A Survey of Electronic Micropayment Schemes Lovis J.I. Zenz advised - - PowerPoint PPT Presentation

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A Survey of Electronic Micropayment Schemes Lovis J.I. Zenz advised - - PowerPoint PPT Presentation

Sep 22, 2022 124 likes •369 views

Chair of Network Architectures and Services Department of Informatics Technical University of Munich A Survey of Electronic Micropayment Schemes Lovis J.I. Zenz advised by Richard von Seck Friday 12 th April, 2019 Chair of Network

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Chair of Network Architectures and Services Department of Informatics Technical University of Munich

A Survey of Electronic Micropayment Schemes

Lovis J.I. Zenz

advised by Richard von Seck Friday 12th April, 2019 Chair of Network Architectures and Services Department of Informatics Technical University of Munich

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Context: Electronic Micropayment Schemes

What is a micropayment?

  • “Payments worth a few pennies” [1]
  • varying upper bounds
  • never more than 10$ [6]
  • L. Zenz — Electronic Micropayment Schemes

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Context: Electronic Micropayment Schemes

Where are micropayments relevant?

  • handling free-riders in P2P anonymity systems [2]
  • one-time webpage access [7]
  • other one-time services [3]
  • access to financial services in developing countries [8]
  • L. Zenz — Electronic Micropayment Schemes

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Context: Electronic Micropayment Schemes

How do micropayment schemes differ from common payment systems like PayPal?

  • reduced cost
  • less broker involvement
  • L. Zenz — Electronic Micropayment Schemes

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Categorization: Basic Characteristics of Micropayment Schemes

Based on which properties can micropayment schemes be distinguished?

  • online vs. offline
  • centralized vs. decentralized
  • credit-based vs. debit-based
  • L. Zenz — Electronic Micropayment Schemes

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Basic Micropayment Scheme: PayWord

What is PayWord?

  • proposed by Rivest & Shamir in 1997 [7]
  • employs one-dimensional hashing (100 times faster than RSA signature verification)
  • employs public key encryption
  • centralized, offline, credit-based
  • roles: brokers, vendors, and users
  • L. Zenz — Electronic Micropayment Schemes

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Basic Micropayment Scheme: PayWord

How are payments handled by PayWord?

  • 1. user generates PayWord chain (caps maximum amount of payments in prior)
  • 2. vendor receives single PayWords from user
  • 3. vendor provides service
  • 4. repeat 1. - 3. several times during day
  • 5. vendor forwards PayWords to broker at end of day
  • 6. broker verifies PayWords and conducts transactions
  • L. Zenz — Electronic Micropayment Schemes

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Basic Micropayment Scheme: PayWord

How is a PayWord chain generated?

  • 1. define amount of needed PayWords → n ∈ N
  • 2. choose a hash function and a random PayWord appropriately → wn
  • 3. calculate remaining PayWords → ∀i ∈ N, 0 ≤ i ≤ (n − 1) : wi = h(wi+1)
  • L. Zenz — Electronic Micropayment Schemes

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Basic Micropayment Scheme: PayWord

How are payments handled by PayWord?

  • 1. user generates PayWord chain (caps maximum amount of payments in prior)
  • 2. vendor receives single PayWords from user
  • 3. vendor provides service
  • 4. repeat 1. - 3. several times during day
  • 5. vendor forwards PayWords to broker at end of day
  • 6. broker verifies PayWords and conducts transactions
  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

What is PPayWord?

  • proposed by Mu, Varadharajan, and Lin in 1997 [4]
  • adds salting techniques to PayWord
  • third of three schemes that are based on each other
  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

How does PPayWord extend PayWord?

  • SPayWord: set of salts → shared secret

wi = h(wi+1, Si+1) with Si = h(Si+1, P, g) where g = h(gC(dj), V)

  • UPayWord: reverse generation → unlimited PayWords
  • PPayWord: shared payment commitment → loss recovery
  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

How does PPayWord extend PayWord?

  • SPayWord: set of salts → shared secret
  • UPayWord: reverse generation → unlimited PayWords

wi+1 = h(wi, Si+1) with Si = Ri ⊕ h(P, g) where Ri+1 = h(Ri, P) and g = h(gC(dj), V)

  • PPayWord: shared payment commitment → loss recovery
  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

How does PPayWord extend PayWord?

  • SPayWord: set of salts → shared secret
  • UPayWord: reverse generation → unlimited PayWords
  • PPayWord: shared payment commitment → loss recovery

zi = h(wi ⊕ Xi) with wi = h(i, P) ⊕ Si + 1 and Xi = h(gC(dj), V, i)

  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

What are MDHC?

  • proposed by Nguyen in 2006 [5]
  • multi-dimensional hash chains
  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

How are MDHC generated?

  • 1. choose/generate a one-way hash chain → x0 = h1(x1) = ... = hn−1(xn−1) = hn(xn)
  • 2. employ one-way accumulators

y = h1(h2(...(hm−1(hm(x))))) to generate a multi-dimensional hash chain: X0 = hn1

1 (hn2 2 (...(h nm−1 m−1 (hnm m (XN)))))

  • L. Zenz — Electronic Micropayment Schemes

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Extensions: Micropayment Schemes that Are Based on PayWord

How can MDHC improve PayWord?

  • storage capacity: N − 1 = (n + 1)m − 1
  • storage computational complexity: O(N) = O(nlogn+1((n + 1)m) → O(log2N) for n = 1
  • L. Zenz — Electronic Micropayment Schemes

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Alternatives: Micropayment Schemes that Are Not Based on PayWord

What is the Peppercoin method?

  • proposed by Rivest in 2004
  • aggregation of several micropayments in one macropayment
  • L. Zenz — Electronic Micropayment Schemes

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Alternatives: Micropayment Schemes that Are Not Based on PayWord

How does the Peppercoin method work?

  • session-level aggregation, aggregation by intermediation, and universal aggregation
  • brokers (banks) as buffers
  • L. Zenz — Electronic Micropayment Schemes

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Alternatives: Micropayment Schemes that Are Not Based on PayWord

What is DAM?

  • proposed by Chiesa et al. in 2017
  • Bitcoin as inspiration
  • L. Zenz — Electronic Micropayment Schemes

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Alternatives: Micropayment Schemes that Are Not Based on PayWord

How does DAM work?

  • decentralized anonymous payments
  • probabilistic payments
  • private coin deposits
  • L. Zenz — Electronic Micropayment Schemes

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Conclusion: Overview of Advantages and Disadvantages

Based on which criteria can micropayment schemes be evaluated?

  • performance
  • efficiency
  • security
  • anonimity
  • L. Zenz — Electronic Micropayment Schemes

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Conclusion: Overview of Advantages and Disadvantages

How do different micropayment schemes look in comparison? Name Performance Efficiency Security Anonymity Peppercoin + simplified signing + aggregation method not in scope not in scope DAM + offline + offline

  • decentralized

+ decentralized + probabilistic payments

  • double spending

+ anonymous payments + blacklist require- ment + private coin deposit S2 + offline + offline + centralized

  • centralized

Scheme + MDHC + MDHC

  • RSA modular ex-

ponentiation PPayWord + offline + offline + centralized

  • centralized

+ shared secret

Table 1: Overview of Different Micropayment Schemes

Table 1 shows different micropayment schemes in comparison.

  • L. Zenz — Electronic Micropayment Schemes

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Bibliography

[1]

  • A. Chiesa, M. Green, J. Liu, P

. Miao, I. Miers, and P . Mishra. Decentralized Anonymous Micropayments. In J.-S. Coron and J. B. Nielsen, editors, Advances in Cryptology – EUROCRYPT 2017, pages 609–642, Cham, 2017. Springer International Publishing. [2]

  • D. Figueiredo, J. Shapiro, and D. Towsley.

Incentives to Promote Availability in Peer-to-Peer Anonymity Systems. 13th IEEE International Conference on Network Protocols (ICNP’05), pages 12–121, 2005. [3]

  • D. Gille.

A TRANSACTION COST ANALYSIS OF MICROPAYMENTS IN MOBILE COMMERCE. Journal of Information and Organizational Sciences, 29(1):25–31, 2005. [4]

  • Y. Mu, V. Varadharajan, and Y.-X. Lin.

New micropayment schemes based on Pay Words. In V. Varadharajan, J. Pieprzyk, and Y. Mu, editors, Information Security and Privacy, pages 283–293, Berlin, Heidelberg,

  • 1997. Springer Verlag.

[5]

  • Q. S. Nguyen.

Multi-Dimensional Hash Chains and Application to Micropayment Schemes. In Ø. Ytrehus, editor, Coding and Cryptography, pages 218–228, Berlin, Heidelberg, 2006. Springer Berlin Heidelberg. [6]

  • R. L. Rivest.

Peppercorn Micropayments. Financial Cryptography, pages 2–8, 2004. [7]

  • R. L. Rivest and A. Shamir.

PayWord and MicroMint: Two Simple Micropayment Schemes. Lecture Notes in Computer Science, 1189:69–87, 1997.

  • L. Zenz — Electronic Micropayment Schemes

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Bibliography

[8]

  • N. Wishart.

Micro-Payment Systems and Their Application to Mobile Networks. infoDev / World Bank, Washington, DC, 2006.

  • L. Zenz — Electronic Micropayment Schemes

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