Spring 2026
Barnard College
Instructor: Prof. Eysa Lee
Lectures: Mon/Wed 1:10pm-2:25pm, Location TBD
Office Hours: Wednesday 3-5p, Milstein 512
This course is an introduction to modern cryptography, focusing on the complexity-theoretic foundations of secure computation and communication in adversarial environments, precise definitions, and provably secure protocols. Topics include private and public key encryption schemes, digital signatures, authentication, pseudorandom generators and functions, one-way functions, trapdoor functions, number theory and computational hardness, identification and zero knowledge protocols.
The recommended textbooks for this course are "Introduction to Modern Cryptography" by Jonathan Katz and Yehuda Lindell and "The Joy of Cryptography" by Mike Rosulek. There will not be any assignments or assigned readings from the text, but they are useful references to assist in understanding the lectures.
Required: COMS W3203 (Discrete Mathematics) or equivalent
Recommended: COMS W3261 (Computer Science Theory)
Students are expected to be comfortable with discrete math, probability, Big-O notation, and basic reasoning about algorithms (such as correctness and runtime). Students will be expected to understand and write formal definitions and proofs.
While not required, it is helpful for students to have a background in CS theory, probability theory, and basic number theory. These topics will be briefly covered in the class as needed.
This course involves problem sets, a written midterm exam, and written final exam. Assignments are weighted as follows:
Every student must individually write and submit solutions to the homework problems assigned. Students are encouraged to discuss problems with one another and work toward solutions in small groups of their choosing. Students must include a written acknowledgment in their homework submissions if problems were discussed and with whom. The point of homework discussions is to help you understand the material: it is not acceptable to simply swap solutions, and every student should be able to orally explain every solution they submit. Looking at written homework solutions from the internet or other people is prohibited (this includes letting other students read your answers).
Assignments will incur a penalty of 10% of the total possible points per day it is late, up until 3 days. After 72 hours beyond the due date, no assignments will be accepted for credit. The lowest problem set grade will be dropped.
Students may request regrades for a week following the release of a grade, after which, regrades will be closed. Regrade requests are intended to address potential grading errors, not to serve as an avenue for negotiation.
The use of generative AI for anything related to assignments is prohibited in this class, at any stage. In particular, it is always forbidden to input any substantive portion of any assignment into any kind of AI resource. It is also always forbidden to incorporate any substantive portion of an AI resource's output into your answers, even if you paraphrase it or rewrite it in your own words. If you think that the instructor might refuse to perform a certain task for you or answer a certain question during office hours, then you should definitely not be asking an AI resource to perform the same task or answer the same question.
The tentative schedule below is subject to change. Please see the course schedule on the course homepage for the most up to date schedule.
| Week | Date | Topic | Assignment |
|---|---|---|---|
| 1 | 1/21 | Introduction | |
| 2 | 1/26 | Perfect Secret, One-Time Pads and their Limitations | |
| 1/28 | Efficient Computation, Non-Uniformity, Computational Indistguishability | PS 1 Released | |
| 3 | 2/02 | PRGs | |
| 2/04 | PRGs, reductions, hybrid arguments | ||
| 4 | 2/09 | CPA Security | PS 1 Due PS 2 Released |
| 2/11 | PRFs, PRFs from PRGs | ||
| 5 | 2/16 | CPA-secure Encryption using PRFs | |
| 2/18 | Block ciphers and PRPs | ||
| 6 | 2/23 | CCA Security and Padding Oracle Attacks | PS 2 Due PS 3 Released |
| 2/25 | OWFs | ||
| 7 | 3/02 | MACs, Authenticated encryption | |
| 3/04 | Hash functions | ||
| 8 | 3/09 | Hash functions | PS 3 Due |
| 3/11 | Midterm | ||
| - | Spring Recess | ||
| 9 | 3/23 | Basic number theory | PS 4 Released |
| 3/25 | Diffie-Hellman Key Exchange | ||
| 10 | 3/30 | Public Key Encryption | |
| 4/01 | Factoring, RSA | ||
| 11 | 4/06 | CCA Security, KEM | PS 4 Due PS 5 Released |
| 4/08 | Digital Signatures | ||
| 12 | 4/13 | Identification Schemes | |
| 4/15 | DSA, PKI | ||
| 13 | 4/20 | Zero-Knowledge Proofs | PS 5 Due PS 6 Released |
| 4/22 | Multiparty Computation | ||
| 14 | 4/27 | Secure Messaging | |
| 4/29 | Quantum Cryptography | ||
| 15 | 5/04 | Post-Quantum Cryptography | PS 6 Due |
| - | TBA | Final Exam |
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We, the students of Barnard College, resolve to uphold the honor of the College by engaging with integrity in all of our academic pursuits. We affirm that academic integrity is the honorable creation and presentation of our own work. We acknowledge that it is our responsibility to seek clarification of proper forms of collaboration and use of academic resources in all assignments or exams. We consider academic integrity to include the proper use and care for all print, electronic, or other academic resources. We will respect the rights of others to engage in pursuit of learning in order to uphold our commitment to honor. We pledge to do all that is in our power to create a spirit of honesty and honor for its own sake.
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