E-cash Payment Coin Attribute Segmentation for Partial Spending
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Solution Overview
Problem
Existing e-cash systems face challenges such as significant computational and storage overhead, lack of change or refunds, and impractical data management due to their design, particularly in divisible e-cash schemes, which are inefficient and costly for large-scale implementations.
Innovation Solution
A method for managing e-cash transactions using a payment coin based on a combination of attributes, where each attribute represents a portion of the total value, allowing partial spending and refunding without requiring trust between the bank and merchant, using blind signature schemes and double-refund checks to ensure security and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a divisible e-cash scheme is implemented to allow partial spending of coins, then transaction flexibility is improved, but storage overhead increases to several megabytes per coin
Solution Approach 1:
The payment coin is segmented into multiple attributes, where each attribute represents a different portion of the total value. This allows the coin to be divided into spendable portions without storing the entire coin data structure repeatedly, reducing storage overhead while maintaining transaction flexibility.
Solution Approach 2:
The patent transforms the storage problem from storing large binary representations of divisible coin values to storing structured attribute data with mathematical relationships. By organizing coin value information in a dimensional attribute space rather than linear storage, the system achieves efficient partial spending capability with reduced storage requirements.
2Adaptability or versatility
If a divisible e-cash scheme is implemented to allow partial spending of coins, then transaction flexibility is improved, but computational costs become prohibitive
Solution Approach 1:
The system performs preliminary setup by establishing mathematical relationships between coin attributes during coin creation. The commitment structure and attribute relationships are pre-configured using blind signatures, so that during actual spending operations, only lightweight verification and subset selection are needed, dramatically reducing computational costs at transaction time.
Solution Approach 2:
The patent changes the computational parameters by using cryptographic commitments and blind signatures instead of traditional divisible e-cash mathematical structures. This transformation reduces the complexity of partial spending operations from exponential to polynomial time, making the system computationally feasible while maintaining divisibility.
3Reliability
If a refundable e-cash scheme is implemented to allow change, then transaction completeness is improved, but trust requirements between merchant and bank increase
Solution Approach 1:
The system enables self-service refunds where the buyer can independently redeem unspent coin portions from the bank without merchant involvement. The cryptographic structure allows the buyer to prove ownership and request refunds autonomously, eliminating the need for merchant-bank trust relationships while ensuring complete transaction handling.
Solution Approach 2:
The patent introduces cryptographic commitments and blind signatures as intermediaries between the buyer, merchant, and bank. These cryptographic mechanisms mediate the refund process, allowing the bank to verify refund requests without trusting the merchant, and enabling buyers to receive refunds without direct bank-merchant interaction, thus reducing trust requirements.
Data Source
AI summary
A method for managing an anonymous e-cash transaction includes receiving a request to withdraw a payment coin, generating a combination of random attributes for the payment coin, creating the payment coin based on the combination of attributes, and issuing the payment coin in exchange for a first asset. Each attribute of the combination of attributes may represent a different portion of a total value of the payment coin. A partially spent value of the payment coin may be based on a revealed subset of the combination of attributes. The method further includescreating a refund coin based on the combination of attributes and spending the refund coin to issue a refund having a value corresponding to an unspent portion of the payment coin. Each attribute of the combination of attributes of the refund coin may represent a different portion of a total value of the refund coin.