A statistical database (SDB) publishes statistical queries (such as sum, average, count, etc) on subsets of records, and the data in individual records should be remained secret. The key representation auditing scheme is proposed to guarantee the security of online and dynamic SDBs. The core idea is to convert the original database into key representation database (KRDB), also this scheme involves converting each new user query from string representation into key representation query (KRQ), and stores it in the Audit Query table (AQ table). We propose three audit stages to repel the attacks of the snooper to the confidentiality of the individuals. These stages enable the key representation auditor (KRA) to conveniently specify the illegal queries which could lead to disclosing the SDB. Cost estimation for this scheme is performed, and we illustrate the saving in block accesses (CPU time) and storage space that are attainable when a KRDB is used. © 2009 IEEE.