Fully Homomorphic Encryption Device Bootstrapping Optimization
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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 on encrypted data.
Innovation Solution
An encryption processing device that employs specific polynomials and bootstrapping methods to decompose functions into odd and even components, allowing for faster homomorphic operations on fully homomorphic ciphertexts by reducing error accumulation and optimizing computation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bootstrapping is performed to reduce error component in fully homomorphic encryption, then decryption reliability is improved, but computation time increases significantly
Solution Approach 1:
The patent segments the bootstrapping process by introducing a first bootstrapping unit that performs initial error reduction and a second bootstrapping unit that performs additional error reduction. This segmentation allows the computation to be divided into manageable phases, each handling specific error reduction tasks, thereby improving overall efficiency while maintaining decryption reliability.
Solution Approach 2:
The first bootstrapping unit performs preliminary error reduction before the second bootstrapping unit operates. By performing error reduction in advance through the first bootstrapping unit, the system prepares the ciphertext in a state that requires less computational effort for the second bootstrapping unit, thus reducing total computation time while ensuring decryption reliability.
2Reliability
If bootstrapping handles large amount of data to reduce error, then decryption reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the bootstrapping functionality into separate units (first bootstrapping unit and second bootstrapping unit), each handling specific portions of the error reduction process. This segmentation reduces the complexity of any single unit while maintaining the overall reliability through coordinated operation of multiple simpler units.
Solution Approach 2:
The patent introduces intermediate structures including a first polynomial and second polynomial that mediate between the input ciphertext and the final output. These intermediaries break down the complex error reduction process into manageable mathematical operations, reducing system complexity while preserving decryption reliability.
3Reliability
If conventional bootstrapping methods are used, then error reduction is achieved, but productivity decreases due to large computation requirements
Solution Approach 1:
The first bootstrapping unit performs preliminary error reduction operations that prepare the ciphertext for more efficient processing by the second bootstrapping unit. This preliminary action reduces the computational burden of subsequent operations, thereby improving productivity while maintaining error reduction effectiveness.
Solution Approach 2:
The patent changes parameters by introducing different polynomials (first polynomial and second polynomial) with specific properties that optimize the bootstrapping process. By carefully selecting and changing these mathematical parameters, the system achieves effective error reduction with reduced computational complexity, improving productivity.
Data Source
AI summary
A fully homomorphic encryption processing device processing a ciphertext is disclosed, the ciphertext has an integer as a plaintext. The encryption processing device includes a processor that executes a process including: obtaining a ciphertext by using a first polynomial and a second polynomial respectively including a second function and a third function, the second function and the third function being generated by decomposing a first function as a calculation object. The processor also applies the first polynomial to a first ciphertext to obtain a second ciphertext. The processor further applies the second polynomial to a ciphertext obtained by calculation based on applying a predetermined polynomial to the first ciphertext to obtain a third ciphertext. The processor performs a homomorphic operation using the second ciphertext and the third ciphertext to obtain a fourth ciphertext corresponding to a result of calculation of the first function which uses the first ciphertext as input.