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Paper: Expected-Time Cryptography: Generic Techniques and Applications to Concrete Soundness

Authors:
Joseph Jaeger
Stefano Tessaro
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Abstract: This paper studies concrete security with respect to expected-time adversaries. Our first contribution is a set of generic tools to obtain tight bounds on the advantage of an adversary with expected-time guarantees. We apply these tools to derive bounds in the random-oracle and generic-group models, which we show to be tight. As our second contribution, we use these results to derive concrete bounds on the soundness of public-coin proofs and arguments of knowledge. Under the lens of concrete security, we revisit a paradigm by Bootle at al. (EUROCRYPT '16) that proposes a general Forking Lemma for multi-round protocols which implements a rewinding strategy with expected-time guarantees. We give a tighter analysis, as well as a modular statement. We adopt this to obtain the first quantitative bounds on the soundness of Bulletproofs (Bünz et al., S&P 2018), which we instantiate with our expected-time generic-group analysis to surface inherent dependence between the concrete security and the statement to be proved.
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BibTeX
@article{tcc-2020-30632,
  title={Expected-Time Cryptography: Generic Techniques and Applications to Concrete Soundness},
  booktitle={Theory of Cryptography},
  publisher={Springer},
  author={Joseph Jaeger and Stefano Tessaro},
  year=2020
}