27,524 research outputs found
Information-Theoretically Secure Protocols and Security Under Composition
We investigate the question of whether security of protocols in the information-theoretic setting (where the adversary is computationally unbounded) implies the security of these protocols under concurrent composition. This question is motivated by the folklore that all known protocols that are secure in the information-theoretic setting are indeed secure under concurrent composition. We provide answers to this question for a number of different settings (i.e., considering perfect versus statistical security, and concurrent composition with adaptive versus fixed inputs). Our results enhance the understanding of what is necessary for obtaining security under composition, as well as providing tools (i.e., composition theorems) that can be used for proving the security of protocols under composition while considering only the standard stand-alone definitions of security
Classical Cryptographic Protocols in a Quantum World
Cryptographic protocols, such as protocols for secure function evaluation
(SFE), have played a crucial role in the development of modern cryptography.
The extensive theory of these protocols, however, deals almost exclusively with
classical attackers. If we accept that quantum information processing is the
most realistic model of physically feasible computation, then we must ask: what
classical protocols remain secure against quantum attackers?
Our main contribution is showing the existence of classical two-party
protocols for the secure evaluation of any polynomial-time function under
reasonable computational assumptions (for example, it suffices that the
learning with errors problem be hard for quantum polynomial time). Our result
shows that the basic two-party feasibility picture from classical cryptography
remains unchanged in a quantum world.Comment: Full version of an old paper in Crypto'11. Invited to IJQI. This is
authors' copy with different formattin
Quantum Cryptography Beyond Quantum Key Distribution
Quantum cryptography is the art and science of exploiting quantum mechanical
effects in order to perform cryptographic tasks. While the most well-known
example of this discipline is quantum key distribution (QKD), there exist many
other applications such as quantum money, randomness generation, secure two-
and multi-party computation and delegated quantum computation. Quantum
cryptography also studies the limitations and challenges resulting from quantum
adversaries---including the impossibility of quantum bit commitment, the
difficulty of quantum rewinding and the definition of quantum security models
for classical primitives. In this review article, aimed primarily at
cryptographers unfamiliar with the quantum world, we survey the area of
theoretical quantum cryptography, with an emphasis on the constructions and
limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference
Fundamental And Practical Problems of QKD Security - the Actual and the Perceived Situation
It is widely believed that quantum key distribution (QKD) has been proved
unconditionally secure for realistic models applicable to various current
experimental schemes. Here we summarize briefly why this is not the case, from
both the viewpoints of fundamental quantitative security and applicable models
of security analysis, with some morals drawn.Comment: This paper is being revised. It will appear later. 14 pages, 2
figure
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