CS 7111: Topics in Cryptography (Jan-May 2026)

Instructor: Ashrujit Ghoshal, ashrujit@cse
Time and Location: Wednesdays (3:30-4:45 pm) and Fridays (2-3:15 pm) at CS 34
Office Hours: Wednesdays (5-6 pm) at SSB 206

General Description

This course will focus on two cryptographic tools: Zero-knowledge proofs (ZKPs) and Private Information Retrieval (PIR). ZKPs are used to prove a statement to a verifier, without revealing anything more beyond the veracity of this statement. We will focus particularly on succinct non-interactive ZKPs that are practically appealing for their efficiency. PIR is a tool that allows a client to access entries of databases stored on one or more non-colluding servers, without the servers gaining any information about what was accessed. We will focus on the recent progress on preprocessing PIR that has taken strides towards making practical, scalable PIR a reality.

These tools are cornerstones in the design of privacy-preserving systems, e.g., in solutions for private browsing, private contact discovery, anonymous credentials etc.

Covered Materials (tentative). Zero Knowledge Proofs: definitions, the simulation paradigm, NIZKs and the Fiat-Shamir Transform, SNARKs: modern constructions, Private Information Retreival: definition, two-server information theoretic constructions, Distributed Point Functions, Single-server PIR with preprocessing, Doubly Efficient PIR.

Required Background. The class will be self-contained with the only expectation being students being able to understand mathematical definitions and proofs, and write simple ones.

Grading

There will be two take-home assignments and students are expected to present a paper (in groups) from a list of assigned papers during the last two weeks of classes. Due to somewhat unpredictable enrollment numbers, the exact implementation of this will be finalized during the first week of class. There will also be a midterm and a final, and a class participation component that will decide the final grade.

• Assignments: 10%
• Project writeup: 15%
• Project presentation: 25%
• Midterm: 20%
• Final: 25%
• Class Participation: 5%

Resources

There is no mandatory textbook. Slides and reading materials will be posted online. These are some good reference materials (books and courses) for the topics of the class.

• Proofs, Argument and Zero-Knowledge, a textbook by Justin Thaler (Good reference for ZKP)
• Cryptography meets Algorithms, a course by Elaine Shi (The first part of Elaine’s course is a good reference for PIR)

Finally, these are some good general cryptography textbooks.

• A Graduate Course in Applied Cryptography by Dan Boneh and Victor Shoup
• Introduction to Modern Cryptography by Jonathan Katz and Yehuda Lindell
• The Joy of Cryptography by Mike Rosulek

Schedule

The schedule will be expanded and refined as we proceed through the semester.

Academic Integrity

Academic integrity is central to this course. For assignments, you are permitted to work with one partner and submit a single joint solution. The work you submit must reflect the combined independent effort of your pair. It must be written in your own words, and you must clearly acknowledge any external sources or help received.

While you may discuss high-level concepts or approaches with students outside of your partnership, the work you submit cannot be copied, closely paraphrased, or derived from another group’s solution. If you do discuss the assignment with others, please include a brief note listing who you spoke with and the nature of that discussion.

The use of LLMs to generate solutions is strictly prohibited. If you are ever unsure about what is permitted, do not assume. Please ask the instructor or course staff for clarification. Any violation of these rules will result in a failing grade for the course and a report to the disciplinary committee.