Protection of data of database clients from persistent adversaries

An apparatus, comprising:

• at least one processor;
• and
• a computer readable storage medium having computer readable program code embodied therewith and executable by the at least one processor;
• wherein the computer readable program code is configured to receive, at a database proxy acting as an intermediary between a plurality of database clients and a service provider providing data management services for the plurality of database clients, a set of queries, of at least one of the plurality of database clients, for data stored at the service provider in an encrypted form, wherein the database proxy maintains a security budget defining a maximum threshold amount of data leakage for the plurality of database clients;
• wherein the computer readable program code is configured to batch, at the database proxy, the set of queries into query batches;
• wherein the computer readable program code is configured to transform, at the database proxy and for each query batch, each query within the query batch, wherein the transforming comprises changing the query to reduce data leakage;
• wherein the computer readable program code is configured to perform, at the database proxy and responsive to transforming each query within the query batch, a transformation on each of the query batches to reduce data leakage;
• wherein the computer readable program code is configured to execute, at the database proxy and utilizing an order-preserving encryption algorithm, the query batches;
• and
• wherein the computer readable program code is configured to calculate, at the database proxy, a remaining security budget based upon data leakage resulting from the executing of the query batches.

A computer program product, comprising:

• a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code executable by a processor;
• wherein the computer readable program code is configured to receive, at a database proxy acting as an intermediary between a plurality of database clients and a service provider providing data management services for the plurality of database clients, a set of queries, of at least one of the plurality of database clients, for data stored at the service provider in an encrypted form, wherein the database proxy maintains a security budget defining a maximum threshold amount of data leakage for the plurality of database clients;
• wherein the computer readable program code is configured to batch, at the database proxy, the set of queries into query batches;
• wherein the computer readable program code is configured to transform, at the database proxy and for each query batch, each query within the query batch, wherein the transforming comprises changing the query to reduce data leakage;
• wherein the computer readable program code is configured to perform, at the database proxy and responsive to transforming each query within the query batch, a transformation on each of the query batches to reduce data leakage;
• wherein the computer readable program code is configured to execute, at the database proxy and utilizing an order-preserving encryption algorithm, the query batches;
• and
• wherein the computer readable program code is configured to calculate, at the database proxy, a remaining security budget based upon data leakage resulting from the executing of the query batches.