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Journal Pre-proofs A 2020 perspective on “A fair contract signing protocol with blockchain sup‐ port” Josep-Lluis Ferrer-Gomila, M. Francisca Hinarejos PII: DOI: Reference:

S1567-4223(20)30058-2 https://doi.org/10.1016/j.elerap.2020.100981 ELERAP 100981

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Electronic Commerce Research and Applications

Received Date: Revised Date: Accepted Date:

29 January 2020 10 May 2020 14 May 2020

Please cite this article as: J-L. Ferrer-Gomila, M. Francisca Hinarejos, A 2020 perspective on “A fair contract signing protocol with blockchain support”, Electronic Commerce Research and Applications (2020), doi: https:// doi.org/10.1016/j.elerap.2020.100981

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we expecElectronic Commerce Research and Applications ## (2020) ######

A 2020 perspective on “A fair contract signing protocol with blockchain support” Josep-Lluis Ferrer-Gomila, M. Francisca Hinarejos* Department of Mathematics and Computer Science, University of the Balearic Islands (UIB), Spain _______ *

Corresponding author. Email addresses: [email protected] (J.L. Ferer-Gomila), [email protected] (M.F. Hinarejos). _________________________________________________________________________________________________________________ ________ ____________ ARTICLE INFO __________________________________________________ Keywords: Blockchain Contract signing Cryptocurrency Digital Economy Fair exchange Fintech Trust-free system

ABSTRACT _________________________________________________ ________ _____________________ The development of the blockchain with its different irtues (d centra ized trust, auditability, accessibility, immutability of their operations, etc.) has allowed centr ized applications to find a solution to their problems, such as trust, scalability, etc. One of these applications is he electronic signature of contracts which is a key point for the deployment of electronic transa tions in he fie of e-commerce. We have used the blockchain for contract-signing to avoid the use of cent alized trus ed third-parties, in a simple way, and where the use of any blockchain solution, allowing data to e publishe at a reasonable cost, can be easily integrated in our proposal, involving Bitcoin-based solutions (e. , Lite oin or Dash) or Ethereum. Our results can help other authors to consider more factors, and not ju t the te hnological aspects, when selecting a blockchain solution.

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Although the origin and implementation of Bitcoin dates back to 2008 and 2009, it is in the 2010s decade when we can say tha the e actually was a burst of blockchain-based cryptocurrencies technolog innovation. The main concern was to manage doubl -spending without losing anonymity and without using the services of a trusted third-party (TTP). A large number of publications and proposals have been devoted to research on blockchain consensus mechanisms o ensure that they are secure and efficient. This is what led to the emergence of a myriad of blockchain-based cryptocurren ies. Notable among them is Ethereum, which represented a pa digm shift, as it established the concept of executing smart con acts on the blockchain. In the field of electronic signatur of ntracts, previous solutions required the existence and ossible involvement of a TTP to guarantee fairness. This was not wit out problems though, as the parties involved had to agree o a TTP th t would be trusted by all of them. On the other hand, it s not easy to design protocols in which the possible bad behavior of a TTP can be verified effectively and adequately. The main contributi n of Ferrer-Gomila et al. (2019) was to demonstrate that with imple use of the blockchain the participation of a TTP can be supp essed o achieve the requirement of fairness in the electronic ignature of contracts. In addition to thi main contribution for contract signing, we provided in Ferrer omila et al. (2019) an analysis of the economic cost of our proposal. We would like to emphasize that blockchainbased solutions may involve a cost (depending on the type of blockchain sed, scenario, type of participants, etc.), so it is important to evaluate the possible cost required for participants. This cost arises from several factors that must be taken into account in this evaluation. For example, the trading of cryptocurrencies that are usually associated with blockchain networks, the complexity of the code executed (e.g., smart contracts in Ethereum), the length of the data to be published, etc. Although a solution may be technically feasible, it still may incur in costs that users may not be willing to assume. However, it is also true that it could reduce costs for companies, or at least these costs would be less than those associated with the full deployment of the solution without the blockchain. Therefore, solutions based on blockchain require a proper analysis of the

bloc chain platform to be used and the costs associated with that. We think that these are important points that should be included in any ew proposal. Since the publication of Ferrer-Gomila et al. (2019), no publication or "commercial product" related to the electronic signature of contracts with the support of the blockchain has been observed. But the electronic signature of contracts is part of a set of services labeled as fair exchange of value: two or more parties wish to exchange an item they own for another that owns the other party, so that in the end all parties obtain the desired item or none of them obtains it. Some examples of this type of services are: certified email (exchange of an email for an acknowledgment of receipt), payment by receipt (exchange of a payment for a receipt of the payment made), or payment for a digital product (exchange of a payment for a product that can be supplied electronically). Within this area, to which the contract signing belongs, we found especially interesting to research in the field of certified email. The paper version of this service is especially useful in public administration, but it also has been widely used by companies. There are multiple proposals (Genai et al, 2005) (Draper et al, 2010) for the corresponding electronic version, but the vast majority of them require the participation of a trusted third party (which hinders their commercial success). On the other hand, there have been some recently-published proposals related to the article that we published in Electronic Commerce Research and Applications, where the provided security is based on the use of the blockchain, partially as a public registry (Hinarejos et al., 2019) or completely as a private solution based on the blockchain infrastructure (McAfee, 2015). Once we verified that the blockchain is useful for achieving fairness for contract signing without the need for a TTP, after the publication of Ferrer-Gomila et al. (2019), we have continued to explore improvements in this line. On the one hand, we decided to use another blockchain different from Bitcoin, and more specifically Ethereum. The smart contracts of this blockchain allow us to provide more versatile solutions, as we do not have the restrictions of the Bitcoin blockchain (which only allows the publication of a very small amount of information, and does not allow the execution of complex code). On the other hand, we have been working on the design of a

protocol for the electronic signature of contracts in case there are more than two signatories. Finally, we have already made proposals for certified email (based on blockchain) (Hinarejos et al., 2019). Now we are designing a protocol for the case in which the same certified mail must be sent to multiple recipients. By the end of the 2010s, the publication of multiple proposals with alternative uses of the blockchain had occurred beyond its use for financial transactions. During the next decade, the 2020s, we expect to see an explosion of proposals for applications of blockchain technology in different fields. For example, the blockchain is impacting multiple scenarios now: energy distribution, intellectual property protection, health care, etc. We are living in a time when blockchain seems like a panacea to address a lot of problems, albeit surely in an exaggerated way. In any case, it is true that the blockchain can be very useful when it is necessary (and beneficial) to have a public record of actions carried out by parties involved in electronic transactions. The field of e-commerce should not be left out of this new revolution. In fact, we must not forget that the first application (we could almost talk about the birth or rebirth) of the blockchain was as electronic money – Bitcoin, and that payments are a key element of e-commerce.

Acknowledgment. This work was supported by the European Social Fund (ERDF) and the Spanish Government (Ministerio de Economia, Industria y Competitividad (MINECO) - Agencia Estatal de Investigación (AEI)) under projects RTI2018-097763-B-I00 and RED2018-102321-T. References Draper-Gil, G., Ferrer-Gomila, J. L., Hinarejos, M. F., & Tauber, A., 2014. An optimistic certified e-mail protocol for the current Internet e-mail architecture. In 2014 IEEE Conference on Communications and Network Security (pp. 382-390). https://doi.org/10.1109/CNS.2014.6997507 Ferrer-Gomila, J.L., Hinarejos, M.F., Isern-Deyà, A.P., 2019. A fair contract signing protocol with blockchain support. Electron. Comm. Res Appl , 100869. https://doi.org/10.1016/j.elerap.2019.100869 Gennai, F., Martusciello, L., & Buzzi, M., 2005. A certif email system for the public administration in Italy. In IADIS International Conference WWW/Internet (Vol. 2, pp. 143-147). https://doi.org/10.1007/978-3-642-1817 13 Hinarejos, M.F., Ferrer-Gomila, J.L., Huguet i Rotger, L. 2019. A solution for secure certified electronic mail using blockchain as a ecure mess ge board. IEEE Access 7, 31330-31341. https://doi.org/10.1109/ACCESS 019.2902174 McAfee, J., 2015. Swiftmail. https: /joh mcafe wif mail.com/ (accessed 3 May 2020).

https://doi.org/10.1016/elerap.2020/###### Received 10 January 2020. Received in revised form 14 January 2020. Accepted 15 January 2020. Available online ## MONTH 2020 1567-4223 © 2020 Elsevier B.V. All rights reserved.

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financ al interests/personal relationships which may be considered as potential competing interests:...