Abstract: This paper elaborated the goal of privacy preserving data mining,that is to satisfy the demand of users for privacy protection as we acquire the mining results of effective data mining.For privacy protection to individual users and group users,this paper discussed different methods,and summed up two main algorithms in data mining of privacy preservation.Since efficient mining associations with secrecy konstraints(EMASK) needs full database scan and many comparison operations,the author came up with efficient mining associations with secrecy konstraints which is based on Bitmap computation(BEMASK).It transforms relational data form into relational model for machine,data processing is converted into granular computing method and calculation of frequent item-sets is turned into computing the intersection set of basic particles.Especially the vertical representation of Bitmap,under the condition of ensuring that accuracy is not reduced,on one hand reduces the number of I/O operations,on the other hand,greatly improves the efficiency.

Key words: Data mining,Privacy preserving,Frequent pattern,Knowledge granularity