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Questions tagged [key-distribution]

For questions about quantum key distribution (QKD). It is a secure communication method which implements a cryptographic protocol involving components of quantum mechanics. (Wikipedia) In case it's also a question about quantum-cryptography, use the [cryptography] tag along with this.

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Do we consider the entangled-based protocol E91 to be a device-independent protocol?

Since both rely on Bell inequalities to maintain security, does the Ekert protocol rely on trustworthiness of the devices?
ibtissam's user avatar
1 vote
1 answer
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In e91 protocol, if one of the bases combination was not chosen, what should be done to avoid division by zero?

In e91 protocol, if one of the bases combination was not chosen, what should be done in this case to avoid division by zero? One solution that comes to mind is setting the whole value to zero, but is ...
Mohamed Elsheikh's user avatar
1 vote
0 answers
23 views

Why isn't quantum error correction used in quantum key distribution protocols like BB84?

In QKD protocols like BB84 there are some post-processing steps after obtaining the sifted key. One of them is error correction so that Alice and Bob end up with the same string of bits. This is to ...
Omeglac's user avatar
  • 155
0 votes
0 answers
13 views

What is the state of the art in Device-Independent QKD and Twin-Field QKD?

I understand that DIQKD would solve most problems related to QKD like side-channel attacks and with TFQKD we would also be able to avoid the use of quantum repeaters. So at least theoretically it ...
Omeglac's user avatar
  • 155
1 vote
2 answers
53 views

In a QKD protocol such as BB84 how do Alice and Bob deal with lost or undetected photons?

In a quantum key distribution protocol such as BB84 how do Alice and Bob deal with lost or undetected photons in practice? Imagine Alice sends 1001 using X Z X Z bases. Bob then receives 101 (second ...
Omeglac's user avatar
  • 155
3 votes
1 answer
52 views

Benefits of using quantum encrypted keys

Considering, in a perfect world everyone has the capability to create a quantum key. What would the benefits of using quantum encrypted keys instead of using classically encrypted keys? Besides the ...
Snarz's user avatar
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1 vote
1 answer
95 views

Entanglement-based attack on E91 protocol

My first question is if the bell pair that Alice and Bob share for the E91 protocol matters since I've seen different resources use different pairs for the explanation. My second question is say they ...
Omeglac's user avatar
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2 votes
1 answer
145 views

Doubt in understanding the use of Uhlmann's Theorem in BB84 security proof

I was going through the security proof of the BB84 protocol by Dr. Ramona Wolf. I am having trouble following the equation (used at 8:53) for the fidelity, \begin{align*} F(\rho_{ABE},\left|\phi\right\...
HypnoticZebra's user avatar
2 votes
0 answers
31 views

Role of eavesdroppers in B92 of phase modulation

I have a question about the phase modulation scheme described in Bennett et al. (1992). In figure 2 of this paper, it says Source at left supplies the coherent pulse of M>1 expected photons ...
tare_'s user avatar
  • 51
2 votes
1 answer
96 views

Choosing E91/BB84 basis states and angles

What is the logic for choosing the angles of E91 for the specific basis states? I have noticed a variety of different angles being used as the basis states for Alice and Bob. Would adding more basis ...
imung's user avatar
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1 vote
0 answers
25 views

Role of Intensity Modulator's Extinction Ratio on transmitter side in COW/DPS QKD using Weak Coherent Pulses

What is the role of having a high extinction ratio (30-40 dB) for the intensity modulator on the transmitter side in COW/DPS QKD using Weak Coherent Pulses, when ultimately the pulses have to be ...
A_Kumar's user avatar
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2 votes
2 answers
350 views

Why does entanglement of 3 qubits break this?

Another user asked about the Ekert Quantum Key Distribution protocol: Alice and Bob each randomly choose one of three bases separated by $120^{\circ} $ in which to measure, and then later compare the ...
Frank Yellin's user avatar
0 votes
1 answer
181 views

Which protocol does the Qiskit textbook use for Quantum Key Distribution?

I've worked through a couple different protocols for quantum key distribution, but when I look at the Qiskit textbook on this page I am unable to determine which one was used in this lesson. If anyone ...
PGibbon's user avatar
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1 answer
788 views

What type of attack(individual attack, collective attack, coherent attack) is a PNS attack?

While studying the attack method of QKD, I found that intercept and resend attack is an example of an individual attack. What are the examples of collective attack and coherent attack? Specifically, ...
James Thomas's user avatar
3 votes
2 answers
102 views

E91 probability of wrong conclusion of eavesdropper

If I use E91 protocol for QKD, with n bits exchanged, what is the probability that you think there is an eavesdropper but there really isn't one or the opposite you think there is no eavesdropper but ...
SlimeyGuy123's user avatar
2 votes
1 answer
435 views

In the E91 protocol, how can Alice and Bob detect Eve if she waits to measure until A&B publish their bases?

I'm studying the E91 protocol. Suppose Eve has a qubit entangled with Alice's and Bob's qubits. I understand how Alice and Bob can detect Eve if Eve measures before A&B by testing Bell's ...
Flipper's user avatar
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0 votes
1 answer
113 views

BB84 Protocol doubt

I was studying BB84 protocol from lecture notes by John Watrous. I had some doubts which i thought of asking. Here is the protocol. Alice prepares strings $x=(01110100)$ and $y=(11010001)$. based on ...
Upstart's user avatar
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2 votes
1 answer
406 views

Why is Measurement Device Independent (MDI) Quantum Key Distribution (QKD) truly MDI?

This is a repost from a question I posted in the physics stack exchange I am having a hard time understanding why MDI-QKD is truly measurement device independent. My current vision is that Charlie (...
Danilo Guimarães's user avatar
3 votes
1 answer
85 views

Doubt in CSS error correction step

At the end of page 3 in Simple proof of security of the BB84 QKD, the following equation (equation 4) is given : $$ \begin{array}{r} \frac{1}{2^{n}\left|C_{2}\right|} \sum_{z}\left[\sum_{w_{1}, w_{2} ...
IamKnull's user avatar
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3 votes
1 answer
226 views

Doubt in Simple proof of Security of the BB84 QKD

I am not able to understand an argument from Simple proof of Security of the BB84 QKD; I need your help. In page 2 it is mentioned that "Alice can measure her half of the encoded EPR pairs before ...
IamKnull's user avatar
  • 433
2 votes
1 answer
171 views

Major Security proofs available for Device-Independent QKD

I've lately started working on a DI-QKD project. I've started looking into Vazirani and Vidick's PRL paper on Device-Independent QKD security proof. It's proving to be quite time-consuming for me to ...
IamKnull's user avatar
  • 433
1 vote
1 answer
183 views

Can we do error correction for entangled particles?

There are several quantum error correction techniques, such as 3-qubit bit-flip code, and Shor’s 9-qubit code. 3-qubit bit-flip code is a straightforward technique for correcting a single error (...
m.aldarwbi's user avatar
2 votes
1 answer
188 views

Understanding the (2,3) threshold quantum secret sharing scheme in Cleve et al. 1999

In the paper "How to share quantum secret" by R.Cleve et al (arxiv). There is an example of secret sharing using qutrit in a (2,3) threshold scheme. $$\alpha\vert0\rangle+\beta\vert1\rangle+\...
Learning's user avatar
5 votes
0 answers
253 views

Average secret key rate calculation

I am working on a problem related to average secret key rate calculation in satellite quantum key distribution (QKD). The problem is similar to a paper on arXiv:1712.09722 (P. No. 21). In a single ...
Shikhar Arora's user avatar
2 votes
1 answer
2k views

Quantum bit error rate

I am trying to understand the quantum key distribution and Quantum Bit Error Rate (QBER). I have question: Why is the QBER given by the average of the diagonals of the crosstalk matrix? Why the need ...
user avatar
2 votes
1 answer
297 views

What is meant with "reconciliation" in CV QKD?

I am working on a paper about Continuous Variable QKD. (https://arxiv.org/abs/1711.08500v2) I read about direct and reverse reconciliation in this paper. I don't understand what exactly Reconciliation ...
Kianoosh.kargar's user avatar
2 votes
1 answer
149 views

The Methodology of Quantum Key Distributions Systems

While reading an answer in Cryptography.SE I saw this As for security, that's one possible way to perform Quantum Key Distribution, another real thing. However, most current QKD systems sold today do ...
kelalaka's user avatar
  • 709
3 votes
1 answer
161 views

How are Franson Interferometers used to prove security in Photonic QKD Experiments?

I am currently reading this paper about Quantum Key Distribution Protocols which use Franson Interferometers to secure against eavesdroppers. I am having trouble understanding how the interferometers ...
Dunbar Birnie's user avatar
2 votes
1 answer
112 views

What is the intuition behind the following entanglement distillation protocol for continuous variable systems?

The protocol is: We start with a supply of identically prepared bipartite non-Gaussian states. The overall protocol then amounts to an iteration of the following basic steps. The states will be mixed ...
Devjyoti Tripathy's user avatar
1 vote
0 answers
80 views

In the BICONF information reconciliation protocol for QKD: should I also run BINARY on the complementary bits subset?

The descriptions of the BICONF information reconciliation protocol in the literature appear to be inconsistent. All descriptions agree that in each iteration Alice and Bob should select a random ...
Bruno Rijsman's user avatar
1 vote
1 answer
160 views

BB84 and B92 protocols: what is maximum and minimum bits that Alice and Bob might agree on?

Say Alice wants to transmit a 10-bit key. For the BB84 protocol, if we assume that Alice and Bob use the same basis to encode and decode 6 qubits (and different ones for the other 4), then what ...
David's user avatar
  • 81
9 votes
1 answer
513 views

What authentication protocol to use for BB84 and other QKD protocols?

Just like other classical and quantum key distribution protocols, BB84 is vulnerable to "man"-in-the-middle attacks, where Eve pretends to be Bob to Alice, and Eve pretends to be Alice to ...
Bruno Rijsman's user avatar
6 votes
3 answers
237 views

In what ways can qubits be used for applications that do not require entanglement?

Many good questions on this site have explored how entanglement lies at the boundary between the quantum world and the classical. For example in computational speedups, or teleportation or superdense ...
Mark Spinelli's user avatar
3 votes
1 answer
137 views

Counting channel uses of the lossy bosonic channel or definition of channel uses

The PLOB-bound ("Fundamental Limits of Repeaterless Quantum Communications") gives an asymptotic upper bound on the secret-key rate per used lossy bosonic channel. However, I'm not sure how to count ...
user1677907's user avatar
7 votes
1 answer
269 views

What role do Hecke operators and ideal classes perform in “Quantum Money from Modular Forms?”

Cross-posted on MO The original ideas from the 70's/80's - that begat the [BB84] quantum key distribution - concerned quantum money that is unforgeable by virtue of the no-cloning theorem. A ...
Mark Spinelli's user avatar
2 votes
1 answer
697 views

What is the difference between quantum key distribution and quantum key exchange?

Both the words 'Quantum Key Distribution' and 'Quantum Key Exchange' are used in quantum cryptography in the problem of a secure key distribution for encryption/decryption between parties. There are ...
K Sarkar's user avatar
  • 171
1 vote
1 answer
158 views

Implementing BB84 protocol with easily-obtained consumer hardware

Following on from my question on educational quantum computing toys, I was wondering whether it is possible to implement the BB84 key distribution protocol with easily-obtained consumer hardware - ...
ahelwer's user avatar
  • 4,138
6 votes
1 answer
144 views

Lattice based cryptography vs BB84

Am I correct in thinking that post-quantum cryptography such as lattice-based solutions run on classical computers are resistant to quantum attacks (as opposed to RMS), whereas quantum key ...
Matthew Giles's user avatar
14 votes
2 answers
1k views

Why is the efficiency of Ekert 91 Protocol 25%?

In Cabello's paper Quantum key distribution without alternative measurements, the author said "the number of useful random bits shared by Alice and Bob by transmitted qubit, before checking for ...
Lynn's user avatar
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22 votes
3 answers
2k views

Advantage of quantum key distribution over post-quantum cryptography

Post-quantum cryptography like lattice-based cryptography is designed to be secure even if quantum computers are available. It resembles currently employed encryptions, but is based on problems which ...
M. Stern's user avatar
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