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International Conference on Financial Cryptography and Data Security

FC 2016: Financial Cryptography and Data Security pp 43–60Cite as

Blindly Signed Contracts: Anonymous On-Blockchain and Off-Blockchain Bitcoin Transactions

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Part of the book series: Lecture Notes in Computer Science ((LNSC,volume 9604))

Abstract

Although Bitcoin is often perceived to be an anonymous currency, research has shown that a user’s Bitcoin transactions can be linked to compromise the user’s anonymity. We present solutions to the anonymity problem for both transactions on Bitcoin’s blockchain and off the blockchain (in so called micropayment channel networks). We use an untrusted third party to issue anonymous vouchers which users redeem for Bitcoin. Blind signatures and Bitcoin transaction contracts (aka smart contracts) ensure the anonymity and fairness during the bitcoin \(\leftrightarrow \) voucher exchange. Our schemes are practical, secure and anonymous.

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Notes

  1. 1.

    Our off-blockchain scheme is fast because it uses micropayment channel networks. It’s unclear how to retrofit prior work onto these networks, e.g., mapping Coinshuffle’s single atomic transaction onto the arbitrary graph topology of a micropayment channel network.

  2. 2.

    We assume that all transactions in our schemes are of 1 bitcoin value.

  3. 3.

    We could allow users to perform multiple payments (by using multiple Bitcoin addresses that belong to them) but this would reduce their anonymity and make our analysis more complex.

  4. 4.

    \(\mathcal {I}\) signs \( T _f\) to stop a malicious miner that learns \(\overline{\sigma }\) from stealing the bitcoin \(\mathcal {A}\) gives \(\mathcal {I}\).

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Acknowledgments

We thank Dimitris Papadopoulos, Ann Ming Samborski and the anonymous reviewers for comments on this draft. This work was funded by the National Science Foundation under grants 1012910 and 1350733.

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Authors and Affiliations

  1. Boston University, Boston, USA

    Ethan Heilman, Foteini Baldimtsi & Sharon Goldberg

Authors
  1. Ethan Heilman
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  2. Foteini Baldimtsi
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  3. Sharon Goldberg
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Corresponding author

Correspondence to Ethan Heilman .

Editor information

Editors and Affiliations

  1. Concordia University, Montreal, Québec, Canada

    Jeremy Clark

  2. University College London, London, United Kingdom

    Sarah Meiklejohn

  3. Université du Luxembourg, Luxembourg, Luxembourg

    Peter Y.A. Ryan

  4. Rice University, Houston, Texas, USA

    Dan Wallach

  5. Leibniz Universität Hannover, Hannover, Germany

    Michael Brenner

  6. New Jersey Institute of Technology, Newark, New Jersey, USA

    Kurt Rohloff

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© 2016 International Financial Cryptography Association

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Heilman, E., Baldimtsi, F., Goldberg, S. (2016). Blindly Signed Contracts: Anonymous On-Blockchain and Off-Blockchain Bitcoin Transactions. In: Clark, J., Meiklejohn, S., Ryan, P., Wallach, D., Brenner, M., Rohloff, K. (eds) Financial Cryptography and Data Security. FC 2016. Lecture Notes in Computer Science(), vol 9604. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-53357-4_4

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  • DOI: https://doi.org/10.1007/978-3-662-53357-4_4

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  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-662-53356-7

  • Online ISBN: 978-3-662-53357-4

  • eBook Packages: Computer ScienceComputer Science (R0)

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