Cryptanalysis (SS 2022)

Content

Cryptanalytic attacks define the security of cryptographic algorithms, and understanding them is crucial to understand cryptographic design. This lecture aims to give you some in-depth knowledge of several recent state-of-the-art topics in cryptography, with a focus on cryptanalysis:

• Classic and quantum algorithms for factoring and discrete log
• Cryptanalysis of block ciphers (differential, linear, algebraic)
• Cryptanalysis of hash functions and stream ciphers
• Lattices and continued fractions in cryptanalysis

In the exercises, you will implement some of these attacks to solve cryptanalytic challenges. In the seminar, additional selected topics may be presented by participants -- see below for a list of suggested topics.

Material

Lecture and Seminar

Date	Who	Lecture (16:00-17:30 in HS i1)	Video (2021)
03.03.2022	ME	L1 – Factoring and Continued Fractions	YouTube
10.03.2022	ME	L2 – Discrete Logarithm	YouTube
17.03.2022	MS	L3 – Quantum Cryptanalysis	YouTube
24.03.2022	RW	L4 – Lattices	YouTube
31.03.2022	MS	L5 – TLS security & Protocol Attacks	YouTube
07.04.2022	MN	L6 – Differential Cryptanalysis	YouTube
28.04.2022	ME	L7 – Linear Cryptanalysis	YouTube
05.05.2022	ME	L8 – Advanced Differential Attacks	YouTube
12.05.2022	MS	L9 – Sponges & Stream Ciphers	YouTube
19.05.2022	MS	LA – Algebraic Attacks	YouTube
02.06.2022	you	Seminars (T1, T2, T6)
09.06.2022	you	Seminars (T7, T8)
23.06.2022		Seminars
30.06.2022	you	Exam

We have two guest talks this year by Roman Walch (L4) and Marcel Nageler (L6). All videos from SS 2021 are listed in the YouTube playlist.

Exercises

Date	Topic	Where
17.03.2022	Team registration deadline	TeachCenter
17.03.2022	T1 – Asymmetric Cryptanalysis	After L3 in HS i1
28.04.2022	T1 – Submission deadline (23:59)	git
05.05.2022	T1 – Assignment interviews (individual slots)	Office
05.05.2022	T2 – Symmetric Cryptanalysis	After L8 in HS i1
09.06.2022	T2 – Submission deadline (23:59)	git
15.06.2022	T2 – Assignment interviews (individual slots)	Office
23.06.2022	T2 – Assignment interviews (individual slots)	Office

Administrative Information

Exercises (KU)

In the exercises, you implement cryptanalysis techniques from the lecture in teams of 2. To get a grade, you submit your implementations for 2 assignments, which we will discuss with you in a final interview ("Abgabegespräch"). Use TeachCenter to register your team and git for your submissions. We usually won't need the 16:30–17:15 KU timeslots (except for question times and seminar presentations).

Lecture exams and seminar talks (VO)

There are 2 ways to get a grade for the VO:

• Exam mode: Write exam at the end of the term or take an oral exam later. Register for an exam date in TUGRAZonline or contact us if none is available.
• Seminar mode: Participate actively in KU+VO and give a seminar presentation in one of the last lectures (30 minutes) accompanied by a short report (10 pages) in your team, for example on
  • Block Ciphers: Division Property | MitM and Biclique Attacks | Boomerang Attacks | ...
  • Hash Functions: Rebound Attack | Cryptanalytic Exploits (MD5 Certificates etc.) | ...
  • Authenticated Encryption: Security Proofs and Robustness | ...
  • RSA: (In)Security in Practice | Secure Key Generation | ...
  • Post-Quantum: Coding-based Cryptography | Lattices and Learning with errors | ...
  • Implementation Security: Secure Masking | Statistical Ineffective Fault Attacks | ...

COVID-19 Info

All lectures and exercises are conducted in presence this year. From the virtual lecture in SS 2021, recordings are available on Youtube. Exercise interviews and question hours will be conducted either in presence or on Discord, where you can also ask written questions at any time. For the optional seminar talk, you will have the choice between online and live presentations if conditions permit. The alternative is a written on-campus lecture exam.

Literature

The lecture slides are reasonably self-contained, but often briefly phrased. If you prefer full-text resources, you may find some of the following books interesting:

• The Block Cipher Companion, by L.R. Knudsen and M.J.B. Robshaw
• An Introduction to Mathematical Cryptography, by J. Hoffstein, J. Pipher, and J.H. Silverman

Lecturers