Transcryptor-Based Homomorphic Ciphertext Processing for Low-Communication MPC
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Solution Overview
Problem
Conventional threshold fully homomorphic encryption methods require excessive communication and inefficient noise addition, leading to high communication volume and inefficiency in multi-party computations.
Innovation Solution
A method involving a transcryptor and a system of electronic apparatuses using a non-threshold fully homomorphic encryption scheme, where a second public key is generated to enable homomorphic computations, followed by partial decryption and combination of results among qualified groups, with end-to-end encryption for secure communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threshold fully homomorphic encryption is used to perform multi-party computations, then security is improved through key splitting and partial decryption, but communication volume increases excessively due to noise addition requirements
Solution Approach 1:
The patent introduces a transcryptor as an intermediary component that receives ciphertext from multiple parties, performs the homomorphic computation, and distributes the result back to parties. This mediator approach consolidates the computation process, reducing the need for extensive inter-party communication and noise management that would otherwise be required in direct multi-party threshold FHE protocols.
Solution Approach 2:
The patent segments the threshold FHE process into distinct phases: key generation phase where secret keys are split among parties, encryption phase where individual parties encrypt their data, computation phase performed by the transcryptor, and decryption phase where partial decryptions are combined. This segmentation allows each phase to be optimized independently, reducing overall communication overhead.
2Reliability
If conventional threshold fully homomorphic encryption is used to ensure secure multi-party computation, then security is improved through partial decryption mechanisms, but computational efficiency deteriorates due to exponential noise addition requirements
Solution Approach 1:
The transcryptor serves as a dedicated intermediary that handles the computationally intensive homomorphic computation and noise management tasks. By centralizing these operations in a specialized component rather than distributing them across all participating parties, the system achieves better computational efficiency while maintaining the security benefits of threshold decryption.
Solution Approach 2:
The patent replaces the traditional mechanical approach of having each party perform noise addition and management operations with an automated cryptographic system implemented in the transcryptor. This substitution uses advanced homomorphic encryption algorithms to automatically manage noise growth and reduction, significantly improving computational efficiency compared to manual or distributed noise management approaches.
Data Source
AI summary
Provided is a control method of a system including a plurality of electronic apparatuses, a transcryptor, and a server. The method includes: obtaining, by the apparatuses included in the system, a first public key for the apparatuses included in the system by using a threshold public key encryption scheme, and obtaining, by each of the plurality of electronic apparatuses, a secret key share corresponding to each apparatus; generating, by the transcryptor, a second public key and a private key based on a non-threshold fully homomorphic encryption scheme, and providing the second public key to the server and the plurality of electronic apparatuses; generating a ciphertext, by each of the plurality of electronic apparatuses, by encrypting plaintext data using the second public key, and then transmitting the generated ciphertext to the server; obtaining, by the server, a homomorphic computation ciphertext by performing homomorphic computation on the received ciphertext using a circuit for combining threshold public key encryption; transmitting, by the server, the homomorphic computation ciphertext to the transcryptor; decrypting, by the transcryptor, the homomorphic computation ciphertext using the private key, and broadcasting the decrypted homomorphic computation ciphertext to the plurality of electronic apparatuses; and obtaining a final decryption result, by a qualified group of electronic apparatuses among the plurality of electronic apparatuses, by performing partial decryption on the homomorphic computation ciphertext using the secret key shares and by combining the partial decryption results.