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Prof. dr. ir. Bart Preneel Bart Preneel

Professor Bart Preneel of KU Leuven heads the COSIC (COmputer Security and Industrial Cryptography) research group. His main research area is information security with a focus on cryptographic algorithms and protocols as well as their applications to both computer and network security, and mobile communications.

He teaches cryptology, network security and coding theory at the KU Leuven and was visiting professor at the Ruhr Universitaet Bochum (Germany), the T.U.Graz (Austria), the University of Bergen (Norway), and the Universiteit Gent (Belgium). In '93-'94 he was a research fellow at the University of California at Berkeley. He has taught intensive courses around the world.

He undertakes industrial consulting (Mastercard International, S.W.I.F.T., Proton World International,...), and participates in the work of ISO/IEC JTC1/SC27/WG2.

Professor Preneel is Vice President of the International Association for Cryptologic Research (IACR) and co-founder and chairman of LSEC vzw (Leuven Security Excellence Consortium).


Cryptographic algorithms

Learning objectives

  • understand the fundamental concepts of cryptology;
  • distinguish the different types of cryptographic algorithms;
  • appreciate how cryptographic algorithms can provide
    • confidentiality,
    • data authentication.


Stream ciphers, block ciphers and hash functions are the three classical types of symmetric algorithms.

A stream cipher generates a keystream of random bits which are exclusive-or'ed with the plaintext. Stream ciphers are often used to provide confidentiality for real-time traffic, such as GSM and Bluetooth.

Block ciphers repeat simple substitution and transposition operations many times on fixed size blocks. The Data Encryption Standard (DES) has been widely used in banking, but is superseded by triple-DES and AES.

Hash functions accept input strings of arbitrary length and produce fixed-length output. A Manipulation Detection Code (MDC) affords integrity protection. Given an output of an MDC, it is infeasible to find the corresponding input and it should be difficult to find colliding inputs. Practical examples are SHA-1, SHA-256 and RIPEMD-160.

A Message Authentication Code (MAC) is a hash function with a secret key that provides data origin authentication. Practical examples are CBC-MAC, based on triple-DES and AES block ciphers.


Solvay Brussels School of Economics and Management Katholieke Universiteit Leuven

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