Abstract: The Apriori algorithm is a milestone in the development of data mining. A number of other algorithms, which generate association rules by producing frectuent itemsets,are derived from it. This paper proposed a data preprocessing algorithm based on item closure, which is an absolutely new method for privacy-preserving data mining. According to the characteristics and the processes of Apriori-like algorithms, this method transforms different items in various ways.So the data mining applicant can only obtain the information of its own products correctly, but cannot obtain useful information regarding its potential competitors' products. Hence, through the application of this method, the cooperated data mining between the data provider and data miner will benefit both sides, and obtains a win-win result.

Key words: Apriori algorithm, Privacy-prescrving, Item closure, Data mining