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Risk Management for E-Cash Systems with Partial Real-Time Audit

  • Yacov Yacobi
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1648)

Abstract

We analyze “coin-wallet” and “balance-wallet” under partial real-time audit, and compute upper bounds on theft due to the fact that not all the transactions are audited in real time, assuming that every- thing else is perfect. In particular, we assume that the audit regime holds for innocent players. Let v be the maximum allowed balance in a wallet, 0 ≤ μ ≤ 1 be the fraction of transactions that are audited in real time in an audit round that includes overall n transactions. Assume one unit transactions. We show that for μ << 1 the upper bound on expected theft for coin-wallet is \( \frac{\upsilon } {{e^{\mu ^2 \upsilon } - 1}} \) (which if v << μ−2 becomes \( (e^{\mu ^2 } - 1)^{ - 1} \)), while for plausible parameter choice the bound for a balance-wallet is O(exp(v 2/n)). This last bound can become huge in some cases, implying that partial audit, while suitable for coin-wallets with low denomination coins, may be too risky for balance-wallet. Some implications to the design of anonymous and non-anonymous systems are discussed.

Keywords

Cryptography e-cash randomized-audit risk-management economy 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Yacov Yacobi
    • 1
  1. 1.Microsoft ResearchOne Microsoft WayRedmond

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