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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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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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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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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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Is using quantum computing to break passwords non-sense?

I understand the concept of 'trying all possibilities at once' but can anyone explain this with respect to the fact that my PC only accepts one password at a time? There's no input field that accepts ...
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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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344 views

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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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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2answers
581 views

Attacking AES128 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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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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46 views

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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172 views

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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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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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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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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210 views

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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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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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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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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Are hash functions strong against quantum cryptography and/or independent enough of mathematics?

I work on ethereum and other blockchain technologies. And seeing that quantum pc's are someday going to see the light I have some questions / doubts. I was wondering if hash functions are strong ...
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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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95 views

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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Using XL Algorithm to solve overdetermined systems, simple example required

Can someone give a small example of how the XL algorithm is used to solve an overdetermined system, with numbers and variables along with the steps if possible as apposed to just a general case? This ...
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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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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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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 ...
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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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How can Shor's Algorithm be applied to ECC?

I have not found a specific answer to this question on here. Shor's algorithm can be used to factorize a large (semi)prime $N$ by reducing the task to period-finding of a function $f(x)=x^a$ mod $N$. ...
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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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532 views

Shor's algorithm for elliptic curve discrete logarithm problem

Could you write Shor's algorithm for solving the discrete logarithm problem and how it could apply to elliptic curves in a few, easy to understand steps? I have a basic understanding of quantum ...
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108 views

Confusion about security of quantum key distribution

In Quantum Key distribution, it is my understanding that when Eve tries to intercept photons being sent from Alice to Bob, she has a 50% chance of using the correct polarization filter, and so 50% ...
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What makes Quantum Cryptography secure?

This is my current understanding of how Quantum Cryptography works: (The first bit is Quantum Key Distribution) Alice sends a beam of photons to Bob through a quantum channel such as an optical fiber....
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what is the motivation behind quantum key distribution with Continuous variable?

Quantum Key Distribution protocol is a technique that allow two parties to share common secret key for cryptographic purpose and defined as being secure, by definition. But I am still wondering what ...
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How exactly works the quantum communication done by China?

This video and this article announced that spacial quantum communication were finally done using satellites. As a recap, when two particles are entangled, if a measurement is done to one of them, ...
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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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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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Is quantum cryptography unbreakable?

People always say that "there is no such thing as unbreakable crypto!" In most cases they are right. AES, RC4, RSA, C25519, DH, .... are all cryptographic algorithms which are crackable (with extreme ...
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What exactly is a quantum key distribution network for?

There are many diagrams out there explaining how quantum key distribution works on a physics /optics and mathematics level. I understand these explanations fairly well so I'm not asking about the ...
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Is quantum randomness different to conventional randomness?

I've been reading a question regarding the uses of quantum computing. There is a broad theme throughout the answers that seems to suggest that randomness generated via quantum means is somehow better ...