Prof. Dr.-Ing. Volker Roth

This course gives a modern introduction to cryptography and cryptographic key management, followed by an introduction to cryptographic protocols and their applications in distributed systems security. Mathematical background is developed to the degree reasonable in an introductory class. In addition to the mathematical underpinnings of cryptographic primitives the course also touches on the importance of implementation for a secure system.

Lectures:

- Tuesdays, 16h - 18h, T9/005
- Thursdays, 12h - 14h, T9/005

Recitations (Tutorien):

- Mondays, 16h - 18h, T9/051

Note: The recitations commence in the second week of the semester.

The grade will be computed as a weighted sum as shown below. Passing the exam is necessary to pass the course.

- 80% exam
- 20% project

Students will be admitted to the exam if they pass the mid-term exam or they earn at least 50% of the points in n-2 home work assignments (where n is the overall number of assignments).

Below are the homework assignments. Each assignment is given on a Monday, and is due on the Monday two weeks later. You can turn in your assignments at the recitation or at Fabeckstraße 15 before the recitation.

- Homework 1 is due on November 15, 2010
- Homework 2 is due on November 29, 2010
- Homework 3 is due on December 13, 2010
- Homework 4 is due on December 17, 2010

Topics:

- Welcome and administrativa
- Private key encryption
- Historic ciphers and their cryptanalysis
- Principles of modern cryptography

Read: sect. 7.3 of [1]

Topics:

- Perfectly-secret encryption
- Adversarial indistinguishability
- Vernam cipher
- Limitations of perfectly secure encryption

Read: chap. 2 of [2]

Topics:

- Shannon's Theorem and its proof
- Introduction to computational security

Read: chap. 2 of [2]

Topic:

- Relaxations of perfect secrecy
- Efficient computation and negligible success probability
- Proofs by reduction
- Pseudorandomness and pseudorandom generators
- Indistinguishable encryptions in the presence of an eavesdropper
- Handling variable-length messages

Read: chap. 3 of [2], the anecdote in [3]

Topics:

- Indistinguishable multiple encryptions in the presence of an eavesdropper
- Probabilistic encryption
- Chosen plaintext attacks
- Psedurorandom functions
- Indistinguishable encryptions under a chosen plaintext attack

Read: chap. 3 of [2], [4]

Topics:

- Pseudorandom permutations
- Block ciphers and operation modes

Read: chap. 3 of [2]

Topics:

- Counter mode
- Chosen cipher text attacks and non-malleability

Read: chap. 3 of [2]

Topics:

- Encryption versus message authentication
- Message authentication codes
- Existential unforgeability under adaptive-chosen message attacks
- Replay attacks
- Constructions of fixed-length MAC
- Constructions of variable-length MAC

Read: chap. 4 of [2]

Topics:

- CBC-MAC for fixed-length and variable-length messages
- Collision resistant hash functions
- Birthday attacks
- Merkle-Damgard transform

Read: chap. 4 of [2]

Topics:

- Encryption secure against chosen ciphertext attacks

Read: chap. 4 of [2]

Topics:

- Practical constructions of pseudorandom permutations
- Substitution permutation networks
- Feistel networks
- DES and AES
- 2-DES, meet-in-the-middle attacks, 3-DES

Read: chap. 5 of [2]

Topics:

- Introduction to number theory
- Primes and divisibility
- Bezou's Lemma and the extended Euclidean algorithm
- Modular arithmetic
- Cyclic groups

Read: chap. 7 of [2], [5]

Topics:

- The factoring assumption
- The RSA assumption
- The discrete logarithm assumption
- The DH assumptions
- Factoring and one-way functions
- Discrete logarithms and collision resistant hash functions

Read: chap. 7 of [2]

Topics:

- From private key management to public key cryptography
- Diffie-Hellman key exchange

Read: chap. 9 of [2]

Topics:

- Public key encryption
- Public key encryption and indistinguishable encryptions

Read: chap. 10 of [2]

Topics:

- Hybrid encryptions secure against chosen plaintext atacks

Read: chap. 10 of [2]

Topics:

- Attacks on text book RSA
- Implementation issues
- ElGamal encryption
- Chosen ciphertext attacks against RSA and ElGamal

Read: chap. 10 of [2]

Topics:

- Digital signature schemes
- The hash and sign paradigm

Read: chap. 12 of [2]

Topics:

- Security in the random oracle model

Read: chap. 13 of [2], [6]

Topics:

- Homomorphic encryption
- The Paillier encryption scheme

Read: sect. 11.3 of [2], [7], [8]

Topics:

- Key management
- Key distribution centers
- Public key directories
- Public Key Infrastructure
- Web of Trust
- Identity

Read: [9], [10]

Topics:

- Introduction to cryptographic protocols
- Needham Schroeder
- Kerberos

Read: [11]

Topics:

- Secure Sockets Layer
- Secure Shell
- Short authenticated strings

Read: [12], [13], [14], [15], [16]

Topics:

- Wide area routing security
- Secure BGP
- Onion routing

Topics:

- Bit committment
- Flipping coins over the telephone

Topics:

- Oblivious transfer
- Playing poker over the telephone

Guest speaker: TBD

Topics:

- Dining cryptographers
- Secret sharing

Guest speaker: **Dr. Kim Nguyen**, *Bundesdruckerei GmbH*

Topic:

- Introduction to elliptic curves
- Groups based on elliptic curves
- Elliptic curve cryptography
- Applications

Class project presentations

Final exam

- Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone. Handbook of Applied Cryptography. CRC Press, 2001.
- Jonathan Katz, Yehuda Lindell. Introduction to Modern Cryptography. Chapman & Hall/CRC, 2008.
- R. Morris and K. Thompson. Password security: a case history. Commun. ACM 22, 11 (Nov. 1979), 594-597.
- Hongjun Wu, The Misuse of RC4 in Microsoft Word and Excel. IACR e-print number 007, 2005.
- Victor Shoup. A Computational Introduction to Number Theory and Algebra. Cambridge University Press, 2008.
- Mihir Bellare and Phillip Rogaway. Random Oracles are practical: a paradigm for designing efficient protocols. Proc. ACM Computer and Communications Security, November 1993.
- Caroline Fontaine and Fabien Galand. A Survey of Homomorphic Encryption for Nonspecialists. EURASIP Journal on Information Security, October 2007.
- Castelluccia, C., Chan, A. C., Mykletun, E., and Tsudik, G. 2009. Efficient and provably secure aggregation of encrypted data in wireless sensor networks. ACM Trans. Sen. Netw. 5, 3 (May. 2009), 1-36.
- Loren M. Kohnfelder. Towards a practical public-key cryptosystem. B.Sc. thesis, MIT, May 1978.
- Carl M. Ellison. Establishing Identity Without Certification Authorities. In Proc. USENIX Security Symposium, July 1996.
- Martin Abadi and Roger Needham. Prudent Engineering Practice for Cryptographic Protocols. Digital Equipment Corporation, November 1995.
- D. Brumley and D. Boneh. Remote timing attacks are practical. In Proc. 12th Usenix Security Symposium, 2003.
- Paul C. Kocher. Timing Attacks on Implementations of Diffie-Hellman, RSA, DSS, and Other Systems. In Proc. CRYPTO (1996). Lecture Notes In Computer Science, vol. 1109. Springer-Verlag, London, 104-113.
- T. Dierks and C. Allen. The TLS Protocol Version 1.0. Internet Engineering Task Force Request for Comments 2246, January 1999.
- Moxie Marlinspike. Null Prefix Attacks against SSL/TLS Certificates. Published online.
- Moxie Marlinspike. Defeating OCSP With the Character '3'. Published online.