Electronic Cash Scheme Research Articles

A Proposal for a Canadian CBDC

Undoubtedly inspired by recent advances in technology-driven payment systems such as mobile payment systems, cryptocurrencies, and blockchain technologies, recent years have seen central banks worldwide explore the possibility of issuing digital forms of fiat money called central bank digital currencies or CBDCs. A thoughtfully designed CBDC can help satisfy numerous policy objectives, improve economic efficiency and inclusivity, and serve as a platform for economic innovation. However, the vast CBDC design landscape, coupled with its potential to massively disrupt the financial system and broader economy, warrants caution, calling for a careful and methodical analysis of various designs' strengths, weaknesses, and risk profiles. At this time, the Bank of Canada (BoC) has not committed to issuing a CBDC; nevertheless, it does rank among the more than 80% of central banks globally who, according to a recent survey by the Bank for International Settlements (BIS), are at least contingency planning for the eventuality of doing so. This report details and analyzes the authors' vision for a hypothetical BoC-issued retail CBDC for use in the Canadian context, taking into account both, the `business case' for its adoption from the perspective of BoC, policymakers, the financial services industry, and the Canadian economy more generally and how its widespread adoption would impact ordinary Canadians. The design considered in this report leverages a mix of distributed ledger technologies (DLTs} and electronic cash (`e-cash') schemes with advanced cryptographic primitives. The confluence of these building blocks results in a scalable, resilient, privacy-centric, and universally accessible design that strives to bring added value (a Pareto improvement) for all stakeholders in Canada. In light of the abundance of CBDC designs in circulation, this report emphasizes aspects and implications of the design specifically tailored for Canada, such as ensuring universal access for remote communities and strong privacy protections consistent with Canada's role as a world leader in civil liberties and human rights. Likewise, some core aspects of the proposed architecture reflect characteristics of Canadian law and the Canadian financial system, which may differ substantially from other countries.

A fair offline electronic cash scheme with multiple-bank in standard model

ABSTRACTOffline electronic cash is a new and well-acknowledged type of e-cash scheme that can release the bank from participating in every spending protocol. However, it is still an unsolved problem to design a secure and efficient fair offline e-cash scheme. Considering this problem, in this paper, we have proposed a fair offline electronic cash scheme with multiple banks in pairing-based instantiation. We adopt Groth–Sahai non-interactive zero-knowledge proof technology in our scheme, to design non-interactive e-cash transactions. Additionally, inspired by Water’s group signature, our solution supports not only multiple users, but also users with accounts in different banks. Moreover, our scheme has efficient double-spending checking and a fair control mechanism. We have formally defined the security properties of the scheme in a standard model, and provided the detailed security proofs of the security properties concerning chosen ciphertext attack (CCA) anonymity, unforgeability and traceability. Analysis and comparison show that our scheme has advantages both in security and in efficiency.

Numerical Method for Evaluating E-Cash Security

Security evaluations of electronic cash (e-cash) schemes usually produce an abstract result in the form of a logical proof. This paper proposes a new method of security evaluation that produces a quantitative result. The evaluation is done by analyzing the protocol in the scheme using the Markov chain technique. This method calculates the probability of an attack that could be executed perfectly in the scheme’s protocol. As proof of the effectiveness of our evaluation method, we evaluated the security of Chaum’s untraceable electronic cash scheme. The result of our evaluation was compared to the evaluation result from the pi-calculus method. Both methods produced comparable results; and thus, both could be used as alternative methods for evaluating e-cash security.

Robust off‐line e‐cash scheme with recoverability and anonymity revocation

AbstractRecently, electronic cash has become a hot topic issue with the concurrent sustainable growth of electronic commerce. In practice, however, most current electronic cash schemes do not satisfy all necessary requirements. In this paper, we point out flaws in the Fan et al. scheme and based on their scheme, propose a new off‐line e‐cash scheme. We use an ElGamal signature instead of the chameleon hash function to revise the problem of forgeability and reusability in the original scheme. We use an expiration date to improve the management efficiency of the bank's database and resolve the lost privacy problem in the recovery protocol. Our proposed scheme provides security without increasing computation and communication costs compared with the Fan et al. scheme. Copyright © 2016 John Wiley & Sons, Ltd.

An Untraceable Off-Line Electronic Cash Scheme without Merchant Frauds

In an electronic cash scheme, there are three participants, the bank, the spender and the merchant. First, a spender opens an account in a bank. Then, he withdraws electronic cash from his account and pays it to a merchant. After checking the electronic cash’s validity, the merchant accepts it and deposits it to the bank. There are a number of requirements for an electronic cash scheme, such as, anonymity, unforgeability, unreusability, date attachability, divisibility, transferability and portability. In this paper, we show a recently proposed electronic cash scheme is suffering from some faults in anonymity, expiration date and merchant frauds. To improve the scheme, we propose a new untraceable off-line electronic cash scheme and give a security analysis for it.

Secure Electronic Cash Scheme with Anonymity Revocation

In a popular electronic cash scheme, there are three participants: the bank, the customer, and the merchant. First, a customer opens an account in a bank. Then, he withdraws ane-cash from his account and pays it to a merchant. After checking the electronic cash’s validity, the merchant accepts it and deposits it to the bank. There are a number of requirements for an electronic cash scheme, such as, anonymity, unforgeability, unreusability, divisibility, transferability, and portability. Anonymity property of electronic cash schemes can ensure the privacy of payers. However, this anonymity property is easily abused by criminals. In 2011, Chen et al. proposed a novel electronic cash system with trustee-based anonymity revocation from pairing. On demand, the trustee can disclose the identity fore-cash. But, in this paper we point out that Chen et al.’s scheme is subjected to some drawbacks. To contribute secure electronic cash schemes, we propose a new offline electronic cash scheme with anonymity revocation. We also provide the formally security proofs of the unlinkability and unforgeability. Furthermore, the proposed scheme ensures the property of avoiding merchant frauds.

Study and Design on Electronic Cash System Security Architecture

The rapid development of electronic financial services, attendant come an increasingly serious network security problem, especially electronic cash exchange network security issues facing the urgent need to resolve. In this paper, electronic cash scheme detailed research and analysis, and then design a secure electronic cash system based on an improved theory of electronic cash scheme, it includes detailed electronic payment requirements analysis, system design, e-commerce payment system design, server design and client design. Finance and electronics industry combining electronic financial system, if they can effectively solve the security issues, I believe it can be quickly developed.

Secure untraceable off-line electronic cash system

Eslami and Talebi (2011) [25] proposed an untraceable electronic cash scheme and claimed that their scheme protects the anonymity of customers, detects the identity of double spenders and provides the date attachability of coins to manage the bank database. In this paper, illustrating Eslami and Talebi’s scheme, as one of the latest untraceable electronic cash schemes, and showing its weaknesses (in fulfilling the properties of perceptibility of double spender, unforgeability and date attainability of coins) and its faults (related to exchange protocol), we propose a new untraceable electronic cash scheme which is immune to the weaknesses of the former. Our scheme contains anonymity, double-spending detection, unforgeability and date attachability properties and prevents forging. To do this, we described a special construction which injects the expiration date and the identity of the customer onto the coin and detects the identity in the case of double spending. Lastly, we show that the efficiency of our scheme is comparable with other schemes.

Two New Electronic Cash Schemes Based on Elliptic Curve

Two secure, high-efficient and feasible e-cash schemes are proposed in this thesis based on elliptic curve by using blind signature system, the schemes are completed by three protocols, namely, withdrawal protocol, payment protocol and deposit protocol. The two schemes make advantage of blind parameter, namely, after cash is received by Bank, cash is also hardly connected with the signature at some times. They are simple and easily realized. The elliptic curve cryptographic algorithm is adopted in the scheme, the length of the private key is short, and its efficiency and strength is significantly higher than e-cash scheme based on RSA signature proposed by D.Chaum. There is no effective solution to the elliptic curve discrete logarithm problem (ECDLP), therefore, the schemes are safe.

A proxy blind signature scheme and an off-line electronic cash scheme

To support withdrawing and storing money from all levels of the bank for the customers in the real world, in this paper, we propose a proxy blind signature scheme and an off-line e-cash scheme based on the new proxy blind signature scheme. The proposed proxy blind signature is proven secure in the random oracle model under chosen-target computational Diffie-Hellman assumptions, and the e-cash scheme can satisfy the security requirements of unforgeability, anonymity, and traceability.

A secure electronic cash based on a certificateless group signcryption scheme

Many certificateless schemes have been proposed for different purposes, but as for as their applications in any electronic cash schemes there is still a lot of potential for strengthening the security aspect, and this paper is an attempt towards this. In this paper we propose a new type certificateless scheme which is applied for group oriented signcryption rather than a signature without using bilinear pairing, then a new E-cash system has been presented based on the proposed scheme. The salient feature of the proposed scheme is that any signcrypter of a group can signcrypt a document with the group manager and send it to the verifier. The verifier verifies the authenticity of the signcrypted text by using the group’s public parameters and cannot link a signcrypted text to the corresponding signcrypter. However, even the group manager or any signcrypter of that group alone cannot produce a valid signcrypted text. In case of any legal dispute, such as no repudiation of the signature, the group manager has the ability to reveal the identity of the signcrypter. The proposed scheme is secure against the indistinguishably chosen cipher text attack (IND-CCA). Unlinkability, unforgeability and traceability and its security are based on the two computationally hard problems, the Computational Diffie–Hellman Problem (CDHP) and Discrete Logarithmic Problem (DLP). The new scheme’s security analysis clearly suggests that it is very reliable to be used in security vulnerable applications in real life.

A New E-cash Scheme Based on a Trapdoor Hash Function

As online shopping has become more popular because of recent changes in consumption patterns, many electronic cash schemes have proposed. Electronic cash schemes generally utilize public key algorithms to maintain electronic cash security. However, public key algorithms use many computation resources, and make electronic cash schemes inefficient for mobile devices to compute. Furthermore, the denominations of electronic cash are fixed, and the electronic cash spending date is hard to record. It will cause the lack of flexibility while applying. This research proposes a new electronic cash scheme that utilizes trapdoor hash function technology. The proposed scheme not only allows users to apply for desired denominations of electronic cash and to record transaction dates, but also decreases calculation costs, that is, our scheme can be implemented efficiently in all mobile devices.

A critique of “A novel electronic cash system with trustee-based anonymity revocation from pairing,” by Chen, Chou, Sun and Cho (2011)

This brief critique discusses a recent article by Chen et al. (2011) published in the journal. The authors proposed an electronic cash (e-cash) scheme with trustee-based anonymity revocation from pairing. I found that there are a couple issues that are not properly addressed. (1) The first flaw is that a bank can trace an e-cash payer easily and obtain the payer’s license for illegal usage because the related blind factor that is chosen is fixed, and thus, it is not properly removed from the e-cash in the authors’ scheme. (2) The second flaw is that it is possible for someone to dishonestly cooperate with an honest bank’s customer to defraud the honest bank, and this person’s identity cannot be traced.

Cryptanalysis of an Off-Line Electronic Cash Scheme Based on Proxy Blind Signature

Proxy blind signature is an important cryptographic primitive and plays an essential role in construction of the electronic cash (e-cash). Recently, Tan (2001, An offline electronic cash scheme based on proxy blind signature. Comput. J., 54, 505–512) proposed a new proxy blind signature scheme and applied it to electronic cash. The scheme was claimed as being provably secure under the Discrete Log assumption, DBDH assumption and Chosen–Target CDH assumption in the random oracle model. In this paper, we show that Tan's proxy blind signature scheme is insecure by demonstrating several attacks in which a malicious original signer can forge both valid proxy signature keys of arbitrary proxy signers and a proxy blind signature on an arbitrary message with respect to any proxy signer directly. We also discuss some weaknesses in the e-cash scheme proposed by Tan.

An Off-line Electronic Cash Scheme Based on Proxy Blind Signature

In a proxy signature scheme, the proxy signer generates a signature on a message. By the combination of a blind signature with a proxy signature, a proxy blind signature permits the proxy signer produce a blind signature on a message. In this paper, a proxy blind signature scheme based on bilinear pairings is proposed. The proxy blind signature scheme is proved secure upon the discrete logarithm assumptions, decisional bilinear Diffie–Hellman assumptions and Chosen-Target computational Diffie–Hellman assumptions in the Random Oracle Model. In the real world, the customers can withdraw and store money from all levels of the bank. On the basis of the new proxy blind signature, this manuscript proposed an electronic cash (e-cash) scheme. The e-cash scheme can provide unforgeability of e-cash, anonymity of honest customers and efficient traceability of double spending.

A new untraceable off-line electronic cash system

Digital content transactions through e-commerce will grow tremendously in the coming years. In this respect, well-designed electronic payment schemes and high-quality digital contents are two critical factors. Untraceable electronic cash schemes make it possible for customers to pay the e-cash to the merchants through communication networks under privacy protection. Therefore, there is a need to invent new electronic payment protocols with strong cryptographic algorithms that will eventually replace present day paper-based cash schemes. There have been two types of electronic cash schemes, namely on-line and off-line. In general off-line schemes are more efficient than on-line ones. The two fundamental issues with any off-line electronic cash scheme have been the detection of double-spending and provision of anonymity. This paper proposes a new untraceable off-line electronic cash scheme which can maintain anonymity and double spender detection and possesses strong fraud control capabilities. Moreover, the proposed scheme attaches expiration date to coins so that the banking system can manage its databases more efficiently. The scheme is based on cryptographic techniques such as ElGamal and blind signatures. The coins produced by the scheme can be transferred through computer networks into storage devices and vice versa so that portability is assured.

Optimized Electronic Cash Scheme with Fast Public Key Algorithm

In the paper, we analyzed the system optimization algorithms in e-cash (electronic cash) by improving the efficiency of e-cash for software and hardware application. As for the fast asymmetric cryptography algorithms in e-cash scheme, we presented basic interactive protocols based on discrete logarithm cryptosystem. In the protocol, the interacting algorithms achieve authenticated encryption in secret transmission algorithms, the verification of signature and transmission of secret message can be fulfilled in a single algorithm, and therefore the complexity of authentication algorithms in e-cash scheme is greatly reduced. As a comparison with traditional e-cash schemes, we presented an optimized e-cash scheme based on ECC (Elliptic Curves Cryptosystem). The cryptography algorithms of the scheme make full use of the superiority of ECC fast algorithms, thus the optimized e-cash scheme effectively avoids illegal distribution of e-cash and generalized forgery attack on system parameters with less system overheads.

Distributed architectures for electronic cash schemes: a survey1

The volume of E-commerce transactions has considerably increased in the last several years. One of the most important aspects of such progress is the efforts made to develop and deploy dependable and secure payment infrastructures. Among these infrastructures is electronic cash, which is an attempt to reproduce the characteristics of paper cash in online transactions. Electronic cash schemes have so far been the purpose of a significant amount of research work. Although real-life deployments of such schemes are expected to take place in highly distributed environments, limited attention has been paid in the literature on underlying architectural issues. So far the focus has mostly been on addressing only security issues. However, for real-life deployment, distributed processing criteria such as performance, scalability and availability are of prime importance. In this paper, through a survey of the literature, we identify and analyse the different distributed architectural styles underlying existing e-cash schemes. We discuss the strengths and limitations of these architectures with respect to fundamental system distribution criteria. In light of such discussion, we make some recommendations for designing effective distributed e-cash systems from an architectural perspective.

ID-Based Fair Off-Line Electronic Cash System with Multiple Banks

ID-based public key cryptography (ID-PKC) has many advantages over certificate-based public key cryptography (CA-PKC), and has drawn researchers' extensive attention in recent years. However, the existing electronic cash schemes are constructed under CA-PKC, and there seems no electronic cash scheme under ID-PKC up to now to the best of our knowledge. It is important to study how to construct electronic cash schemes based on ID-PKC from views on both practical perspective and pure research issue. In this paper, we present a simpler and provably secure ID-based restrictive partially blind signature (RPBS), and then propose an ID-based fair off-line electronic cash (ID-FOLC) scheme with multiple banks based on the proposed ID-based RPBS. The proposed ID-FOLC scheme with multiple banks is more efficient than existing electronic cash schemes with multiple banks based on group blind signature.

Provably Secure Untraceable Electronic Cash against Insider Attacks

Although a great deal of research has been done on electronic cash schemes with blind multisignatures to prevent an insider attack, there is no discussion of a formal security model in the literature. Firstly we discussed the security model of e-cash schemes based on the blind multisignature scheme against a (restricted) attack model and proposed a concrete scheme proven to be secure in the model [1]; however, this attack model disallows an attacker from corrupting an issuing bank and shops in the forgery game. In this paper, first, we reconsider the security model to remove the restriction of the attack model. Second, we propose a new untraceable e-cash scheme with a blind multisignature scheme and prove that the proposed scheme is secure against the (non-restricted) attacks under the DDH assumption in the random oracle model.