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Questions tagged [cryptography]

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

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What does teleportation have to do w/ XOR linked lists?

I am trying to wrap my head around the correlation between repeating teleportation & XOR linked lists. I understand that: "the quantum equivalent of the one time pad (i.e. XORing a message with ...
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1answer
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How are nonlocal games used in device-independent quantum cryptography?

As I understand it, device-independent quantum cryptography enables you to safely perform cryptographic operations without necessarily trusting the quantum device on which they are performed. Nonlocal ...
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3answers
133 views

Density matrix after measurement on density matrix

Let's say Alice wants to send Bob a $|0\rangle$ with probability .5 and $|1\rangle$ also with probability .5. So after a qubit Alice prepares leaves her lab, the system could be represented by the ...
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BB84 protocol over LiFi

The question is already explained in the title, but I'm curious regarding the possibility to adopt the BB84 protocol over LiFi (in theory). Could it be possible or are there some limitations, such as ...
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How to encode a qubit in standard basis?

I wonder what the steps for encoding a qubit in a certain basis are (you can give your answer in terms of the standard basis for simplicity). Example and a little explanation about steps would be ...
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1answer
41 views

Comprehension questions on quantum cryptography especially BB84

I have recently read a lot about the BB84 protocol, I have used three primary sources, the original work, a QK book, and a diploma thesis. My questions refer to the photons sent by Alice, the base of ...
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1answer
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Lesser qubit computer doing the parts of Shor's against e.g., RSA-2048 sized prime

After posting this question to Physics, it became pretty clear I should have posted here. So: How might a (e.g.) 72-bit crypto-relevant quantum computer attack RSA-2048? Bonus: how might that be ...
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1answer
100 views

BB84 attack with entangled qubits example

BB84 attack with entangled qubits example Hi, I'am interested in an attack for BB84 protocol with entangled quibits. Lets say Alice sends a qubit $x$ in state $\left|1\right>_x$ to Bob and Eve ...
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1answer
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Quantum attack on hash functions

The line of questioning is inspired by the pick one trick in Section 4 of the PDF version of the paper Quantum Attacks on Classical Proof Systems - The Hardness of Quantum Rewinding (Ambainis et al., ...
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2answers
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Can we speed up the Grover's Algorithm by running parallel processes?

In classical computing, we can run the key search (for example AES) by running parallel computing nodes as many as possible. It is clear that we can run many Grover's algorithms, too. My question is;...
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1answer
103 views

How can Shor's algorithm be used to crack 32 bit RSA Encryption? [closed]

I have this as my minor project and plan to use Shor' Algorithm for factorization to figure out the $p$ and $q$ factors for cracking. Although I understand the theoretical part, I am having some ...
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1answer
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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 ...
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1answer
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How many qubits does it take to break a 10 characters password?

Let's assume we developed a hashcat-like programs for quantum computer. How many qubits we need to find the correct hash (WPA, MD5,...) from a 10 characters password make from upper, lower & ...
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1answer
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How many bits do Alice and Bob needs to compare to make sure the channel is secure in BB84?

I was trying to self-study qmc by reading the Quantum Computing A Gentle Introduction book, in section 2.4 it talks about the quantum key distribution protocol BB84. After (I thought) I understood it ...
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0answers
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Are non-secret-based quantum money mini-schemes susceptable to Jogenfors' “reuse attack?”

Aaronson and Christiano call public-key or private-key quantum mini-schemes $\mathcal M$ secret-based if a mint works by first uniformly generating a secret random classical strings $r$, and then ...
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1answer
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Can quantum money be reliably “burned?”

One of the novel features of Bitcoin and other cryptocurrencies is that coins can be irrefutably "burned" or destroyed, by creating a transaction to send the money to a junk burn address. Thinking ...
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2answers
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What measures can be taken against attacks on cryptosystems by quantum computers other than just classifying research?

If quantum computers advance to the point where they can defeat RSA, DSA, SHA (and really all existing classical public key encryption or and authentication) then it appears that it would be ...
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1answer
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What classical public key cryptography protocols exist for which hacking is QMA complete or QMA hard?

Such a public key cryptosystem would be "quantum safe" in the sense that quantum computers cannot efficiently solve QMA hard problems.
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2answers
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How to justify post quantum encryption security?

Is there some definition or theorem about what a quantum computer can achieve from which post-quantum cryptographic schemes (eg lattice cryptography, but not quantum cryptography) can justify their ...
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224 views

Time Entangled Quantum Blockchain

This answer cites a paper[$\dagger$] which purposes a quantum blockchain using entanglement in time. "The weakness is that the research only presents a conceptual design." - QComp2018 How could a ...
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2answers
2k views

Is quantum cryptography safer than classical cryptography?

Quantum computing allows us to encrypt information in a different way compared to what we use today, but quantum computers are much more powerful than today's computers. So if we manage to build ...
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1answer
106 views

BB84 Protocol Alice Choice to Bob

The image is taken from this link. Here Alice is using random bases to encode 0 or 1. After the process is completed, Bob has similarly polarized photons as Alice. These polarization can be any of ...
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2answers
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'Rectilinear' and 'Diagonal' Basis in BB84 Protocol

A lot of the tutorials on BB84 protocol talks about these two measurement bases, 'Rectilinear' or 'Vertical-Horizontal' and 'Diagonal'. I understand that it is possible to create a physical device ...
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372 views

Quantum computing and blockchain technology

It is popularly stated that quantum computing could destroy and disrupt blockchain technology completely. How is quantum computing a threat to blockchain technology?
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How can we reliably know if a key size is still safe to use as new quantum computers are created?

I've heard that quantum computers pose a major threat to 1024 bit and possibly even 2048 bit RSA public-private key cryptography. In the future however, bigger size keys will probably become at risk ...
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2answers
239 views

Rigorous security proof for Wiesner's quantum money

In his celebrated paper "Conjugate Coding" (written around 1970), Stephen Wiesner proposed a scheme for quantum money that is unconditionally impossible to counterfeit, assuming that the issuing bank ...
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1answer
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How would Blockchain technologies change to survive a post-quantum world? [closed]

Reading this entertaining piece of a QC enthusiast mining bitcoins with a Quantum Computer (although efficiently mining bitcoins with the current state of QCs is far-fetched, it is quite possible to ...
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Will post quantum crypto come soon enough? [closed]

The main reason to start with Post Quantum Crypto (PQC) right now is because creating strong crypto, good implementation and accepted standards takes very long. Right now, most PQC is in the 'crypto' ...
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1answer
222 views

Quantum Bitcoin Subdivision

Background Recently I was reading the article "Quantum Bitcoin: An Anonymous and Distributed Currency Secured by the No-Cloning Theorem of Quantum Mechanics" which demonstrates how a quantum bitcoin ...
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2answers
272 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 ...
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1answer
179 views

Are there any encryption suites which can be cracked by classical computers but not quantum computers?

Are there any encryption suites that can be cracked by usual computers or super computers, but not quantum computers? If that's possible, what assumptions will it depend on? (Factorizing big numbers, ...
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2answers
231 views

Blind Quantum Computing Generic Structure Variable Selection

Background Recently I came upon a research article entitled Experimental Demonstration of Blind Quantum Computing. Within this research article, the scientists claimed that - through the proper ...
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2answers
210 views

How is quantum cryptography different from cryptography used nowadays?

Recent researches indicate that quantum algorithms are able to solve typical cryptology problems much faster than classic algorithms. Have any quantum algorithms for encryption been developed? I'm ...
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4answers
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Is it possible for an encryption method to exist which is impossible to crack, even using quantum computers?

Quantum computers are known to be able to crack in polynomial time a broad range of cryptographic algorithms which were previously thought to be solvable only by resources increasing exponentially ...