49,686 research outputs found
Secure quantum channels with correlated twin laser beams
This work is the development and analysis of the recently proposed quantum
cryptographic protocol, based on the use of the two-mode coherently correlated
states. The protocol is supplied with the cryptographic control procedures. The
quantum noise influence on the channel error properties is examined. State
detection features are proposed
Anonymous credit cards and their collusion analysis
Communications networks are traditionally used to bring information together. They can also be used to keep information apart in order to protect personal privacy. A cryptographic protocol specifies a process by which some information is transferred among some users and hidden from others. We show how to implement anonymous credit cards using simple cryptographic protocols. We pose, and solve, a collusion problem which determines whether it is possible for a subset of users to discover information that is designed to be hidden from them during or after execution of the anonymous credit card protocol
Cryptographic security of quantum key distribution
This work is intended as an introduction to cryptographic security and a
motivation for the widely used Quantum Key Distribution (QKD) security
definition. We review the notion of security necessary for a protocol to be
usable in a larger cryptographic context, i.e., for it to remain secure when
composed with other secure protocols. We then derive the corresponding security
criterion for QKD. We provide several examples of QKD composed in sequence and
parallel with different cryptographic schemes to illustrate how the error of a
composed protocol is the sum of the errors of the individual protocols. We also
discuss the operational interpretations of the distance metric used to quantify
these errors.Comment: 31+23 pages. 28 figures. Comments and questions welcom
Using of small-scale quantum computers in cryptography with many-qubit entangled states
We propose a new cryptographic protocol. It is suggested to encode
information in ordinary binary form into many-qubit entangled states with the
help of a quantum computer. A state of qubits (realized, e.g., with photons) is
transmitted through a quantum channel to the addressee, who applies a quantum
computer tuned to realize the inverse unitary transformation decoding of the
message. Different ways of eavesdropping are considered, and an estimate of the
time needed for determining the secret unitary transformation is given. It is
shown that using even small quantum computers can serve as a basis for very
efficient cryptographic protocols. For a suggested cryptographic protocol, the
time scale on which communication can be considered secure is exponential in
the number of qubits in the entangled states and in the number of gates used to
construct the quantum network
Quantum cryptography based on Wheeler's delayed choice experiment
We describe a cryptographic protocol in which Wheeler's delayed choice
experiment is used to generate the key distribution. The protocol, which uses
photons polarized only along one axis, is secure against general attacks.Comment: 4 pages, LaTeX file, no figure
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