Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

Questions tagged [cryptography]

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

Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks.

Reference: https://en.wikipedia.org/wiki/Quantum_cryptography

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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 with the bit size of the key. An example for that is…
peterh
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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 quantum computers (hence use quantum cryptography),…
PiMan
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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 are most likely not efficiently solvable by a…
M. Stern
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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 could function. The article's conclusion states…
Daniel Burkhart
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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 aware about BB84, but it only seems to be a partial…
Be Brave Be Like Ukraine
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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 choice of a generic structure - a data engineer can…
Daniel Burkhart
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Does quantum computing threaten blockchain?

As per Wikipedia, blockchains are a way to maintain "a continuously growing list of records, called blocks, which are linked and secured using cryptography [... and] inherently resistant to modification of the data." Blockchains are in current…
Daniel Tordera
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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 following density matrix: $$\rho = .5 |0\rangle…
QuestionEverything
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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; it possible to have a speed up using more than…
kelalaka
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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 I went to work on exercise 2.9 and 2.10. Ex. 2.9…
Sam
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Can a quantum computer break quantum cryptography?

I’m not sure if this makes sense, but I know that there is quantum and post-quantum encryption, and I’m curious whether quantum computing can break a quantum encryption.
Gejolop
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Rigorous security proof for Wiesner's quantum money

In his celebrated paper "Conjugate Coding", Wiesner proposed a scheme for quantum money that is unconditionally impossible to counterfeit, assuming that the issuing bank has access to a giant table of random numbers and that banknotes can be brought…
Didix
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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 Bob. The countermeasure against this potential…
Bruno Rijsman
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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., 2014). Slides available here. I don't fully…
user1936752
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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 quantum blockchain which leverages time entanglement…
user820789
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