Importance

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Abstract

A distributed computer system has an information server and a plurality of client computers coupled by one or more communication paths to the information server. The information server includes a database management system (DBMS) with an interface procedure for receiving and responding to SQL statements from client computers. At least one client computer has a database access procedure for sending SQL statements to the DBMS in the information server. The database access procedure includes embedded encrypted SQL statements, representing a predefined subset of a predefined full set of SQL statements recognized as legal SQL statements by the DBMS. For instance, the predefined subset of SQL statement might include only SQL statements for reading data in the DBMS, but not include SQL statements for modifying and adding data to the DBMS. Each of the SQL statements sent by the database access procedure to the DBMS includes a corresponding one of the encrypted SQL statements. The DBMS in the information server includes an interface procedure for processing all SQL statements received from client computers, including a decoding procedure for decoding the encrypted SQL statement included in the SQL statements sent by the database access procedure in the one client computer. The received SQL statement is executed by the DBMS only if the decoded SQL statement is a legal SQL statement. In addition, the interface procedure rejects received SQL statements that do not include an encrypted SQL statement.

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First Claim