Multi-Secret RLWE Key Switching for Faster Homomorphic Linear Transforms

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Solution Overview

Problem

Conventional homomorphic encryption methods face challenges in processing linear transformations and bootstrapping at high speed due to the time-consuming nature of operations, which hinders efficient processing of homomorphic cryptograms.

Innovation Solution

A device and method for parallel processing of linear key exchange of multiple homomorphic cryptograms using multi secret RLWE, involving packing and transforming cryptograms with a multi secret switching key to reduce bootstrapping time and improve performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional homomorphic encryption methods are used for linear transformation and bootstrapping, then security and encryption functionality are maintained, but processing time is excessive and speed is low

Engineering Contradiction:
Improveprocessing speed of homomorphic encryptionVSAvoidtime for linear transformation and bootstrapping
Core Design Contradiction:
SpeedVSLoss of time

Solution Approach 1:

The patent segments the linear transformation process by separating the linear part from the remaining part of the cryptogram. This allows the linear part to be processed independently and in parallel with other operations, significantly reducing the sequential processing time bottleneck in conventional homomorphic encryption methods

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent merges multiple processing steps into a unified approach where the linear transformation is integrated with the bootstrapping process. By combining these operations and processing them simultaneously where possible, the system reduces the total time required compared to performing them as separate sequential steps

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 3:

The patent performs preliminary processing of the linear part of the cryptogram before the main bootstrapping operation. By pre-processing and preparing the linear components in advance, the system reduces the computational burden during the critical bootstrapping phase, thereby improving overall processing speed

Inventive Principle:
Principle #10Preliminary action

2Productivity

If multiple homomorphic cryptograms are processed sequentially, then processing accuracy is maintained, but productivity is low

Engineering Contradiction:
Improvethroughput of homomorphic cryptogram processingVSAvoidcomplexity of parallel processing system
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent divides multiple homomorphic cryptograms into separate processing streams that can be handled independently. Each cryptogram's linear part is extracted and processed in parallel with others, allowing the system to maintain processing accuracy while significantly increasing throughput through parallel execution

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent creates a universal processing framework that handles multiple types of homomorphic cryptograms using the same parallel processing architecture. The system uses a unified approach for linear part extraction and transformation that works across different cryptogram formats, reducing the need for separate specialized processing paths

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP4645745A1Device and method for linear transformation of homomorphic cryptogram
Publication Date: 2025.11.05 CRYPTO LAB INC
  • EP4645745A1 patent drawingFigure 1
  • EP4645745A1 patent drawingFigure 2
  • EP4645745A1 patent drawingFigure 3

AI summary

A computing device for linearly transforming multiple homomorphic cryptograms is disclosed. The computing device comprises a communication device for receiving an input of multiple homomorphic cryptograms, a memory for storing at least one instruction and the multiple homomorphic cryptograms, and a processor for executing the at least one instruction. The processor executes the at least one instruction to: pack the multiple homomorphic cryptograms by using multi-secret RLWE that share a linear part of the cryptograms; and perform key exchange of the packed multi-secret RLWE cryptograms by using a multi-secret switching key obtained in the format of multi secret RLWE.