Homomorphic Encryption Ciphertext Conversion for Computation Time Reduction
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Solution Overview
Problem
Fully homomorphic encryption techniques, such as TFHE, face challenges in practicality due to high computation time and large data handling, especially during bootstrapping, which limits the efficiency of operations and the ability to perform complex computations within a reasonable time.
Innovation Solution
An encryption processing apparatus that applies specific polynomials to ciphertexts to reduce operation results to smaller units and convert multiple plaintext symbols to a single symbol, enabling efficient operation between integers without decryption, with error variance controlled in divided regions, facilitating faster and more practical homomorphic operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bootstrapping is performed to reduce error accumulation in fully homomorphic encryption, then decryption reliability is improved, but computation time increases significantly
Solution Approach 1:
The patent segments the homomorphic encryption operations by introducing a conversion step that transforms ciphertexts between different encryption schemes (TFHE to RLWE and vice versa). This segmentation allows error reduction to be performed selectively at conversion points rather than continuously, reducing overall computation time while maintaining decryption reliability.
Solution Approach 2:
The patent introduces RLWE-based ciphertexts as an intermediary form between TFHE ciphertexts. This intermediary allows the system to switch between encryption schemes strategically - using TFHE for efficient bootstrapping operations and RLWE for operations requiring lower computation time, thereby balancing reliability and speed.
2Adaptability or versatility
If TFHE is used for integer-wise homomorphic encryption to perform complex operations, then operational capability is improved, but computation time and data size increase
Solution Approach 1:
The patent dynamically switches between TFHE and RLWE encryption schemes based on the specific operation being performed. TFHE is used when complex integer-wise operations are needed, while RLWE is used for simpler operations or when error reduction is required. This dynamic adaptation optimizes computation time while maintaining operational capability.
Solution Approach 2:
The patent changes the encryption scheme parameter (switching between TFHE and RLWE) depending on the operational requirements. By converting ciphertexts between different encryption frameworks, the system can leverage the strengths of each scheme - TFHE's powerful integer-wise operations and RLWE's efficiency - thereby reducing overall computation time.
3Manufacturing precision
If error variance is controlled in divided regions to improve precision, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the error control process into distinct stages corresponding to different encryption schemes. Error variance is controlled separately in TFHE segments (using bootstrapping) and RLWE segments (using conversion processes). This segmented approach achieves precise error control without requiring a single complex error management system.
Solution Approach 2:
The conversion process between TFHE and RLWE acts as an intermediary mechanism that transfers and transforms error characteristics between encryption schemes. This intermediary step allows the system to leverage the error-control strengths of each scheme separately, achieving high precision without the complexity of a unified error management system.
Data Source
AI summary
An encryption processing apparatus processing a ciphertext is disclosed. The ciphertext is a fully homomorphic ciphertext that has a value with an error as a plaintext associated with an integer and that enables an operation between integers without decryption. The encryption processing apparatus includes a processor which executes the following processes. The processor applies a first polynomial to a first ciphertext to obtain a second ciphertext, the first polynomial being configured to be able to select an operation result in units smaller than a divided region used as one plaintext symbol corresponding to the first ciphertext in a range. The processor further convers two or more of plaintext symbols corresponding to the second ciphertext to the same one plaintext symbol by applying a second polynomial to the second ciphertext, to obtain a third ciphertext corresponding to an operation result of a predetermined operation.