Theory of Cryptography Conference

TCC 2009: Theory of Cryptography pp 350-367

Composing Quantum Protocols in a Classical Environment

  • Serge Fehr
  • Christian Schaffner
Conference paper

DOI: 10.1007/978-3-642-00457-5_21

Volume 5444 of the book series Lecture Notes in Computer Science (LNCS)
Cite this paper as:
Fehr S., Schaffner C. (2009) Composing Quantum Protocols in a Classical Environment. In: Reingold O. (eds) Theory of Cryptography. TCC 2009. Lecture Notes in Computer Science, vol 5444. Springer, Berlin, Heidelberg


We propose a general security definition for cryptographic quantum protocols that implement classical non-reactive two-party tasks. The definition is expressed in terms of simple quantum- information-theoretic conditions which must be satisfied by the protocol to be secure. The conditions are uniquely determined by the ideal functionality \(\mathcal{F}\) defining the cryptographic task to be implemented. We then show the following composition result. If quantum protocols π1,...,π securely implement ideal functionalities \(\mathcal{F}_1,\ldots,\mathcal{F}_\ell\) according to our security definition, then any purely classical two-party protocol, which makes sequential calls to \(\mathcal{F}_1,\ldots,\mathcal{F}_\ell\), is equally secure as the protocol obtained by replacing the calls to \(\mathcal{F}_1,\ldots,\mathcal{F}_\ell\) with the respective quantum protocols π1,...,π. Hence, our approach yields the minimal security requirements which are strong enough for the typical use of quantum protocols as subroutines within larger classical schemes. Finally, we show that recently proposed quantum protocols for secure identification and oblivious transfer in the bounded-quantum-storage model satisfy our security definition, and thus compose in the above sense.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Serge Fehr
    • 1
  • Christian Schaffner
    • 1
  1. 1.Centrum Wiskunde & Informatica (CWI)AmsterdamThe Netherlands