Re-encryption Strategy for Encrypted Database Joins
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Solution Overview
Problem
Existing encrypted databases face inefficiencies in dynamically adjusting encryption during join operations, leading to an infinite number of re-encryptions and sub-optimal performance, as naive approaches fail to efficiently select columns for re-encryption under varying query schedules.
Innovation Solution
The method involves determining the ranks of encryption keys associated with columns to be joined, selecting the column with the lower rank for re-encryption, updating the ranks, and deleting keys when necessary, ensuring that re-encryption is performed optimally with a bound of at most O(n3/2) re-encryptions for n columns, and enhancing this by considering cluster keys and non-uniform costs to minimize re-encryption costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If naive approaches to column selection are used for re-encryption, then the database can perform join operations on encrypted data, but the number of re-encryptions becomes infinite and performance deteriorates
Solution Approach 1:
The patent introduces a ranking parameter for encryption keys and changes the re-encryption strategy based on rank comparisons. Instead of arbitrary column selection, the system selects columns for re-encryption based on their key ranks, ensuring that each re-encryption operation reduces the total rank sum by a guaranteed amount, thereby bounding the total number of re-encryptions.
Solution Approach 2:
The system maintains and updates rank values for each encryption key, using this feedback information to make informed decisions about which columns to re-encrypt. The rank metric provides continuous feedback on the state of encryption keys, guiding the selection process to avoid infinite re-encryptions.
2Reliability
If the database dynamically adjusts encryption by re-encrypting columns during join operations, then security is maintained against cryptanalysis, but the complexity of key management increases
Solution Approach 1:
The patent introduces an intermediary ranking system that mediates between the encryption keys and the join operations. Rather than directly managing complex key relationships, the system uses ranks as an intermediary metric to guide re-encryption decisions, simplifying key management while maintaining security.
Solution Approach 2:
The system transforms the key management problem into a parameter-based problem by assigning and manipulating rank values. This parameter change approach converts complex key relationship management into simpler numerical comparisons and updates, reducing management complexity while preserving security properties.
3Adaptability or versatility
If multiple columns are re-encrypted to enable join operations, then the join functionality is achieved, but the cost of re-encryption operations increases
Solution Approach 1:
The patent introduces a cost parameter for each column re-encryption operation and uses rank differences to bound the total cost. By selecting columns for re-encryption based on rank comparisons rather than arbitrary selection, the system guarantees that each operation contributes to reducing the total cost, achieving join functionality with bounded re-encryption expenses.
Data Source
AI summary
Methods, systems, and computer-readable storage media for selecting columns for re-encryption in join operations. In some implementations, actions include determining a first column and a second column to be joined, receiving a first key corresponding to the first column and a second key corresponding to the second column, receiving a first rank associated with the first key and a second rank associated with the second key, selecting the second column for re-encryption based on the first rank and the second rank, and providing the first column, the second column, and the first key for performing a join operation, the second column being re-encrypted based on the first key.