5 research outputs found
Unconditional security from noisy quantum storage
We consider the implementation of two-party cryptographic primitives based on
the sole assumption that no large-scale reliable quantum storage is available
to the cheating party. We construct novel protocols for oblivious transfer and
bit commitment, and prove that realistic noise levels provide security even
against the most general attack. Such unconditional results were previously
only known in the so-called bounded-storage model which is a special case of
our setting. Our protocols can be implemented with present-day hardware used
for quantum key distribution. In particular, no quantum storage is required for
the honest parties.Comment: 25 pages (IEEE two column), 13 figures, v4: published version (to
appear in IEEE Transactions on Information Theory), including bit wise
min-entropy sampling. however, for experimental purposes block sampling can
be much more convenient, please see v3 arxiv version if needed. See
arXiv:0911.2302 for a companion paper addressing aspects of a practical
implementation using block samplin
Bit Commitment from Non-Signaling Correlations
Central cryptographic functionalities such as encryption, authentication, or
secure two-party computation cannot be realized in an information-theoretically
secure way from scratch. This serves as a motivation to study what (possibly
weak) primitives they can be based on. We consider as such starting points
general two-party input-output systems that do not allow for message
transmission, and show that they can be used for realizing unconditionally
secure bit commitment as soon as they are non-trivial, i.e., cannot be securely
realized from distributed randomness only.Comment: New title. Changes in the introduction and the preliminarie
On the Efficiency of Classical and Quantum Oblivious Transfer Reductions
Due to its universality oblivious transfer (OT) is a primitive of great importance in secure multi-party computation.
OT is impossible to implement from scratch in an unconditionally secure way, but there are many reductions of OT to other variants of OT, as well as other primitives such as noisy channels. It is important to know how efficient such unconditionally secure reductions can be in principle, i.e., how many instances of a given primitive are at least needed to implement OT. For perfect (error-free) implementations good lower bounds are known, e.g. the bounds by Beaver (STOC \u2796) or by Dodis and Micali (EUROCRYPT \u2799). However, in practice one is usually willing to tolerate a small probability of error and it is known that these statistical reductions can in general be much more efficient. Thus, the known bounds have only limited application. In the first part of this work we provide bounds on the efficiency of secure (one-sided) two-party computation of arbitrary finite functions from distributed randomness in the statistical case. From these results we derive bounds on the efficiency of protocols that use (different variants of) OT as a black-box. When applied to implementations of OT, our bounds generalize known results to the statistical case. Our results hold in particular for transformations between a finite number of primitives and for any error. Furthermore, we provide bounds on the efficiency of protocols implementing Rabin OT.
In the second part we study the efficiency of quantum protocols implementing OT. Recently, Salvail, Schaffner and Sotakova (ASIACRYPT \u2709) showed that most classical lower bounds for perfectly secure reductions of OT to distributed randomness still hold in a quantum setting. We present a statistically secure protocol that violates these bounds by an arbitrarily large factor. We then present a weaker lower bound that does hold in the statistical quantum setting. We use this bound to show that even quantum protocols cannot extend OT. Finally, we present two lower bounds for reductions of OT to commitments and a protocol based on string commitments that is optimal with respect to both of these bounds