4,222 research outputs found
Robust Cryptography in the Noisy-Quantum-Storage Model
It was shown in [WST08] that cryptographic primitives can be implemented
based on the assumption that quantum storage of qubits is noisy. In this work
we analyze a protocol for the universal task of oblivious transfer that can be
implemented using quantum-key-distribution (QKD) hardware in the practical
setting where honest participants are unable to perform noise-free operations.
We derive trade-offs between the amount of storage noise, the amount of noise
in the operations performed by the honest participants and the security of
oblivious transfer which are greatly improved compared to the results in
[WST08]. As an example, we show that for the case of depolarizing noise in
storage we can obtain secure oblivious transfer as long as the quantum
bit-error rate of the channel does not exceed 11% and the noise on the channel
is strictly less than the quantum storage noise. This is optimal for the
protocol considered. Finally, we show that our analysis easily carries over to
quantum protocols for secure identification.Comment: 34 pages, 2 figures. v2: clarified novelty of results, improved
security analysis using fidelity-based smooth min-entropy, v3: typos and
additivity proof in appendix correcte
Generation and Distribution of Quantum Oblivious Keys for Secure Multiparty Computation
The oblivious transfer primitive is sufficient to implement secure multiparty
computation. However, secure multiparty computation based only on classical
cryptography is severely limited by the security and efficiency of the
oblivious transfer implementation. We present a method to efficiently and
securely generate and distribute oblivious keys by exchanging qubits and by
performing commitments using classical hash functions. With the presented
hybrid approach, quantum and classical, we obtain a practical and high-speed
oblivious transfer protocol, secure even against quantum computer attacks. The
oblivious distributed keys allow implementing a fast and secure oblivious
transfer protocol, which can pave the way for the widespread of applications
based on secure multiparty computation.Comment: 11 pages, 5 figure
Practical and unconditionally secure spacetime-constrained oblivious transfer
Spacetime-constrained oblivious transfer (SCOT) extends the fundamental
primitive of oblivious transfer to Minkowski space. SCOT and location oblivious
data transfer (LODT) are the only known cryptographic tasks with classical
inputs and outputs for which unconditional security needs both quantum theory
and relativity. We give an unconditionally secure SCOT protocol that,
contrasting previous SCOT and LODT protocols, is practical to implement with
current technology, where distant agents need only communicate classical
information, while quantum communication occurs at a single location. We also
show that our SCOT protocol can be used to implement unconditionally secure
quantum relativistic bit commitment.Comment: Accepted manuscrip
Cryptography in the Bounded-Quantum-Storage Model
This thesis initiates the study of cryptographic protocols in the
bounded-quantum-storage model. On the practical side, simple protocols for
Rabin Oblivious Transfer, 1-2 Oblivious Transfer and Bit Commitment are
presented. No quantum memory is required for honest players, whereas the
protocols can only be broken by an adversary controlling a large amount of
quantum memory. The protocols are efficient, non-interactive and can be
implemented with today's technology.
On the theoretical side, new entropic uncertainty relations involving
min-entropy are established and used to prove the security of protocols
according to new strong security definitions. For instance, in the realistic
setting of Quantum Key Distribution (QKD) against quantum-memory-bounded
eavesdroppers, the uncertainty relation allows to prove the security of QKD
protocols while tolerating considerably higher error rates compared to the
standard model with unbounded adversaries.Comment: PhD Thesis, BRICS, University of Aarhus, Denmark, 128 page
Implementation of two-party protocols in the noisy-storage model
The noisy-storage model allows the implementation of secure two-party
protocols under the sole assumption that no large-scale reliable quantum
storage is available to the cheating party. No quantum storage is thereby
required for the honest parties. Examples of such protocols include bit
commitment, oblivious transfer and secure identification. Here, we provide a
guideline for the practical implementation of such protocols. In particular, we
analyze security in a practical setting where the honest parties themselves are
unable to perform perfect operations and need to deal with practical problems
such as errors during transmission and detector inefficiencies. We provide
explicit security parameters for two different experimental setups using weak
coherent, and parametric down conversion sources. In addition, we analyze a
modification of the protocols based on decoy states.Comment: 41 pages, 33 figures, this is a companion paper to arXiv:0906.1030
considering practical aspects, v2: published version, title changed in
accordance with PRA guideline
Device-Independent Oblivious Transfer from the Bounded-Quantum-Storage-Model and Computational Assumptions
We present a device-independent protocol for oblivious transfer (DIOT) in the
bounded-quantum-storage-model, and analyze its security. Our protocol is
everlastingly secure and aims to be more practical than previous DIOT
protocols, since it does not require non-communication assumptions that are
typical from protocols that use Bell inequality violations; instead, the
device-independence comes from a recent self-testing protocol which makes use
of a post-quantum computational assumption.Comment: 24 page
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
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