Trusted Machine for Encrypted Database Query Processing

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Solution Overview

Problem

Conventional encrypted database management systems (EDBMS) face security issues as adversaries can reconstruct the plaintext content of data by correlating query parameters with query results, leading to full disclosure, compromising data confidentiality.

Innovation Solution

Implementing a semantically secure EDBMS with a trusted machine that decrypts and processes encrypted queries using semantically secure query operators, enforcing an upper bound on query result records, and encrypting results to prevent information leakage, thereby masking correlations between query parameters and results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If encrypted database management systems store data remotely and allow query access, then data accessibility and network retrieval capability are improved, but data confidentiality and security deteriorate because adversaries can correlate query parameters with query results to reconstruct plaintext content

Engineering Contradiction:

Improvedata accessibilityVSAvoiddata security

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary trusted machine between the untrusted database server and the client. This trusted machine acts as a mediator that receives encrypted queries, executes them on the untrusted server, and returns results to the client. The intermediary prevents direct correlation between query parameters and results by the adversary, thus protecting data confidentiality while maintaining accessibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system segments the database management functionality into two parts: an untrusted server for storing and processing encrypted data, and a trusted machine for managing encryption keys and coordinating secure query execution. This segmentation allows the untrusted server to handle data operations while the trusted machine ensures security, resolving the contradiction between accessibility and security.

Inventive Principle:

Principle #1Segmentation

2Productivity

If conventional EDBMS processes queries directly on the server, then processing efficiency is improved, but semantic security deteriorates because query result sizes reveal information about the plaintext content

Engineering Contradiction:

Improvequery processing efficiencyVSAvoidinformation leakage

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The trusted machine serves as an intermediary that receives encrypted queries from clients, forwards them to the untrusted server, and processes the results before returning them to clients. This intermediary layer prevents the adversary from directly observing the correlation between query parameters and result sizes, thereby preventing information leakage while maintaining efficient query processing through the untrusted server.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the parameter of query result presentation by encrypting results and controlling the number of records returned. The trusted machine modifies the query execution parameters to ensure that result sizes do not reveal information about the underlying plaintext data, thus preventing information leakage while maintaining processing efficiency.

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If the system returns all query results without restriction, then completeness of data retrieval is improved, but security deteriorates due to potential disclosure of sensitive information through result cardinality

Engineering Contradiction:

Improvedata completenessVSAvoidinformation disclosure

Core Design Contradiction:

Loss of informationVSObject-affected harmful factors

Solution Approach 1:

The trusted machine implements a security policy that limits the number of records returned in query results to a predetermined maximum. This partial action approach ensures that even if an adversary gains access to query results, they cannot obtain more than a limited amount of information, thus preventing complete disclosure of sensitive data while still providing useful query functionality.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system implements feedback control by monitoring the number of records in query results and adjusting the output accordingly. The trusted machine enforces an upper bound on result cardinality, providing feedback that prevents information disclosure through result size while maintaining data completeness within security constraints.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9953184B2Customized trusted computer for secure data processing and storage

Publication Date: 2018.04.24 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

The techniques discussed herein facilitate the transmission, storage, and manipulation of data in an encrypted database management system (EDBMS). An untrusted machine is connected to a data store having encrypted records, a client machine that sends encrypted queries, and a trusted machine that receives and decrypts the encrypted records and encrypted queries. The trusted machine processes the query using semantically secure query operators to produce a query result. The trusted machine ensures the size of the query result conforms to an upper bound on the number or records in the query result and returns the query result.