There were some doubts about the cryptographical strength of the DES algorithm since it was published. But a new stronger algorithm can be developed from the DES by an appropriate improvement.
The purpose of this study is to present the design critetia for a new algorithm that can be used as a Korean Encryption Standard for computer security applications in commercal part.
The main part of this study is the following ares; first, this thesis verifies defects of the DES in terms of cryptoanalysis. Two major defects are small key size and trapdoor which may be built in S-Box. Second, this thesis verify strong structure of the DES algorithm through the analysis of adoptability of the MLE cryptoanalysis for the DES. Third, key dependent S-box algorithm is introduced, that easily enlarges key size and prohibits trapdoor cryptoanalysis.
