Re-Encryption Key Generation for Generic FHE-to-HPRE Conversion
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Solution Overview
Problem
Existing methods for secure data transfer using Fully Homomorphic Encryption (FHE) and Proxy Re-Encryption (PRE) schemes are vulnerable to collusion attacks and do not support generic conversion of multiple types of FHE schemes, compromising security and flexibility in data transmission.
Innovation Solution
A method and system for re-encrypting encrypted data using a re-encryption key generated by splitting and consolidating parts of public-private key pairs, enabling secure data transfer without sending the re-encryption key, and supporting conversion of any FHE scheme to a Homomorphic Proxy Re-Encryption (HPRE) scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If re-encrypted ciphertext is transmitted along with the re-encryption key, then the second user can decrypt the ciphertext, but the system becomes vulnerable to collusion attacks
Solution Approach 1:
The patent extracts the re-encryption key from the transmission process entirely. The system generates re-encryption keys locally at each user's device without transmitting them through the proxy server or network, eliminating the security vulnerability while maintaining decryptability through local key management
Solution Approach 2:
The proxy server acts as an intermediary that performs re-encryption operations without ever possessing or transmitting the re-encryption keys. The server mediates the conversion between encryption schemes while the keys remain securely localized at user devices, preventing collusion attacks
2Reliability
If separate handling is used for different FHE schemes, then each scheme can be processed correctly, but the system complexity increases and generic conversion is not supported
Solution Approach 1:
The patent implements a universal proxy re-encryption mechanism that can handle multiple FHE schemes (BFV, BGV, CKKS, TFHE) through a single unified framework. The system uses generic algorithms that automatically adapt to the specific scheme being used, eliminating the need for separate handling of each scheme while maintaining correctness
Solution Approach 2:
The system changes parameters dynamically based on the input FHE scheme type. The generic conversion framework adjusts its internal parameters and operations according to the specific scheme being converted, allowing single code to handle multiple schemes correctly without increasing overall system complexity
Data Source
AI summary
This disclosure relates generally to a method and system for re-encryption of an encrypted data. State-of-the-art methods provide the re-encryption scheme for a specific Fully Homomorphic Encryption (FHE) encrypted data. However, a generic scheme that converts any given FHE scheme to an HPRE scheme is not yet achieved. The disclosed method provides re-encryption of the encrypted data transferred between a first user and a second user by a re-encryption key. The re-encryption key is obtained by splitting a private key of the first user into a primary private key and a secondary private key. The primary private key generates a public re-key component using probabilistic encryption algorithm; and the secondary private key generates a private re-key component using probabilistic switch key generation algorithm. Both the private re-key and the public re-key are consolidated further to generate the re-encryption key.