Homomorphic Encryption Key Switching for Lower-Memory Blind Rotation
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Solution Overview
Problem
Existing homomorphic encryption techniques face challenges with large public key sizes and high memory requirements, particularly in blind rotation operations, which impact computational efficiency and speed.
Innovation Solution
A method and apparatus that utilize a key-switching operation to generate a second ciphertext with reduced dimensions and a scaled-up secret key, combined with a blind rotation operation using an operation key, to reduce computational demands and memory usage while maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If blind rotation operation is used to perform arbitrary function operations on ciphertext messages, then operation accuracy is improved, but public key size becomes significantly large
Solution Approach 1:
The patent segments the blind rotation operation into two distinct phases: a key switching operation that reduces ciphertext dimensions, and a subsequent blind rotation operation on the reduced-dimensional ciphertext. This segmentation allows the system to achieve accurate blind rotation results while working with smaller public key sizes, as the key switching phase prepares the ciphertext in a form that requires smaller keys for the rotation phase.
Solution Approach 2:
The key switching operation is performed as a preliminary action before the blind rotation operation. By first reducing the ciphertext dimensions through key switching, the system prepares the data in an optimized state that enables subsequent blind rotation to be performed with smaller public keys, thereby resolving the contradiction between accuracy and key size.
2Adaptability or versatility
If blind rotation operation is performed, then arbitrary function operations can be executed, but memory requirements increase significantly
Solution Approach 1:
The patent divides the memory-intensive blind rotation operation into two stages: key switching (which reduces dimensional complexity) and blind rotation on reduced data. This segmentation reduces the peak memory requirements while preserving the ability to perform arbitrary function operations on encrypted data.
3Productivity
If public key size is reduced to improve efficiency, then computational speed increases, but the amount of computation greatly increases
Solution Approach 1:
The key switching operation serves as a preliminary computational step that reduces ciphertext dimensions before the main blind rotation operation. While this adds some initial computation, it enables subsequent operations to proceed faster with smaller keys, achieving an overall improvement in computational efficiency and speed.
Solution Approach 2:
The patent changes the dimensional parameters of the ciphertext through key switching, transforming high-dimensional ciphertext into lower-dimensional form. This parameter change allows the system to use smaller public keys and perform operations more efficiently, balancing the trade-off between initial computation and overall processing speed.
Data Source
AI summary
An apparatus and method with homomorphic encryption are provided. A method for performing a homomorphic encryption operation may include generating a second ciphertext, having a second total number of dimensions, by performing a key switching operation using a key-switching key to generate the second ciphertext, encrypted by a second secret key, based on a homomorphic encrypted first ciphertext on a first modulus encrypted by a first secret key, where the first ciphertext has a first total number of dimensions, and generating a ciphertext on a second modulus by performing a blind rotation operation based on the second ciphertext and an operation key.