Self-Escrowed Cash against User Blackmailing

  • Birgit Pfitzmann
  • Ahmad-Reza Sadeghi
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1962)


Protecting customer privacy is an important requirement when designing electronic cash systems. However, there is also concern that anonymous cash systems can be misused for criminal activities. Particularly blackmailing is in fact more severe in digital cash systems than in paper-based systems. This is because on the one hand the blackmailer is able to avoid physical contact and on the other hand there are no recognizable note numbers. To prevent such activities, several cash systems have been proposed where one or a collection of trustees can revoke the anonymity of a user. However, this also introduces a serious risk that this revocation ability is misused.

In this paper we show that the problem of user blackmailing can be solved without this risk. In our proposal, instead of a trustee, it is rather the blackmailed person who reveals the required information to trace extorted coins without compromising any of her secrets. We show how to derive such systems from concrete existing proposals for anonymityrevocable cash systems with passive trustee.

Key words

Escrowed Cash Fair Cash Digital Coin Anonymity Revocation Blackmailing Self-Escrow 


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  1. [BC93]
    Stefan Brands, David Chaum: Distance-Bounding Protocols; Eurocrypt’ 93, LNCS 765,Springer-Verlag, Berlin 1994, 344–359.Google Scholar
  2. [BGK95]
    Ernest Brickell, Peter Gemmell, David Kravitz: Trustee-based Tracing Extensions to Anonymous Cash and the Making of Anonymous Change; 6th ACM-SIAM Symposium on Discrete Algorithms (SODA) 1995, ACM ress, New York 1995, 457–466.Google Scholar
  3. [Bra94]
    Stefan Brands: Untraceable O.-line Cash in Wallet with Observers; Crypto’93, LNCS 773, Springer-Verlag, Berlin 1994, 302–318.Google Scholar
  4. [BP89]
    Holger Bürk, Andreas Pfitzmann: Digital Payment Systems Enabling Security and Unobservability; Computers & Security 8/5 (1989) 399–416.CrossRefGoogle Scholar
  5. [CFN90]
    David Chaum, Amos Fiat, Moni Naor: Untraceable Electronic Cash; Crypto’ 88, LNCS 403, Springer-Verlag, Berlin 1990, 319–327.CrossRefGoogle Scholar
  6. [Cha83]
    David Chaum: Blind Signatures for untraceable payments; Crypto’ 82, Plenum Press, New York 1983, 199–203.Google Scholar
  7. [Cha85]
    David Chaum: Security without Identi.cation: Transaction Systems to make Big Brother Obsolete; Communications of the ACM 28/10 (1985) 1030–1044.CrossRefGoogle Scholar
  8. [Cha89]
    David Chaum: Privacy Protected Payments-Unconditional Payer and/or Payee Untraceability; SMART CARD 2000: The Future of IC Cards, IFIP WG 11.6 Conference 1987, North-Holland, Amsterdam 1989, 69–93.Google Scholar
  9. [CMS96]
    Jan Camenisch, Ueli Maurer, Markus Stadler: Digital Payment Systems with Passive Anonymity-Revoking Trustees; ESORICS’ 96 (4th European Symposium on Research in Computer Security), LNCS 1146, Springer-Verlag,Berlin 1996, 33–43.CrossRefGoogle Scholar
  10. [CP93]
    David Chaum, Torben Pryds Pedersen: Wallet Databases with Observers; Crypto’92, LNCS 740, Springer-Verlag, Berlin 1993, 89–105.Google Scholar
  11. [CPS96]
    Jan Camenisch, Jean-Marc Piveteau, Markus Stadler: An Efficient Fair Payment System; 3rd ACM Conference on Computer and Communications Security, New Delhi, India, March 1996, ACM Press, New York 1996, 88–94.Google Scholar
  12. [DFTY97]
    George Davida, Yair Frankel, Yiannis Tsiounis, Moti Yung: Anonymity Control in E-Cash Systems; 1st International Conference on Financial Cryptography (FC’ 97), LNCS 1318, Springer-Verlag, Berlin 1997, 1–16.CrossRefGoogle Scholar
  13. [Fro96]
    A. Michael Froomkin: Flood Control on the Information Ocean, Living With Anonymity, Digital Cash, and Distributed Databases; Pittsburgh Journal of Law and Commerce 395, 1996. Available online at
  14. [FTY96]
    Yair Frankel, Yiannis Tsiounis, Moti Yung: “Indirect Discourse Proofs”: Achieving Efficient Fair O.-Line E-cash; Asiacrypt’96, LNCS 1163, Springer-Verlag, Berlin 1997, 287–300.Google Scholar
  15. [FTY98]
    Yair Frankel, Yiannis Tsiounis, Moti Yung: Fair O.-Line e-Cash Made Easy; Asiacrypt’ 98, LNCS 1514, Springer-Verlag, Berlin 1998, 257–270.Google Scholar
  16. [JY96]
    Markus Jakobsson, Moti Yung: Revocable and Versatile Electronic Money; 3rd ACM Conference on Computer and Communications Security, ACM Press, New York 1996, 76–87.Google Scholar
  17. [PP97]
    Holger Petersen, Guillaume Poupard: Efficient scalable fair cash with o.-line extortion prevention; 1st International Conference on Information and Communications Security (ICICS), LNCS 1334, Springer-Verlag, Berlin 1997, 463–477.CrossRefGoogle Scholar
  18. [PW97]
    Birgit Pfitzmann, Michael Waidner: Strong Loss Tolerance of Electronic Coin Systems; ACM Transactions on Computer Systems 15/2 (1997) 194–213.CrossRefGoogle Scholar
  19. [SN92]
    Sebastiaan von Solms, David Naccache: On Blind Signatures and Perfect Crimes; Computers & Security 11/6 (1992) 581–583.CrossRefGoogle Scholar
  20. [ST98]
    Aymeric de Solages, Jacques Traoré: An Efficient Fair O.-Line Electronic Cash System with Extensions to Checks and Wallets with Observers; 2nd International Conference on Financial Cryptography (FC’ 98), LNCS 1465, Springer-Verlag, Berlin 1998, 275–295.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Birgit Pfitzmann
    • 1
  • Ahmad-Reza Sadeghi
    • 1
  1. 1.Fachbereich InformatikUniversität des SaarlandesSaarbrückenGermany

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