CSA E0 235 : Cryptography
(August - December 2025)

Instructor: Arpita Patra (Email: arpita AT iisc DOT ac DOT in)

Timings: 11:30 am - 1:00 pm on Tuesday and Thursday.

Venue: CSA 112

Study Materials

• (KL) “Introduction to Modern Cryptography” by Jonathan Katz and Yehuda Lindell, second edition 2014, CRC Press.
• (Gol) “Foundations of Cryptography” by Oded Goldreich.
• (BS) “A Graduate Course in Applied Cryptography” by Dan Boneh and Victor Shoup. [Link]
• (Sti) “Cryptography: Theory and Practice” by Douglas R. Stinson, third edition 2003, CRC.
  

Course Description

• One way Functions (Permutations), Hard-core Predicates, Pseudo-random Generators, (Strong) Pseudo-random Functions (Permutations).
• Secret Key Encryptions (SKE): Various security notions such as Perfect Security, Semantic Security, Indistinguishability based Security, CPA Security, CCA Security, Constructions, Block Cipher Mode of Operations.
• Message Authentication Codes (MAC): Various Security notions such as CMA Security, (weak/strong) CMVA security, Domain Extension, CBC-MAC.
• Advanced Encryption Schemes: Authenticated Encryptions.
• Introduction to Secure Computation (Yao’s 2PC protocol and Circuit Garbling).
• Number Theory: Preliminaries, Modular arithmetic, elementary group theory, CRT, hardness assumptions.
• Trapdoor permutations: definitions, construction based on factoring, CR Hash functions based on number-theoretic assumptions.
• Public-key encryption: Implications of Semantic Security, Textbook RSA, Padded RSA, ElGamal, CCA secure public key encryption.
• Digital signatures: definitions, hash-and-sign paradigm, Lamport’s scheme, RSA signatures.
• Protocols: Identification protocols, proving properties in zero knowledge, non-interactive proof systems and applications.

Grading

• Two midterm exam (40 points)
• One reading project (20 points)
• Endterm exam (40 points)
• Cryptic Bonus Problem (10 points)
• Note: A student can score a maximum of 100 points.

Announcements

• The second midterm will be held on Friday, 17th October 2025, 09:30 am - 12:00 pm in CSA 112.
• The first midterm will be held on Friday, 12th September 2025, 11:00 am - 01:00 pm in CSA 112.
• Tutorial sessions will be held on every Friday, 11:30 am - 01:00 pm in CSA 112.

Academic Integrity

• Improper academic behaviour: Copying during exams, copying of homework assignments, term papers or manuscripts, verbatim or paraphrased. Allowing or facilitating copying, or writing a report or exam for someone else. Using unauthorized material and collaborating when not authorized. [Details]
  
• Action: In the case of a violation of the academic integrity, the student’s ID will be reported to the Office of Career Counselling and Placement (OCCaP).

Lectures

Tutorials

Reading Projects

• 1. Communication Complexity of Secure Computation   Reference: [Paper].
• 2. Advanced Encryption Standard (AES)   Reference: KL book.
• 3. CTR Mode + Proof   Reference: KL book.
• 4. PRF to SPRF (Luby Rackoff)   Reference: KL book.
• 5. Secret Sharing Made Short   Reference: [Paper].
• 6. GMW Protocol   Reference: [Paper].
• 7. Information-Theoritic MACs   Referenec: KL book.
• 8. Constructing CRHF from DL Problem   Reference: KL book.
• 9. Constructing from DDH Problem   Reference: [Paper].
• 10. Pederson Commitment Scheme   Reference: [Paper].

Cryptic Bonus Problems

• 1. Indian connection to Cryptography: Find some developments in cryptography done in India from the prehistoric times to classical period but excluding modern cryptography.
• 2. Decipherment of Indus Script: Critcize [this paper] based on the methods that have been used for the deciphermnent and argue why you think it may not work or provide arguments in support of the methods used and describe how a successful decipherment was achieved.