Questions tagged [cryptography]

For questions about cryptography as it relates directly to quantum computing. Not for general cryptographic methods.

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What are conceptual open problem in quantum communications and cryptography?

I recently heard that most of the challenges in quantum communications nowadays are related to "practical" engineering implementations and there are no longer "real" conceptual ...
19 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 (...
52 views

How would you apply quantum computing to break a symmetric key system?

How would you apply quantum computing to break a symmetric key system? Do you attack the plaintext password by bruteforcing? Or the mathematical process of the encryption algorithm?
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Show That an Intercept and Resend Attack on all qubits reduces mutual information

Exercise 5.3.3 With no eavesdropping the mutual information $H(A:B)$ between the substring of $\mathcal R$ held by Alice and $\mathcal R'$ held by Bob is $1$ bit. Show that if Eve is performing an ...
51 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 ...
116 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 ...
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What is the computational complexity limitation of classical client delegated quantum computing CCDQC protocols?

The number of T-gates in quantum search reaches $O(2^{m/2} \cdot\text{poly}(m))$, which is beyond the capability of CHE-based QHE schemes. But is it the same case for other bilnd QC protocols? and ...
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Is it possible to convert classical oracle to quantum ones?

If an attacker possesses a classical oracle, so she could apply chosen plain text attacks. Is there an easy way to reduce this oracle to quantum ones allowing her to make quantum chosen plain text ...
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Mahadev's classical homomorphic encryption for quantum circuits and NISQ computing

I'm currently reading Mahadev's paper Classical Homomorphic Encryption for Quantum Circuits: https://arxiv.org/abs/1708.02130 I was told that Mahadev's scheme is not something that can be implemented ...
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How to measure and get the result in a Graph state

According to this definition, suppose I have a graph on $3$ vertices, $v_1,v_2,v_3$, such that I have the Graph state vector $$|G\rangle= |0++\rangle+|1++\rangle$$ Suppose I have a secret say $S=1$,so ...
33 views

Does the bit generated password using QKD protocols need to be converted to another base? [closed]

I am currently implementing some QKD protocols using Qiskit and I came up with the following question: After the protocol is finished, a true random password is generated using 0s and 1s, however, and ...
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Paper references on how quantum algorithms have an impact on cryptography?

Could you please help me in finding some research paper references on the impact of Quantum algorithms on symmetric and asymmetric cryptography ? Also, I request if I can get some references or notes ...
155 views

How can one cheat in Mahadev's classical verification protocol if one can find a "claw''?

I was going through the seminal paper of Urmila Mahadev on Classical Verification of Quantum Computations(for an overview see this excellent talk by her). As a physicist by training, I am not very ...
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Show when $a_k$ and $b_k$ are correlated when measuring in different bases, in the BB84 protocol

I'm trying to answer the following question about the BB84 protocol from Nielsen and Chuang's Introduction to Quantum Information. As I understand it, the string $b$ is determining whether we are ...
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Can a qubit be entangled with an arbitrary quantum state, without altering it?

For example, if an adversary were to get hold of one half of an entangled 2-qubit quantum state, $|\psi \rangle$, travelling along a channel, would they be able to entangle one of their own qubits ...
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Shor vs Schnorr: A classical algorithm for breaking RSA? [duplicate]

I am not sure why I haven't heard much chatter about this paper by Dr. Claus Peter Schnorr where he claims to have come up with a classical algorithm to break the RSA protocol. The construction is ...
78 views

Is it possible to have access to a quantum computer to break a BitLocker key (maybe with Shor's algorithm) and have access to my data? Here what happened to me: after I've changed my LENOVO X270 ...
92 views

Sources for quantum cryptography and post quantum cryptography

I am a beginner in quantum computing, and I understand the basics of quantum computing. Can anyone suggest me a beginners material for quantum cryptography and post quantum cryptography? Book, Video ...
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How is it possible for Quantum computers to handle encryption if their states are unstable?

I've been doing research on quantum computers and encryption. How is it possible for quantum computers to solve complex encryption algorithms while their qubit states are not even predictable? How is ...
59 views

Where does the time complexity come from when applying Grover's algorithm to AES?

I have just finished multiple readings of Applying Grover’s algorithm to AES: quantum resource estimates, a 2015 paper by Markus Grassl, Brandon Langenberg, Martin Roetteler, and Rainer Steinwandt. ...
102 views

How are inputs during the quantum communication between Alice and Bob placed in the Galois Field?

I have to write a report on "Classical Interaction Cannot Replace a Quantum Message" by Gavinsky (arxiv link). The author gave a lecture, and at 14:55 explains that a communication problem ...
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Theoretical obstacles for a BZK-like quantum algorithm instantiated with a subroutine operates at small block size?

Obviously this specific topic had not been thoroughly studied, and the best we can do are empirical deductions based on past experience with quantum algorithms. The security of lattice-based public-...
103 views

Do quantum computers have any security risks associated with them? [closed]

I would, like to know for my company, as we are looking to start the process of moving towards quantum safeness.
66 views

(Why) does unconditionally secure multi-party quantum computation imply quantum bit commitment?

I have read in several papers now that information-theoretically secure multi-party quantum computation (MQPC) with a dishonest majority ($t \geq n/2$) is impossible because of the impossibility of ...
88 views

Non-ideal bit commitment and coin tossing

Can someone please explain rigorously the reasoning behing non-ideal ($\epsilon$-concealing and $\delta$-binding) bit commitment scheme and the impossibility of coin tossing. What is bias in coin ...
116 views

How exactly does Grovers algorithm "crack" symmetric key encryption?

How exactly does Grovers algorithm "crack" symmetric key encryption? I searched around on the internet, and found that it could make the key length effectively half as long, meaning you only ...
48 views

Any good resources for learning about quantum networks and how to do a simulation of BB84 protocol?

I'm a communication engineering student. And I'm thinking of doing my project on BB84 protocol but I don't know where to start. As a beginner, are there any documents or tutorials about quantum ...
186 views

Energy cost of quantum computation

A quantum computer can be modeled as a single unitary transition of a (large) effective quantum state to another. In order to get errors under control, quantum error correction is assumed. A logical ...
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Is there a notion of “computational security” in quantum cryptography?

In classical cryptography, security proofs are often based on the (assumed) computational hardness of some mathematical problem. Using the principles of quantum mechanics might provide means to design ...
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Is it a good idea to publish a research paper about the simulation of BB84 protocol?

I'm an engineering student. As my end of year project I've simulated BB84 protocol using simulaqron(python). I'm thinking about publishing a paper about this simulation. I haven't published any ...
96 views

Hadamard gate with two inputs in the circuit for the BB84 protocol?

I am reading the book "Quantum Computing verstehen" by Matthias Homeister. At the moment i'm having a look at the BB84 protocol (which is described in kind of an abstract way). In this chapter a ...
112 views

What are the thermodynamic limits of Shor's algorithm

The asymptotic time complexity of Grover's algorithm is the square root of the time of a brute force algorithm. However, according to Perlner and Liu, the thermodynamic behavior (theoretical minimum ...
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Is the BB84 protocol an example of "quantum supremacy"?

This is a fairly broad question, I hope it fits here. I am wondering if the BB84 protocol is an example of "quantum supremacy", ie. something a quantum computer can do but something that is assumed a ...
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Do we already know some problems, that would be hard to solve for quantum computers, and use them in cryptography? [duplicate]

I was wondering, whether there are any problems that we already know are difficult to solve for a quantum computer, and that we could potentially use in cryptography, just as we do now with e.g. the ...
134 views

Is Quantum Computing a problem for Cryptography?

How can we use Quantum Computing to break a Cryptosystem like RSA or AES-256? Can we use Quantum Computing to solve difficult mathematical problems like Discrete Logarithms or Prime Number ...
103 views

In the BB84 protocol, for what error thresholds can Alice and Bob not establish secure bits?

Suppose Alice and Bob can communicate over a quantum channel. The quantum channel is noiseless in the absence of eavesdropping, a condition that cannot be guaranteed. They can also communicate over a ...
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Why Alice and Bob don't get the same result when they measure in the same basis?

I'm simulating the BB84 protocol using simulaqron. My problem is that when Alice and Bob measure in the same basis, they don't get the same result. How can I fix this error? . BB84.py ...
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How to deal with noise in BB84 protocol?

BB84 protocol works followingly: Alice generate $N$ random qubits $a_i$ in state either $|0\rangle$ or $|1\rangle$ . These will be a key. Then she prepares $N$ random bits $b_{i}$. If $b_i=0$, an ...
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Like blockchains, other than the few quantum algorithms available out there, are quantum computers/algorithms a solution looking for a problem? [closed]

Like Distributed Ledger Technologies (DLT) and Blockchain, other than the few quantum algorithms available out there, are quantum computers/algorithms a solution looking for a problem? For one, I am ...
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How does a rectilinear filter used for QKD-BB84 detect both horizontal and vertical polarizations?

When using the BB84 algorithm for QKD, you arbitrarily choose which of two filters (bases) to use when detecting a photon: rectilinear or diagonal. If you choose rectilinear, you can detect ...
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What is the quantum state transmitted to Bob in BB84 protocol?

Sender (Alice) wants to exchange private encryption key with Bob using BB84 protocol. She generate a binary string (1010100010010111),and encode using Hadamard gate and identity gate (HHHIIHIHHIIIHIIH)...
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Show that if $b'$ and $b$ are uncorrelated, then $a'$ and $a$ are uncorrelated

Let $a'_k$ be Bob's measurement result of qubit ${\Psi_{a_kb_k}}$, assuming a noiseless channel with no eavesdropping. Show that when $b'_k\neq b_k$, $a'_k$ is random and completely uncorrelated ...
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Easiest hash function to implement on Qiskit

Trying to build an Oracle circuit for Grover's algorithm that will try to find a desired input in order to get a certain output of a hash function. Was wondering if there were any 4 or 8 bit hash ...
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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 ...
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Could quantum computers be useful for sending encrypted information over a classical channel?

A quantum computer running Shor's algorithm would be famously useful for decrypting information encrypted by many classical public-key cryptography algorithms. Is there any reason (either a specific ...
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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 ...
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What is the difference between intercept-resend attack and measure-resend attack?

I am going through different types of attacks that eve can perform on the quantum channel. I came across the intercept-resend attack and measure-resend attack. What is the difference between the two? ...
I have a secret say $s$. I have a dealer $D$ and three participants $A, B, C$. I want to share this secret $s$ in such a way that the participation of all $3$ is essential to reconstruct the secret. ...