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Voucher-integrated C2B and C2C Trading Model

Makoto Iguchi, Masayuki Terada, Yoshitaka Nakamura, and Ko Fujimura
NTT Information Sharing Platform Laboratories, NTT Corporation
1-1 Hikarinooka Yokosuka, Kanagawa, 239-0847, Japan
TEL: +81-468-59-2663 FAX: +81-468-59-8329
{iguchi, te, yoshitaka, fujimura}@isl.ntt.co.jp


The demand for consumer-initiated trading models, namely Consumer-to-Business (C2B) and Consumer-to-Consumer (C2C) models, is expected to increase in the next few years. We must be able to support the development of e-commerce systems that cover these e-commerce models, yet existing EC construction tools merely focus on Business-to-Business (B2B) and Business-to-Consumer (B2C) models. In this paper we propose a trading model for supporting C2B and C2C e-commerce through the use of digital media called vouchers. The proposed model utilizes vouchers and the voucher trading system (VTS) to form a trading framework for C2B and C2C e-commerce. The trading framework uniformly realizes the delivery/payment component of each transaction. Once the framework is built, developers can construct C2B and C2C e-commerce systems simple by adding to only the matching components.


E-commerce, C2C (Consumer-to-Consumer) trading, C2B (Consumer-to-Business) trading, Voucher, Voucher Trading System (VTS)


Many analysts state that C2B and C2C e-commerce will thrive in the near future [1]. It is a challenging task, however, to construct these e-commerce systems because of their diverse nature. The existing EC construction tools, which usually focus on B2B and B2C e-commerce schemes, were designed for constructing specific e-commerce systems, making them unsuitable for developing consumer-initiated e-commerce systems. In this paper, we propose a trading model that supports C2B and C2C e-commerce through the use of digital media called gvouchersh and the trading system gVTSh [2]. We show how the introduction of vouchers simplifies the procedures of C2B and C2C e-commerce, and show that vouchers, together with VTS, can be utilized to form a trading framework that uniformly realizes the delivery/payment phase. We demonstrate that a wide range of matching phase implementations, in which the characteristics of specific e-commerce systems such as market coordination are implemented, can be integrated into this framework. Our prototype implementation of the model is also introduced.

2. Voucher-integrated C2B and C2C trading model

There exist a great number of C2B and C2C business schemes, and each has diverse characteristics. For instance, they differ in their matching logics (auctioning, reverse-auctioning, etcc), in their target objects (books, mp3 files, admission tickets, etcc), in their payment/delivery method, and in their agreement/contract handling (compensation statement, terms of responsibility statement, etcc). It is these diversities that make the development of C2B and C2C trading system arduous.

We can ease these problem by introducting gvouchersh and their trading system gVTSh to C2B and C2C e-commerce procedures. A voucher is a digital representation of the right to claim goods or services, and is composed of promise and issuer information. The conversion of voucher into the merchandise described in the promise is guaranteed by the issuer of the vouchers. The definition of the promise in the voucher is expressed using XML to allow flexible description of merchandise and services. The VTS provides a means to generate vouchers and to circulate them among the users while preventing forgery, alteration, or reproduction. VTS itself only provides one-way transfer of vouchers, but it can be integrated with either a fair exchange protocol of electronic data [3] or with an escrow barter services to achieve the fair exchange of vouchers.

The introduction of vouchers enables systems to represent a wide range of merchandise and monetary values in forms of vouchers. Once represented as vouchers, they can be transferred by the same VTS, and both the payment for the merchandise and the delivery of the merchandise can be realized by transferring the corresponding vouchers. This removes the difficulty of the diversity of target objects and payment/delivery method. The introduction of VTS, together with fair exchange integration, enables systems to resolve the atomicity of delivery and payment transactions. This simplifies the agreement because the agreement only has to define which vouchers are to be exchanged between which participants. The exchange of vouchers itself is guaranteed by the exchange protocol, so a complex contract defining terms of compensation and responsibility in the event of delivery or payment transaction failure is no longer required.

Figure 1
Figure 1: Voucher-integrated C2B and C2C trading model

Figure 1 shows the proposed trading model with voucher and VTS integration. The model clearly separates the matching phase from the delivery/payment phase. In the matching phase, the participants are matched following the appropriate market coordination for the schemes. An agreement that defines which vouchers are to be exchange between which participants is formed at the end of the matching phase. At the delivery/payment phase, a fair exchange of the vouchers is conducted as defined by the agreement.

In the model, the delivery/payment phase acts as a unified framework for C2B and C2C trading. Once this framework is implemented, developers can built C2B and C2C e-commerce systems by adding the desired matching phase implementations (e.g. matching system with second price sealed bid auctioning or simple gshopping cart styleh system) to the framework. There is only one obligation placed on the matching system, that is, at the end of the matching phase, an agreement should be generated that lists the vouchers to be exchanged and participants exchanging them.

3. Examples

To demonstrate the practicability of our voucher-integrated trading model, we provide an example of an auction system implemented using our model. We will assume that voucher A, which represents the item to be sold, issued by the manufacturer, while voucher B, which consists 50 pieces of monetary value (each piece equals one dollar), issued by a bank, exist prior to commencing the auction.

In the matching phase, the matching phase implementation determines how the auction is executed. The auction can be either open bid auction (English auction or Dutch auction) or sealed bid auction (first price auction or second price auction), as long as the result of the auction is appropriately summarized in an agreement. In the auction scenario, a winner is determined from bidders at the end of the matching phase, and at this point vouchers to be traded are also determined. Let us assume that the winner bid the price of 50 dollars. The agreement would then state that voucher A of the seller is to be exchanged for 50 pieces of voucher B held by th bidder.

In the delivery/payment phase, voucher A and 50 pieces of voucher B are exchanged between the seller and the bidder as defined in the agreement. The exchange is conducted using VTS with the fair exchange option, thereby ensuring the security and fairness of the exchange. Once the vouchers are successfully traded, the seller converts voucher B to its monetary value, and the bidder converts voucher A into the item. These conversions are guaranteed by the vouchers, or more precisely by the issuers of the vouchers.

4. Prototype Implementation

We have implemented a prototype of our trading model. Currently, our prototype supports a matching scheme that provides goffering for exchangehand gaccepting an offerh. In this scheme, a user first registers an offer in which his/her intention of goffering voucher(s) in exchange for other voucher(s)h is described. Then, another user, after confirming the offer and finding it satisfactory, accepts the offer. Upon the acceptance, the corresponding agreement is generated by the system.

Figure 2
Figure 2: Agreement Established within the Protocol System

Figure 2 shows a screenshot of the user confirming and accepting the offer. After the offer is confirmed and accepted (left-hand side of Figure 2), the corresponding agreement is created (right-hand size of Figure 2). The delivery/payment phase is executed by the system according to this agreement.

5. Conclusion

We proposed a trading model that integrates vouchers and VTS for supporting C2B and C2C e-commerce. By realizing the fair exchange of vouchers, the model provides a unified trading framework for C2B and C2B e-commerce system. Once the framework is built, developers can construct C2B and C2C e-commerce systems simple by adding just their matching modules to this framework. The prototype implementation of our trade model is also introduces.

The more information on our work can be found on our website [4].


  1. Reuters News Releases, gTowerGroup Research Finds Rapid Growth in Number of Internet Person-to-Person Payment Accounts a Deceptive Indicator,h Jan. 31, 2001,
  2. K. Fujimura, gRequirements for Genetic Voucher Trading,h IETF Internet Draft,
    http://www.ietf.org/internet-drafts/draft-ietf-trade-drt-requirements-03.txt, 2002.
  3. J. Zhou, gNon-repudiation in Electronic Commerce,h Artech House, Inc., 2001.
  4. FlexTicket Official Home Page,