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. However, note that this course is not a course on cryptoanalysis.

Lectures:

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

Recitations (Tutorien):

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

Note: The recitations start in the third 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.

- 100% exam

Active participation requires successful completion of homework assignments and projects and is graded on a pass / no pass basis. At least 50% of the cumulative score is required to pass.

The exam will take place on Wednesday, February 20th, from 11am to 1pm in Arnimallee 6, room SR 025/026.

Dr. Jänicke holds the position of Chief Technology Officer at Innominate Security Technologies. He is a renowned security expert and contributed to several Open Source projects. Among other things, he developed the Postfix/TLS protocol extension for encrypted mail transfer (RFC2487). He is also a member of the OpenSSL Project development team and will speak on the SSL protocol and its OpenSSL implementation.

Below are the homework assignments. Each assignment is given on a Monday, and is discussed on the Monday two weeks later.

- Homework 1 is discussed on November 19th, 2012
- Homework 2 is discussed on December 3rd, 2012
- Homework 3 is due on January 7th in writing (LaTeX), 2013

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

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

Topics:

- Handling variable-length messages
- Indistinguishable multiple encryptions in the presence of an eavesdropper
- Probabilistic encryption
- Chosen plaintext attacks

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

Topics:

- Pseudorandom functions
- Pseudorandom permutations
- Indistinguishable encryptions under a chosen plaintext attack
- 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

Read: chap. 4 of [2]

Topics:

- Constructions of variable-length MAC
- CBC-MAC for fixed-length and variable-length messages

Read: chap. 4 of [2]

Topics:

- Collision resistant hash functions
- Birthday attacks
- Merkle-Damgard transform

Read: chap. 4 of [2]

This lecture will be given on Monday December 17th in the tutorial

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:

- Mathematical background for public-key cryptography

Read: chap. 7 of [2]

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

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], [5]

Topics:

- Homomorphic encryption
- The Paillier encryption scheme

Read: sect. 11.3 of [2], [6], [7]

Topics: Taming the complexity of security proofs

- Sequences of games

Read: [8]

Topics:

- Introduction to cryptographic protocols
- Needham Schroeder
- Key management
- Key distribution centers
- Public key directories
- Public Key Infrastructure
- Web of Trust
- Identity

Read: [9], [10], [11], [12], [13]

Topics: TBD

This lecture will be held on Thursday, the exam will take place on Wednesday February 20th.

Topics: Guest lecture by Lutz Jänicke, OpenSSL development team

- The SSL protocol and the OpenSSL implementation

Read: [14]

- 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.
- 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.
- Victor Shoup. Sequences of Games: A Tool for Taming Complexity in Security Proofs. Cryptology ePrint Archive, 2004.
- Martin Abadi and Roger Needham. Prudent Engineering Practice for Cryptographic Protocols. Digital Equipment Corporation, November 1995.
- 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.
- Moxie Marlinspike. Null Prefix Attacks against SSL/TLS Certificates. Published online.
- Moxie Marlinspike. Defeating OCSP With the Character '3'. Published online.
- T. Dierks, E. Rescorla. The Transport Layer Security (TLS) Protocol Version 1.2. RFC 5246, IETF, 2010.