Cryptography

The Snowden/NSA affair has made a wider audience aware that virtually all electronic communication and data exchange over the Internet can and will be intercepted. Especially with confidential data such as credit card information when shopping in an online shop, it is important that these do not fall into the wrong hands. Therefore, it is extremely important for modern communication that the following security problems are solved:

• My data should only be readable by the intended recipient.
• I want my data to arrive unaltered.
• I need to be sure that I am communicating with the right person (and not with a fake Amazon website, for example).

Cryptography does all this. The lecture provides an introduction to modern cryptography, i.e. to the theory and practice of (preferably) secure encryption of data. Basic cryptographic algorithms such as block encryption functions, key stream generators, one-way cryptographic functions, one-way functions and cryptographic hash functions are dealt with. As a first step, the treatment includes an analysis of the areas of application and threat scenarios from which, in addition to the ubiquitous demand for efficiency, the security-relevant design criteria for the corresponding cryptographic algorithms can be derived.

In addition to providing the mathematical, algorithmic and information-theoretical fundamentals necessary for understanding the material, various practical methods such as the Data Encryption Standard (DES) and the Advanced Encryption Standard (AES), the A5 algorithm of the GSM standard and the E0 algorithm of the Bluetooth standard are presented and evaluated.

The lecture slides and exercise sheets can be found in the ILIAS course Kryptographie I [VÜ] [1. PG] (FSS 2024).