Zero Knowledge Proof for Shop Purchaser Identity Verification
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Solution Overview
Problem
Existing online sales systems using group signature schemes face challenges in balancing user anonymity with the ability to handle inquiries and services related to past purchases, as unlinkability hinders direct communication between users and service providers, making it difficult to track user behavior and offer personalized services.
Innovation Solution
Implementing a system with a shop apparatus and purchaser apparatus that utilize a group signature scheme with tracing functionality, allowing for the storage and verification of anonymous order information, including an order ID and purchaser identity verifying information, enabling the elimination of unlinkability when necessary through zero knowledge proofs, thereby facilitating inquiries and services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unlinkability is maintained in group signature scheme, then protection of personal information and privacy is improved, but ability to handle inquiries and services related to past purchases deteriorates
Solution Approach 1:
The system dynamically adjusts the level of anonymity based on the operation phase. During order placement, full unlinkability is maintained for privacy protection. During inquiry processing, the system transitions to a state where linkability is enabled through zero-knowledge proofs, allowing service providers to verify user identity for past orders without compromising future anonymity. This dynamic switching resolves the contradiction between privacy protection and service accessibility.
Solution Approach 2:
The system changes the cryptographic parameters from completely anonymous group signatures to zero-knowledge proof verification. By transforming the verification mechanism, the system maintains the protective function of anonymity while enabling the service function of identifiable verification. This parameter change allows the same user to be verified across multiple interactions without revealing personal information, thus resolving the contradiction.
2Reliability
If unlinkability is given to purchased goods and services, then protection of personal information is improved, but number of times user uses service provider becomes unknown
Solution Approach 1:
Zero-knowledge proofs act as an intermediary mechanism that enables the service provider to verify usage frequency and user identity without directly accessing personal information. The proof system mediates between the need for anonymity and the need for usage tracking, allowing the provider to obtain usage statistics while the user's personal identity remains protected. This resolves the contradiction by losing only minimal aggregated information while maintaining strong privacy protection.
Solution Approach 2:
The system implements a feedback mechanism where usage information is verified and stored through zero-knowledge proofs. Each purchase interaction generates verifiable proof that feeds back into the system, allowing the service provider to accumulate usage frequency data and provide personalized services. This feedback loop maintains privacy while enabling the collection of necessary usage information for service improvement.
3Reliability
If anonymity is maintained, then privacy protection is improved, but direct communication between user and service provider deteriorates
Solution Approach 1:
The communication system is segmented into two distinct modes: anonymous order placement and verified inquiry processing. During order placement, complete anonymity is maintained. During inquiries, the system segments the verification process using zero-knowledge proofs, allowing direct communication only when necessary and with proper authentication. This segmentation resolves the contradiction by enabling direct communication only when needed while maintaining anonymity during routine transactions.
Solution Approach 2:
The system performs preliminary authentication through zero-knowledge proofs before enabling direct communication for inquiries. This preliminary action verifies the user's identity and authority to make inquiries about past orders without revealing personal information during the actual communication. By performing this authentication step in advance, the system enables direct communication while maintaining privacy protection throughout the process.
Data Source
AI summary
A purchaser apparatus stores “anonymous order information including an order ID and purchaser identity verifying information” and “purchaser identity proving secret information”. A shop apparatus stores “anonymous order information including an order ID and purchaser identity verifying information”. If necessary, a purchaser sends a request including an order ID and zero knowledge proving information that a purchaser knows the purchaser identity proving secret information, from a purchaser apparatus to a shop apparatus. A shop apparatus verifies the zero knowledge proving information, based on purchaser identity verifying information retrieved from an order ID included in the request. Therefore, the unlinkability for past use is eliminated if necessary, and inconvenience caused by the unlinkability is eliminated.