Questions tagged [quantum-cryptography]

Quantum cryptography describes the use of quantum mechanical effects to perform cryptographic tasks. This is not to be confused with quantum computing or cryptanalysis techniques such as Shor's algorithm.

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implications of shor's algorithm on $F_{2^m}$ elliptic curves and GHASH

The security of elliptic curves depends on the difficulty of the discrete logarithm problem. Should Shor's Algorithm ever prove viable then elliptic curves would cease to offer any useful security ...
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What kind of operators should I perform on 4-qubit state $|\psi\rangle_A|GHZ\rangle$ to get expression like $|\Psi\rangle_4$?

I'm reading the paper "Quantum secret sharing" by Hillery, Bužek and Berthiaume (Phys. Rev. A, 1999; preprint on arXiv) and I have a question about it. Let's say Alice wants to send Bob qubit in ...
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Is quantum key distribution safe against MITM attacks too?

i read this recently: http://www.newscientist.com/article/dn12786-quantum-cryptography-to-protect-swiss-election.html and some parts of this: http://en.wikipedia.org/wiki/Quantum_key_distribution ...
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Using XL Algorithm to solve overdetermined systems, simple example required

Can someone give an example of how the XL algorithm is used to solve an overdetermined system as apposed to just a general case? I have a fairly good understanding of how steps of the algorithm work, ...
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What happens if the first input block is identical to the key in DES?

In Data Encryption Standard (DES), M is the input message and K is the key of 64 bits size. M is divided into n 64 sized blocks (B1,B2,B3...Bn).
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Why is it difficult to encrypt large amounts of information using quantum key distribution?

An article last month claimed that Toshiba Corp. and Tohoku University recently broke the record for the amount of data encrypted using quantum key distribution by transmitting "a few hundred ...
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Can we break RSA with an optical Fourier Transform?

We all known that RSA can be compromised using quantum Shor's algorithm. The horsepower underlying this algorithm is the Fourier transform. However, we can use alternatives to perform this function, ...
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Attacking AES-128 with Grover's algorithm

How many plain text / cipher text pairs are required by Grover's algorithm when it is used to try and discover a secret AES key? I am trying to determine if having a device which limits the speed at ...
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CHSH condition explanation

Can anyone explain to me (in simple words) what CHSH condition is (reference)? I'm wracking my brain in order to try to understand the meaning of the following expression: CHSH condition $a_i⊕b_i=...
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What happens after sharing the secret key in quantum cryptographic schemes to send the message bits?

As a person working on the physics perspective of quantum communication, I understand the process upto which the quantum key is shared securely. What happens after this process to send message bits? ...
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How does BB84 fare against an attacker who can entangle qubits?

Consider the following attack on the BB84 quantum key exchange protocol (as far as I can tell, it should work similarly for E91): After Alice sends her key bits encoded in qubits with randomly chosen ...
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What are the current known weaknesses/attacks on quantum key distribution?

I am writing a paper on the implementation of QKD in the future. I want to know if there are any viable attacks on the BB84 protocol or QKD in general? I know of the Photon Number Splitting attack or ...
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Are biases narrowed towards the provenance of hard NP complete problems relevant?

I hear of randomized reduction, deterministic reduction and non-deterministic reduction of complexity from A to B problems. This could make things impossible for polynomial time adversary prying into ...
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How to find the inverse of f(x) in NTRU key generation?

I work on a project that depends on the NTRU cryptosystem, but I don't know how to find the inverse of $f(x)$. Please see the picture: Please help me to understand this problem.
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How effective is quantum computing against elliptic curve cryptography?

I've been reading the Wikipedia page on Elliptic-Curve Cryptography and I came across the following. in August 2015, the NSA announced that it plans to replace Suite B with a new cipher suite due ...
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What is Quantum Cryptography?

When it comes to exchanging secure information over an insecure channel, this approach is considered. It all depends on the nature of photons in which the third polarization is focused. It can easily ...
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Is this man in middle atack possible in quantum cryptography? [duplicate]

Lets consider there is channel between Alice and Bob, sequered with quantum cryptography. To put it simple, Alice is left, Bob is right and the quantum states are 'up' ~ U and 'down' ~ D. Alice ...
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What role plays Quantum Fourier Transformation in Shor's integer factorization algorithm?

I cannot seem to understand the role or goal of Quantum Fourier Transformation in Shor's integer factorization algorithm. Is it used to collapse all quantum states into one, in which it has a factor ...
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Is ekert91 more secure than BB84?

I'm studying quantum cryptography and my question is "simple": Is the use of entangled states, like in the Ekert91 protocol, more secure than using not-entangled states like the BB84's ones? Is ...
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Can AES be broken by factorization (using Quantum Period Finding)?

I am trying to understand the paper "Breaking Symmetric Cryptosystems using Quantum Period Finding", and I reckoned the paper is roughly implying to break secret-key cryptographic system by finding ...
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Would Zero Knowledge Proof (ZKP) remove the need for Quantum Key Distribution? (QKD)

Would Zero Knowledge Proof (ZKP) remove the need for Quantum Key Distribution? (QKD) Since we no longer need keys to be passed around?
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what benefits quantum offer over classical parallelism

What is the benefits of quantum computing vs parallel processing using classical computer ? Can classical parallel processors outperform quantum computing ?
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Practical quantum attacks on AES - Is AES-128 used in a block mode vulnerable to attack using quantum algorithms

Can Grover's (or similar) algorithm be used to attack AES-128 when used in cipher modes like CTR? It seems like the answer is no... Also I have a similar question for SHA256 when used for a MAC. It ...
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Practical quantum attacks on SHA256 MAC and HMAC

Is SHA256 MAC (or HMAC) vulnerable to any quantum attacks? Game setup: The attacker's goal is to produce a valid MAC to be accepted by other devices in the ecosystem. The ecosystem consists of ...
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Is post-quantum Oblivious Transfer possible

If I’m not mistaken classical OT is not regarded quanum-safe. However I’ve been reading (not really understanding) some papers [1,2] and some reviews[3] on quantum OT and/or post-quantum OT, it seems ...
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Dice vs quantum random number generator

I recently championed quantum key distribution networks. This has led me to also question quantum random number generators. It appears that randomness is randomness, even if made by custom quantum ...
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Need an XL Algorithm example

could anyone give me a small example with actual numbers and variables over a finite field of how the XL algorithm is used to solve overdetermined systems? And the steps involved. I understand the ...
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What happens when quantum-resistant cryptography is implemented using a quantum computer?

What happens when quantum-resistant cryptography is implemented using a quantum computer? Give the whole deal with the qubits, is this even a worthy action?
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Is E91 safer than BBM92?

I would like to compare the security of these two QKD protocols which both use entangled photons that are distributed between the users Alice and Bob. In the case of E91, the photon is measured ...
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What is post Quantum Cryptography?

Post-quantum cryptography is cryptography under the assumption that the attacker has a large quantum computer; post-quantum cryptosystems strive to remain secure even in this scenario. Post-quantum ...
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Can public key cryptography survive quantum computers? [duplicate]

Quantum computation is based on the superposition principle of quantum physics. Bits in a normal computer are either 0 or 1. Quantum physics allows bits to be in a superposition of 0 and 1, in the ...
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Conjugate variables in Quantum Key Distribution?

According to Heisenberg's Uncertainty Principle, it is impossible to measure the values of conjugate variables simultaneously as measuring one accurately would make the other equally corrupt. So in ...
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Can quantum computers break quantum cryptography?

I happened to learn that encryption by quantum cryptography would be impossible to break as it's state changes the instant of an eavesdropping event(by non-quantum systems) occurs. But I'm not sure if ...
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The quantum key establishment protocol

Consider the quantum key establishment protocol. Assume that bit values, emitter basis, and receiver lter orientation are selected independently and uniformly at random (i.e., 50% chance for each of ...
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Quantum Cryptography Used in a messaging application

Is it possible to create a messaging application and apply a quantum cryptography technique to encrypt the messages between two parties within the application?
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Quantum key distribution

Is there a minimum limit for No. of photons that Alice would send to Bob in a QKD scheme like BB84? If not than what would be a desirable length for initial qubit string?
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Is full Homomorphic encryption quantum resistant?

Since most of our asymmetric encryption algorithms are going to be out-of-date in a couple of year due to Shor's algorithm, I was wondering about the future of FHE schemes. I have found this paper, ...
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Understanding Quantum Key Distribution

I have watched dozens of videos on YouTube talking about Quantum Cryptography and how the BB84 algorithm works. However none of them bothered himself to explain how quantum key exchange process works ...
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Can quantum money exist?

Can a quantum money system exist in which bank (who possesses a secret key $k$) can create quantum states $S$ that anyone (in possession of public key $P$) can verify was issued by the bank without ...
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Attacks on Aes (128-192-256) [duplicate]

I have a direct question Is there any practical attacks on the AES cryptosystem (128-192-256 keys)
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Quantum algorithm encrypting classical data

Are there schemes for encrypting classical ciphertext using quantum algorithms? Specifically, if a public key system exists for classical data, and classical ciphertexts, can this scheme be ...
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Post quantum zkSNARK?

Do there exist any zkSNARK constructions that are based on post quantum cryptography? The encryption scheme used in the zkSNARK that is employed in Zcash for instance uses an encryption scheme of the ...
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Differences between Single photon QKD system (BB84) and EPR photon-pair QKD system (BBM92) for quantum public key distribution?

What are some differences between Single photon QKD system (BB84) and EPR photon-pair QKD system (BBM92) for quantum public key distribution?
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Cryptocurrency for quantum computers that is physically impossible to double-spend?

Could a cryptocurrency running (at least partially) on a quantum computer (and/or on a quantum network) be developed in which it is physically impossible to double-spend? In other words, a coin in ...
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How do quantum key distribution systems tolerate noise?

It seems to me that any noise in the signal would result in Alice and Bob generating different keys, without a simple way to tell the difference. How do quantum key distribution systems tolerate ...
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Shor algorithm for discrete log and periodic function

I am about the following well known problem: Let $p$ is a prime number, $g$ is a generator of $(\mathbb{Z}/p\mathbb{Z})^\times$, $b \in (\mathbb{Z}/p\mathbb{Z})^\times$. Find $x$ - an integer such ...
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Router for Quantum key distribution

As far as I know QKD needs a quantum channel to send the photons. If anyone measures the photons they are useless. It sounds as if Alice needs a fiber optic cable all the way to Bob - or at least ...
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BB84 Why does Bob generate a random key?

I am quite new to this stuff so this question might be trivial. I was reading about bb84 and, as I understood it, after Alice sends $\psi$ Bob chooses a random sequence $b'$ and makes a measurement in ...
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Why still we are using classical key exchange rather than quantum idea

Why still we are using Diffie-Hellman idea rather than BB84 or B92 like quantum protocols for key exchange?
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Is AES256 the most secure encryption algorithm available at the moment? [closed]

I have had to edit this question because it was too broad (sorry didn't realise that was not allowed...), so, lets go with: Is AES256 the most secure encryption algorithm available at the moment? If ...