Complementary currencies in the context of P2P (peer-to-peer) networks can be powerful tools for promoting exchanges and building sustainable relationships among selfish peers on the Internet. i-WAT [K. Saito, Peer-to-peer money: Free currency over the Internet, in: Proceedings of the Second International Conference on Human.Society@Internet, HSI 2003, in: Lecture Notes in Computer Science, vol. 2713, Springer-Verlag, 2003] (Internet WAT) has been proposed as such a currency based on the WAT System [watsystems.net, WATSystems home page, hypertext document. Available electronically at http://www.watsystems.net/], a polycentric, real-life complementary currency using WAT tickets as its media of exchange
participants spontaneously issue and circulate the tickets, whose values are backed up by chains of trust, as needed. This article investigates the claim made in the past [K. Saito, E. Morino, J. Murai, Incentive- compatibility in a distributed autonomous currency system, in: Proceedings of the Fourth International Workshop on Agents and Peer-to-Peer Computing, AP2PC 2005, 2005] that the design of i-WAT is incentive-compatible as to counteraction against moral hazards. Such hazards are impeded in i-WAT because participants will have to take natural evasive actions to avoid apparent risks posed by misbehaviors of others. This effect is measured for regular tickets, whose values remain constant over time, as well as for reduction [K. Saito, E. Morino, J. Murai, Reduction over time to facilitate peer-to-peer barter relationships, IEICE Transactions on Information and Systems E89-D (1)] and multiplication [K. Saito, E. Morino, J. Murai, Multiplication over time to facilitate peer-to-peer barter relationships, in: Proceedings of the 2nd International Workshop on P2P Data Management, Security and Trust, PDMST '05, 2005] tickets, whose values are reduced or multiplied over time, respectively, by simulating some small worlds of traders in the presence of whitewashers [M. Feldman, C. Papadimitriou, J. Chuang, I. Stoica, Free-riding and whitewashing in peer-to-peer systems, in: Proceedings of the ACM SIGCOMM Workshop on Practice and Theory of Incentives in Networked Systems, 2004, pp. 228236], a kind of free-riders who strategically leave and re-join the system with new identities. The results are compared with simulations of the MCS (Mutual Credit System), the category into which many existing currencies fall. © 2010 Elsevier B.V. All rights reserved.

Peer-to-peer complementary currencies can be powerful tools for promoting exchanges and building sustainable relationships among selfish peers on the Internet. i-WAT[1] is a proposed such currency based on the WAT System, a polycentric complementary currency using WAT tickets as its media of exchange. Participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanging messages signed in OpenPGP. This paper claims that the design of i-WAT is incentive-compatible as to protection against moral hazards, or threats caused by selfish peers because they may take advantage of the rules
such hazards are defused in i-WAT if the participants react against misbehaviors of others by pursuing their own benefits. A reference implementation of i-WAT has been developed in the form of an XMPP instant messaging client. We have been putting the currency system into practical use since June 2004. © Springer-Verlag Berlin Heidelberg 2006.

A peer-to-peer complementary currency can be a powerful tool for promoting exchanges that make use of underutilized computing resources in a trusted way. i-WAT[11] is a proposed such currency based on the WAT System[16], a polycentric complementary currency using WAT tickets as its media of exchange: participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanging messages signed in OpenPGP[3].
This paper proposes an extension to the design of i-WAT to facilitate trades. In particular we propose additional,"multiplication" tickets whose values increase over time. By deferring redemption of such tickets, the participants can receive the premium realized by increased debts of the issuers. A game-theoretical analysis shows that this feature is incentive-compatible: the issuers have no reason to strategically default despite the increased debts.
A reference implementation of i-WAT has been developed in the form of a plug-in for an XMPP[5][6] instant messaging client. We have been putting the currency system with the proposed feature into practical use.

Efforts have been put for electronization of complementary currencies (alternative forms of monetary media) in the hope that it would reduce their operational cost. However this paper argues that the problem is more inherent in the core design of MCS[7] (Mutual Credit System), the most common form of complementary currency today. By simulating a small world of 2,500 traders, we show that growing the number of free-riders in MCS has a paradoxical effect of increasing "welfare" (a "happiness" metric) of the community. Since there is no pressure to stop the growth of the bad users, it is difficult to sustain the soundness of the system without strong interventions from the operators of the system; we need alternatives to the alternatives.
We have proposed i-WAT[6] as an electronic descendant of the WAT System[10], a polycentric complementary currency using "WAT tickets" as its media of exchange. A simulation using the same model as above indicates that i-WAT users can sustain barter relationships even in the presence of free-riders by natural evasive actions to avoid risks.

A peer-to-peer complementary currency can be a powerful tool for promoting exchanges and building relationships on the Internet. i-WAT [1] is a proposed such currency based on the WAT System [2], a polycentric complementary currency using WAT tickets as its media of exchange: participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanging messages signed in OpenPGP [3]. This paper investigates an extension to the design of i-WAT to facilitate mutual help among peers in need. In particular, we investigate additional "reduction" tickets whose values are reduced over time. By deferring redemption of such tickets, the participants can contribute to reduce the debts of the issuers, and the issuers help participants by providing exchange media that accelerate spending. This paper describes in detail how incentive-compatibility is achieved by this extended design; we predict that the following properties will hold, which resulted from a game-theoretical analysis.
1. Rapid circulation, or a reduction ticket will typically circulate at high speed until its effective value reaches the scheduled minimum, and
2. Vanishment equilibrium, or the system will be most stable if the values of tickets are to be reduced down to zero.
A reference implementation of i-WAT has been developed in the form of a plug-in for an XMPP [4], [5] instant messaging client. We have been putting the currency system into practical use, to which the proposed feature has been added.

A P2P currency can be a powerful tool for promoting exchanges in a trusted way that make use of under-utilized resources both incomputer networks and in real life.
There are three classes of resource that can be exchanged in a P2P system: atoms (ex. physical goods by way of auctions), bits, (ex. data files) and presences (ex. time slots for computing resources such as CPU, storage or bandwidth). If these are equally treated as commodities, however the economy of the system is likely to collapse, because data files can be reproduced at a negligibly small cost whereas time slots for computing resources cannot even be stockpiled for future use.
This paper clarifies this point by simulating a small world of traders, and proposes a novel way for applying the "reduction over time" feature[14] of i-WAT[l 1], a P2P currency. In the proposed new economic order (NEO), bits are freely shared among participants, whereas their producers are supported by peers, being given freedom to issue exchange tickets whose values are reduced over time.

Efforts have been put for electronization of complementary currencies (alternative forms of monetary media) in the hope that it would reduce their operational cost. However this paper argues that the problem is more inherent in the core design of MCS[7] (Mutual Credit System), the most common form of complementary currency today. By simulating a small world of 2,500 traders, we show that growing the number of free-riders in MCS has a paradoxical effect of increasing "welfare" (a "happiness" metric) of the community. Since there is no pressure to stop the growth of the bad users, it is difficult to sustain the soundness of the system without strong interventions from the operators of the system; we need alternatives to the alternatives.
We have proposed i-WAT[6] as an electronic descendant of the WAT System[10], a polycentric complementary currency using "WAT tickets" as its media of exchange. A simulation using the same model as above indicates that i-WAT users can sustain barter relationships even in the presence of free-riders by natural evasive actions to avoid risks.

A peer-to-peer complementary currency can be a powerful tool for promoting exchanges and building relationships on the Internet. i-WAT [1] is a proposed such currency based on the WAT System [2], a polycentric complementary currency using WAT tickets as its media of exchange: participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanging messages signed in OpenPGP [3]. This paper investigates an extension to the design of i-WAT to facilitate mutual help among peers in need. In particular, we investigate additional "reduction" tickets whose values are reduced over time. By deferring redemption of such tickets, the participants can contribute to reduce the debts of the issuers, and the issuers help participants by providing exchange media that accelerate spending. This paper describes in detail how incentive-compatibility is achieved by this extended design; we predict that the following properties will hold, which resulted from a game-theoretical analysis.
1. Rapid circulation, or a reduction ticket will typically circulate at high speed until its effective value reaches the scheduled minimum, and
2. Vanishment equilibrium, or the system will be most stable if the values of tickets are to be reduced down to zero.
A reference implementation of i-WAT has been developed in the form of a plug-in for an XMPP [4], [5] instant messaging client. We have been putting the currency system into practical use, to which the proposed feature has been added.

Peer-to-peer complementary currencies can be powerful tools for promoting collaborations and building relationships on the Internet. i-WAT [1] is a proposed such currency based on WAT System [2], a polycentric complementary currency using WAT tickets as its medium of exchange. Participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanges of messages signed in OpenPGP [3]. This paper clarifies the trust model of i-WAT, and investigates how it is related with that of PGP [4]. To implement the model by dynamically building an appropriate web of trust (WOT), we claim that it would suffice if the behaviors of participants satisfy the following three properties: 1. mutual signing by knowing, or any two mutual acquaintances sign the public keys of each other, 2. mutual signing by participation, or the drawer and a user of an i-WAT ticket sign the public keys of each other, and 3. mutual full trust by participation, or the drawer and a user of an i-WAT ticket fully trust each other, and a recipient fully trust the corresponding user of a ticket, in the context of PGP public key signing. Likelihood of satisfaction of these properties is supported by the (dis)incentives imposed by the semantics of i-WAT. A reference implementation of i-WAT has been developed in the form of a Jabber [5] instant messaging client. We are beginning to put the currency system into practical use. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.

Peer-to-peer complementary currencies can be powerful tools for promoting collaborations and building relationships on the Internet. i-WAT [1] is a proposed such currency based on WAT System [2], a polycentric complementary currency using WAT tickets as its medium of exchange. Participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-WAT implements the tickets electronically by exchanges of messages signed in OpenPGP [3]. This paper clarifies the trust model of i-WAT, and investigates how it is related with that of PGP [4]. To implement the model by dynamically building an appropriate web of trust (WOT), we claim that it would suffice if the behaviors of participants satisfy the following three properties:
1. mutual signing by knowing, or any two mutual acquaintances sign the public keys of each other,
2. mutual signing by participation, or the drawer and a user of an i-WAT ticket sign the public keys of each other, and
3. mutual full trust by participation, or the drawer and a user of an i-WAT ticket fully trust each other, and a recipient fully trust the corresponding user of a ticket, in the context of PGP public key signing.
Likelihood of satisfaction of these properties is supported by the (dis)incentives imposed by the semantics of i-WAT. A reference implementation of i-WAT has been developed in the form of a Jabber [5] instant messaging client. We are beginning to put the currency system into practical use.

This paper proposes a barter currency system called i-WAT[12] to promote sustainable economy in peer-to-peer internetworking. i-WAT itself is a peer-to-peer system, without necessitating a central point of authority. It uses a digitally signed, electronic form of promissory note as the medium of exchange.
This paper illustrates how it should assist internetworking of peer-to-peer systems, and discusses, in particular how trust can be maintained in such a currency system.
Among other means, the current design of i-WAT allows the notes to be transported over Jabber[8, 9] instant messaging protocol. A prototype of an i-WAT checkbook has been developed as a plug-in for a Jabber client. We are beginning to experiment on the actual usage of the currency system using the checkbook as well as provisional web applications.

This paper proposes a resilient, alternative monetary system on the Internet called i-WAT, based on WAT System[l] which uses a form of promissory note as the medium of exchanging goods and services. i-WAT uses an electronic version of the note, ownership of which is transferred by exchanging messages signed in OpenPGP[2]. i-WAT can be used as the basis of various interpersonal/corporative transactions in the globally distributed computing environment. Specific applications being investigated include distributed consumer reports, an alternative copyright system and spam-free e-mail exchange. A prototype of an i-WAT checkbook has been developed as a plug-in for a Jabber[3] client. Experiments are ongoing.