone and helps me get a better idea of your understanding of the class material.

**Lecture Videos: **All lectures will be recorded and posted on Blackboard after class.

**Communications: **We will use Piazza to communicate with you. If you have a question about the course you should: (a) Come to office hours, OR (b) Post on Piazza. We have already set up different tags for HW problems and lectures. Please __don't use private posts/emails __to ask technical questions. The rest of the class is probably also interested in your question, so make it public!

### Course Requirements

**Text Book:** Katz and Lindell. *Introduction to modern cryptography*, Second Edition. **(Required). **

There will also be additional readings for each class (available online for free) listed below.

- Cryptography Primitives and Protocols, Aggelos Kiayias
- The Joy of Cryptography, Mike Rosulek
- A course on Cryptography, Rafael Pass & abhi shelat
- Cryptography, an introduction, Nigel Smart
- Introduction to Modern Cryptography, Mihir Bellare & Phil Rogaway

**Grading**

- Assignments: 35% (10 assignments lowest grade dropped)
- Quizzes:
- Midterm: 25%
- Final: 30%

**Assignment Submission and Late Policy: **Homework questions will be posted on Blackboard/Gradescope and solutions__ have to__ be submitted through Gradescope right before class on Wednesday. No credit will be given to late submissions but the lowest grade will be dropped. To be fair with everyone in class __no exception__ will be made to the rule above.

**Graduate Students (CS 587): **Graduate students will be given an extra HW problem to solve in most of the assignments. They will also have to solve an extra problem in both midterm and final and independently study some additional material.

**Honor code:** All students must adhere to the GMU Honor Code. You can discuss lecture material with other students in class but you have to work on the assignments alone. More specifically: (1) You must work on the homework problems and write your solutions completely on your own, without looking at other people’s write-ups. (2) You are welcome to use any textbooks, online sources, blogs, research papers, Wikipedia, etc to better understand a notion covered in class or in a homework question. If you do so you __have to__ properly cited it in any submitted work. Failure to do this is plagiarism and is serious violation of the GMU Honor Code and basic scientific ethics, and will not be tolerated. Note that it is not OK to search for solutions to HW problems online.