The apparatus for generating a secure substitution-box immune to differential and linear cryptanalysises comprises a preprocessor for exchanging a location by the unit of bit while passing the input of 64 bits data to be protected; a parity checker for obtaining 56 bits key information...http://www.google.co.uk/patents/US5796837?utm_source=gb-gplus-sharePatent US5796837 - Apparatus and method for generating a secure substitution-box immune to cryptanalyses 
