The characteristics of cascade ciphers are analyzed and three strengthened techniques of block cipher: cipher cascade technique, multiple cipher technique and wipe technique, are discussed.

Taking light calcium carbonate as an example,in order to make its manufacturers understand the measures——how to enhance the product′s whiteness from theories to practice,this paper fully expatiated on various effecting factors of chemical whitening,process of chemical whitening,establishmen.

The techology conditions were analyzed such as pH value of slurry,concentration,temperature,amount of bleaching agent,bleaching time in the chemical bleaching process of kaolin and light calcium carbonate.

The experiment results show that most iron-bearing impurities can be removed and the kaolin concentrate with high whiteness and lower iron content can be obtained by a method of "Combined processing of chemical bleaching and intensively bleaching with chelator", by co ntrast impurities removal cannot attained by conventional process.