Development of Block Ciphers

Prof. Virendra Sule

Project is centered on developing new block cipher algorithms, key extension for known cipher algorithms and Boolean methods for cryptanalysis of block and stream ciphers.

Following deliverables have been developed in this project.

– Methodology for extending the length of symmetric key of cipher algorithms. Tested for case study of AES-128 for extension by 64 bits. A hardware implementation of the block for key extension also developed. It is shown that extended AES satisfied much larger number of statistical tests than AES without extension. Cryptanalysis of extended key cipher proves that the cipher is not weakened by extension.

– A new methodology for block cipher algorithms which uses randomization of inputs and provides required computational security by using simple structures with random inputs. This methodology of using random inputs which are not exchanged like the symmetric key allows achieving computational security of the algorithm due to randomness of the input. Hence, the structure of the cipher algorithm is much easier for justification of security compared to non linear SP- networks used in block cipher design.

– Boolean cryptanalysis methodology for stream ciphers for key recovery using the output stream in realistic conditions. A case study of complete break of Bivium-80 bits cipher available for demonstration. This methodology is the most definite and general for key recovery of any stream cipher. The weakness of the cipher is evaluated by means of solving Boolean systems obtained from the model of the cipher.