230 research outputs found
Quantum Eavesdropping without Interception: An Attack Exploiting the Dead Time of Single Photon Detectors
The security of quantum key distribution (QKD) can easily be obscured if the
eavesdropper can utilize technical imperfections of the actual implementation.
Here we describe and experimentally demonstrate a very simple but highly
effective attack which even does not need to intercept the quantum channel at
all. Only by exploiting the dead time effect of single photon detectors the
eavesdropper is able to gain (asymptotically) full information about the
generated keys without being detected by state-of-the-art QKD protocols. In our
experiment, the eavesdropper inferred up to 98.8% of the key correctly, without
increasing the bit error rate between Alice and Bob significantly. Yet, we find
an evenly simple and effective countermeasure to inhibit this and similar
attacks
Quantum Advantage in Cryptography
Ever since its inception, cryptography has been caught in a vicious circle:
Cryptographers keep inventing methods to hide information, and cryptanalysts
break them, prompting cryptographers to invent even more sophisticated
encryption schemes, and so on. But could it be that quantum information
technology breaks this circle? At first sight, it looks as if it just lifts the
competition between cryptographers and cryptanalysts to the next level. Indeed,
quantum computers will render most of today's public key cryptosystems
insecure. Nonetheless, there are good reasons to believe that cryptographers
will ultimately prevail over cryptanalysts. Quantum cryptography allows us to
build communication schemes whose secrecy relies only on the laws of physics
and some minimum assumptions about the cryptographic hardware - leaving
basically no room for an attack. While we are not yet there, this article
provides an overview of the principles and state of the art of quantum
cryptography, as well as an assessment of current challenges and prospects for
overcoming them.Comment: 31 pages, 9 figures, 1 table. To appear in the AIAA journa
Quantum cryptography: key distribution and beyond
Uniquely among the sciences, quantum cryptography has driven both
foundational research as well as practical real-life applications. We review
the progress of quantum cryptography in the last decade, covering quantum key
distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK
Quantum Cryptography: Key Distribution and Beyond
Uniquely among the sciences, quantum cryptography has driven both foundational research asĀ well as practical real-life applications. We review the progress of quantum cryptography in the lastĀ decade, covering quantum key distribution and other applications.Quanta 2017; 6: 1ā47
Practical unconditionally secure signature schemes and related protocols
The security guarantees provided by digital signatures are vital to many modern applications such as online banking, software distribution, emails and many more. Their ubiquity across digital communications arguably makes digital signatures one of the most important inventions in cryptography. Worryingly, all commonly used schemes ā RSA, DSA and ECDSA ā provide only computational security, and are rendered completely insecure by quantum computers. Motivated by this threat, this thesis focuses on unconditionally secure signature (USS) schemes ā an information theoretically secure analogue of digital signatures. We present and analyse two new USS schemes. The ļ¬rst is a quantum USS scheme that is both information-theoretically secure and realisable with current technology. The scheme represents an improvement over all previous quantum USS schemes, which were always either realisable or had a full security proof, but not both. The second is an entirely classical USS scheme that uses minimal resources and is vastly more eļ¬cient than all previous schemes, to such an extent that it could potentially ļ¬nd real-world application. With the discovery of such an eļ¬cient classical USS scheme using only minimal resources, it is diļ¬cult to see what advantage quantum USS schemes may provide. Lastly, we remain in the information-theoretic security setting and consider two quantum protocols closely related to USS schemes ā oblivious transfer and quantum money. For oblivious transfer, we prove new lower bounds on the minimum achievable cheating probabilities in any 1-out-of-2 protocol. For quantum money, we present a scheme that is more eļ¬cient and error tolerant than all previous schemes. Additionally, we show that it can be implemented using a coherent source and lossy detectors, thereby allowing for the ļ¬rst experimental demonstration of quantum coin creation and veriļ¬cation
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