Design of Block Ciphers and Security Enhancement by Key Expansion

By Prof. Virendra Sule


This talk describes the project Design of a Block Cipher which was sponsored by the NCETIS, at IIT Bombay. The objective of the project was to develop a family of Block Cipher algorithms for use by Indian Govt. agencies. As per the policy followed by Govt. agencies in cipher algorithms it is mandatory that the algorithm should not be a published one. It is notoriously difficult and time consuming to design a completely new algorithm which is secure. On the other hand, Govt. agencies require a rapid production of such secure algorithms. Hence in this project it was decided to first create a family of designs which will be able to enhance the security of known and already in use algorithms. With such a motivation we first see a new method of variation of algorithms by key extension which makes a known algorithm more secure than before. Next a methodology for randomization of a cipher algorithm was utilized to produce a new block cipher family. The architecture of this new family of algorithms was developed and analyzed and is ready for Govt. agencies to adopt if any such agency is interested.


Prof. V.R.Sule completed Ph.D. in 1990 from IIT Bombay and has been on the faculty of Electrical Engineering at IIT Kanpur and later at IIT Bombay since then. He has published research work in Control and Systems theory and Cryptology which has received high citations. He has guided several doctoral students. He has advocated a new approach to Cryptanalysis of block and stream ciphers called “Symbolic Cryptanalysis”. Using this approach, he has shown breaking of the 80bit stream cipher Bivium in practical time and memory constraints without the brute force search. He has also developed a family of block cipher designs which have superior security properties and are simple for implementation. He is a free thinker and an avid reader of Theory of Evolution and Evolutionary approach to History advocated by Historian Harari.

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