Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0006086 · Physical Review A

Secure key distribution via pre- and postselected quantum states

Jeffrey Bub

Published Feb 14, 2001• 20 citations
arXivHTMLPDF

Abstract

A quantum key distribution scheme whose security depends on the features of pre- and post-selected quantum states is described.
DOI
10.1103/physreva.63.032309

Related papers

Security of continuous-variable quantum cryptography with Gaussian postselection

Nathan Walk, Timothy C. Ralph, Thomas Symul +1 more

We extend the security analysis of continuous variable quantum-key-distribution protocols using a family of post selection schemes to account for arbitrary eavesdropping attacks. We show that the postselection protocol is equivalent to a virtual entanglement-based protocol including a distillation stage. We introduce a particular `Gaussian' post selection and demonstrate that the security can be calculated using only experimentally accessible quantities. Finally, we explicitly evaluate the performance for the case of a noisy Gaussian channel in the limit of unbounded key length and find improvements over all pre-existing continuous variable protocols in realistic regimes.

arXiv:1206.0936•Physical Review A•Feb 21, 2013•80 citations

A secure quantum key distribution scheme based on variable quantum encoding algorithms

Zhiwen Zhao, Yi Luo, Zhangji Zhao +1 more

Chinese Optics Letters•Jan 1, 2011•0 citations

Security analysis of quantum key distribution protocols

Florian Kanitschar

Quantum Key Distribution, or short QKD, aims to establish a secure key withoutmaking any additional assumptions about the abilities or computational power of an adversary who is only limited by the laws of nature. The process of finding a mathematical expression for, or at least a lower bound on, the secure keyrate of some QKD protocol, given relevant system parameters, is called securityproof. In this thesis, we use a recent numerical security proof technique to examine different post selection strategies for continuous-variable quantum key distribution(CV-QKD) protocols with quadrature phase-shift keying modulation and four or eight signal states. CV-QKD protocols use coherent states to encode information and measure the field-quadrature components by homodyne or heterodyne detection. The basic idea of the used numerical security proof technique is to solve thekey rate finding problem in a two-step process. In the first step, the problem is solved approximately, using a numerical algorithm, which yields an upper bound on the secure key rate. This is followed by step two, where the obtained upperbound is converted into a lower bound, using a sequence of theorems and taking numerical errors into account. Postselection aims to increase the secure key rate by removing those parts of the key, where a potential adversary might have gained more information than the communicating parties. The investigations are carried out both for the untrusted ideal and the trusted non-ideal detector scenario and we provide novel analytical results for the operators related to the postselection map.For four-state protocols, we demonstrate that a new cross-shaped postselectionstrategy out performs the state-of-the-art radial postselection scheme clearly in regions of medium to high transmission distances and medium to high values of noise and performs comparable to a more complicated radial&angular scheme. As the error-correction phase is a known bottleneck for many real QKD systems, we examined the secure key rate when a large fraction of the raw key is removed by postselection. We observe that a smart choice of the postselection strategy can increase the key rate while lowering the raw key rate, hence the computational effort in the error-correction phase. One can think this even further: For cross-shaped postselection we showed that the secure key rate is roughly 80% of the secure keyrate without postselection when only 20% of the raw key passes the postselection.For high noise levels this can be increased even further. The cross-shaped post-selection strategy can easily be implemented in the data processing of both new and existing CV-QKD systems, hence can increase the achievable secure key rate significantly. Furthermore, we examined the radial&angular postselection strategy which combines the advantages of the radial postselection scheme for low transmission distances and those of the cross-shaped postselection scheme for medium and high transmission distances on the cost of higher complexity.Additionally, we examine an eight-state phase-shift keying protocol and compare the obtained key rates to the key rates for the four-state protocol and investigate a radial postselection scheme. We observe that the 8PSK protocol yields higher secure key rates and reaches higher maximal achievable transmission distances than a QPSK protocol with a comparable postselection strategy, in particular for medium to high values of excess noise. Furthermore, we explore the relation between the achievable secure key rate and the probability to pass the postselectionphase for various noise-levels and two different practically relevant reconciliation efficiencies. This leads to similar strategies as found for the QPSK protocols to reduce the raw key rate significantly while decreasing the secure key rate only moderately. For very high values of excess noise, the raw key rate can be increased further compared to the key rate achieved without performing postselection whileremoving a large fraction of the raw key rate.

•Sep 1, 2021•0 citations

A secure authenticated semi-quantum key distribution scheme for semi-quantum environments

Chi‐Tung Chen, Cheng‐Chi Lee

Quantum Information Processing•Dec 18, 2024•6 citations

Enhancing Quantum-Safe Cryptography in TLS: The Role of Pre-Shared Keys

Tobias Frauenschläger, Lukas Füreder, Jürgen Mottok

Due to the increasing attainability of quantum computers, the threat to traditional cryptographic algorithms is more relevant than ever before. However, the field of Post-Quantum Cryptography (PQC) to address this is still young and may potentially exhibit security vulnerabilities. In this paper, the role of Pre-Shared Keys (PSK) is analyzed in an attack scenario with both traditional and post-quantum algorithms potentially broken. We present a scheme for improved integration of external PSKs into a PQC-secured TLS 1.3 handshake, with a focus on no security compromises and broad deployment options. In that context, the protection of long-term secrets on dedicated security tokens and the integration of Quantum Key Distribution (QKD) are elaborated. For QKD integration, our scheme enables a deployment without QKD-specific changes to TLS. In addition to the scheme itself, a reference implementation is presented and evaluated to demonstrate its technical viability. Our results indicate that the general integration of PSKs into the TLS handshake adds negligible overhead while substantially increasing the achieved security level. Although deployments using dedicated security tokens or QKD systems have a significant influence on handshake times, specific applications could benefit greatly from the added security guarantees.

International Conference on Applied Electronics•Sep 8, 2025•1 citation

A hybrid security model for quantum cryptography allowing to design practical schemes for long-distance key distribution with everlasting security

Romain Alléaume

•Oct 1, 2015•0 citations
We extend the security analysis of continuous variable quantum-key-distribution protocols using a family of post selection schemes to account for arbitrary eavesdropping attacks. We show that the postselection protocol is equivalent to a virtual entanglement-based protocol including a distillation stage. We introduce a particular `Gaussian' post selection and demonstrate that the security can be calculated using only experimentally accessible quantities. Finally, we explicitly evaluate the performance for the case of a noisy Gaussian channel in the limit of unbounded key length and find improvements over all pre-existing continuous variable protocols in realistic regimes.
Quantum Key Distribution, or short QKD, aims to establish a secure key withoutmaking any additional assumptions about the abilities or computational power of an adversary who is only limited by the laws of nature. The process of finding a mathematical expression for, or at least a lower bound on, the secure keyrate of some QKD protocol, given relevant system parameters, is called securityproof. In this thesis, we use a recent numerical security proof technique to examine different post selection strategies for continuous-variable quantum key distribution(CV-QKD) protocols with quadrature phase-shift keying modulation and four or eight signal states. CV-QKD protocols use coherent states to encode information and measure the field-quadrature components by homodyne or heterodyne detection. The basic idea of the used numerical security proof technique is to solve thekey rate finding problem in a two-step process. In the first step, the problem is solved approximately, using a numerical algorithm, which yields an upper bound on the secure key rate. This is followed by step two, where the obtained upperbound is converted into a lower bound, using a sequence of theorems and taking numerical errors into account. Postselection aims to increase the secure key rate by removing those parts of the key, where a potential adversary might have gained more information than the communicating parties. The investigations are carried out both for the untrusted ideal and the trusted non-ideal detector scenario and we provide novel analytical results for the operators related to the postselection map.For four-state protocols, we demonstrate that a new cross-shaped postselectionstrategy out performs the state-of-the-art radial postselection scheme clearly in regions of medium to high transmission distances and medium to high values of noise and performs comparable to a more complicated radial&angular scheme. As the error-correction phase is a known bottleneck for many real QKD systems, we examined the secure key rate when a large fraction of the raw key is removed by postselection. We observe that a smart choice of the postselection strategy can increase the key rate while lowering the raw key rate, hence the computational effort in the error-correction phase. One can think this even further: For cross-shaped postselection we showed that the secure key rate is roughly 80% of the secure keyrate without postselection when only 20% of the raw key passes the postselection.For high noise levels this can be increased even further. The cross-shaped post-selection strategy can easily be implemented in the data processing of both new and existing CV-QKD systems, hence can increase the achievable secure key rate significantly. Furthermore, we examined the radial&angular postselection strategy which combines the advantages of the radial postselection scheme for low transmission distances and those of the cross-shaped postselection scheme for medium and high transmission distances on the cost of higher complexity.Additionally, we examine an eight-state phase-shift keying protocol and compare the obtained key rates to the key rates for the four-state protocol and investigate a radial postselection scheme. We observe that the 8PSK protocol yields higher secure key rates and reaches higher maximal achievable transmission distances than a QPSK protocol with a comparable postselection strategy, in particular for medium to high values of excess noise. Furthermore, we explore the relation between the achievable secure key rate and the probability to pass the postselectionphase for various noise-levels and two different practically relevant reconciliation efficiencies. This leads to similar strategies as found for the QPSK protocols to reduce the raw key rate significantly while decreasing the secure key rate only moderately. For very high values of excess noise, the raw key rate can be increased further compared to the key rate achieved without performing postselection whileremoving a large fraction of the raw key rate.
Due to the increasing attainability of quantum computers, the threat to traditional cryptographic algorithms is more relevant than ever before. However, the field of Post-Quantum Cryptography (PQC) to address this is still young and may potentially exhibit security vulnerabilities. In this paper, the role of Pre-Shared Keys (PSK) is analyzed in an attack scenario with both traditional and post-quantum algorithms potentially broken. We present a scheme for improved integration of external PSKs into a PQC-secured TLS 1.3 handshake, with a focus on no security compromises and broad deployment options. In that context, the protection of long-term secrets on dedicated security tokens and the integration of Quantum Key Distribution (QKD) are elaborated. For QKD integration, our scheme enables a deployment without QKD-specific changes to TLS. In addition to the scheme itself, a reference implementation is presented and evaluated to demonstrate its technical viability. Our results indicate that the general integration of PSKs into the TLS handshake adds negligible overhead while substantially increasing the achieved security level. Although deployments using dedicated security tokens or QKD systems have a significant influence on handshake times, specific applications could benefit greatly from the added security guarantees.