345 research outputs found
Semi-quantum communication: Protocols for key agreement, controlled secure direct communication and dialogue
Semi-quantum protocols that allow some of the users to remain classical are
proposed for a large class of problems associated with secure communication and
secure multiparty computation. Specifically, first time semi-quantum protocols
are proposed for key agreement, controlled deterministic secure communication
and dialogue, and it is shown that the semi-quantum protocols for controlled
deterministic secure communication and dialogue can be reduced to semi-quantum
protocols for e-commerce and private comparison (socialist millionaire
problem), respectively. Complementing with the earlier proposed semi-quantum
schemes for key distribution, secret sharing and deterministic secure
communication, set of schemes proposed here and subsequent discussions have
established that almost every secure communication and computation tasks that
can be performed using fully quantum protocols can also be performed in
semi-quantum manner. Further, it addresses a fundamental question in context of
a large number problems- how much quantumness is (how many quantum parties are)
required to perform a specific secure communication task? Some of the proposed
schemes are completely orthogonal-state-based, and thus, fundamentally
different from the existing semi-quantum schemes that are
conjugate-coding-based. Security, efficiency and applicability of the proposed
schemes have been discussed with appropriate importance.Comment: 19 pages 1 figur
Symbolic Abstractions for Quantum Protocol Verification
Quantum protocols such as the BB84 Quantum Key Distribution protocol exchange
qubits to achieve information-theoretic security guarantees. Many variants
thereof were proposed, some of them being already deployed. Existing security
proofs in that field are mostly tedious, error-prone pen-and-paper proofs of
the core protocol only that rarely account for other crucial components such as
authentication. This calls for formal and automated verification techniques
that exhaustively explore all possible intruder behaviors and that scale well.
The symbolic approach offers rigorous, mathematical frameworks and automated
tools to analyze security protocols. Based on well-designed abstractions, it
has allowed for large-scale formal analyses of real-life protocols such as TLS
1.3 and mobile telephony protocols. Hence a natural question is: Can we use
this successful line of work to analyze quantum protocols? This paper proposes
a first positive answer and motivates further research on this unexplored path
Orthogonal-state-based protocols of quantum key agreement
Two orthogonal-state-based protocols of quantum key agreement (QKA) are
proposed. The first protocol of QKA proposed here is designed for two-party
QKA, whereas the second protocol is designed for multi-party QKA. Security of
these orthogonal-state-based protocols arise from monogamy of entanglement.
This is in contrast to the existing protocols of QKA where security arises from
the use of non-orthogonal state (non-commutativity principle). Further, it is
shown that all the quantum systems that are useful for implementation of
quantum dialogue and most of the protocols of secure direct quantum
communication can be modified to implement protocols of QKA.Comment: 9 pages, no figur
Orthogonal-state-based cryptography in quantum mechanics and local post-quantum theories
We introduce the concept of cryptographic reduction, in analogy with a
similar concept in computational complexity theory. In this framework, class
of crypto-protocols reduces to protocol class in a scenario , if for
every instance of , there is an instance of and a secure
transformation that reproduces given , such that the security of
guarantees the security of . Here we employ this reductive framework to
study the relationship between security in quantum key distribution (QKD) and
quantum secure direct communication (QSDC). We show that replacing the
streaming of independent qubits in a QKD scheme by block encoding and
transmission (permuting the order of particles block by block) of qubits, we
can construct a QSDC scheme. This forms the basis for the \textit{block
reduction} from a QSDC class of protocols to a QKD class of protocols, whereby
if the latter is secure, then so is the former. Conversely, given a secure QSDC
protocol, we can of course construct a secure QKD scheme by transmitting a
random key as the direct message. Then the QKD class of protocols is secure,
assuming the security of the QSDC class which it is built from. We refer to
this method of deduction of security for this class of QKD protocols, as
\textit{key reduction}. Finally, we propose an orthogonal-state-based
deterministic key distribution (KD) protocol which is secure in some local
post-quantum theories. Its security arises neither from geographic splitting of
a code state nor from Heisenberg uncertainty, but from post-measurement
disturbance.Comment: 12 pages, no figure, this is a modified version of a talk delivered
by Anirban Pathak at Quantum 2014, INRIM, Turin, Italy. This version is
published in Int. J. Quantum. Info
Asymmetric Quantum Dialogue in Noisy Environment
A notion of asymmetric quantum dialogue (AQD) is introduced. Conventional
protocols of quantum dialogue are essentially symmetric as both the users
(Alice and Bob) can encode the same amount of classical information. In
contrast, the scheme for AQD introduced here provides different amount of
communication powers to Alice and Bob. The proposed scheme, offers an
architecture, where the entangled state and the encoding scheme to be shared
between Alice and Bob depends on the amount of classical information they want
to exchange with each other. The general structure for the AQD scheme has been
obtained using a group theoretic structure of the operators introduced in
(Shukla et al., Phys. Lett. A, 377 (2013) 518). The effect of different types
of noises (e.g., amplitude damping and phase damping noise) on the proposed
scheme is investigated, and it is shown that the proposed AQD is robust and
uses optimized amount of quantum resources.Comment: 11 pages, 2 figure
A novel two-party semiquantum key distribution protocol based on GHZ-like states
In this paper, we propose a novel two-party semiquantum key distribution
(SQKD) protocol by only employing one kind of GHZ-like state. The proposed SQKD
protocol can create a private key shared between one quantum party with
unlimited quantum abilities and one classical party with limited quantum
abilities without the existence of a third party. The proposed SQKD protocol
doesn't need the Hadamard gate or quantum entanglement swapping. Detailed
security analysis turns out that the proposed SQKD protocol can resist various
famous attacks from an outside eavesdropper, such as the Trojan horse attacks,
the entangle-measure attack, the double CNOT attacks, the measure-resend attack
and the intercept-resend attack.Comment: 15 pages, 2 figures, 1 tabl
A Simplified Hierarchical Dynamic Quantum Secret Sharing Protocol with Added Features
Generalizing the notion of dynamic quantum secret sharing (DQSS), a
simplified protocol for hierarchical dynamic quantum secret sharing (HDQSS) is
proposed and it is shown that the protocol can be implemented using any
existing protocol of quantum key distribution, quantum key agreement or secure
direct quantum communication. The security of this proposed protocol against
eavesdropping and collusion attacks is discussed with specific attention
towards the issues related to the composability of the subprotocols that
constitute the proposed protocol. The security and qubit efficiency of the
proposed protocol is also compared with that of other existing protocols of
DQSS. Further, it is shown that it is possible to design a semi-quantum
protocol of HDQSS and in principle, the protocols of HDQSS can be implemented
using any quantum state. It is also noted that the completely
orthogonal-state-based realization of HDQSS protocol is possible and that HDQSS
can be experimentally realized using a large number of alternative approaches.Comment: 9 pages, 1 figur
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
Incremental Composition in Distributional Semantics
Despite the incremental nature of Dynamic Syntax (DS), the semantic grounding of it remains that of predicate logic, itself grounded in set theory, so is poorly suited to expressing the rampantly context-relative nature of word meaning, and related phenomena such as incremental judgements of similarity needed for the modelling of disambiguation. Here, we show how DS can be assigned a compositional distributional semantics which enables such judgements and makes it possible to incrementally disambiguate language constructs using vector space semantics. Building on a proposal in our previous work, we implement and evaluate our model on real data, showing that it outperforms a commonly used additive baseline. In conclusion, we argue that these results set the ground for an account of the non-determinism of lexical content, in which the nature of word meaning is its dependence on surrounding context for its construal
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