Questions tagged [quantum-cryptanalysis]

Use this tag on questions about attacks that break cryptographic guarantees / security properties of primitives and protocols and utilize quantum computers as an essential part.

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136 views

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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3answers
193 views

Is there a quantum-safe time lock?

Most successive squaring time lock puzzles I've seen appear to be broken by Shor's algorithm. Is there another practical and efficient time lock protocol that is not broken by Shor's algorithm? If not,...
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1answer
129 views

Breaking ciphertext using a quantum computer when the public key is not available

As we know about Shor's algorithm on quantum computers it is possible to crack RSA / ECC easily if we have enough qubits. Is it possible to crack RSA / ECC on a quantum computer if we only have ...
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1answer
81 views

Can quantum algorithms solve the approximate GCD hard problem efficiently?

Some cryptographic schemes are based on the hardness of this problem. The answer to this question determines if those schemes are quantum resistant or not. There are a number similar questions but ...
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2answers
153 views

what does output parameters of lwe estimator stands for?

I want to use lwe estimator to find classical and quantum security of my proposed key exchange protocol. On this website, I want to understand the output of sage code on lwe estimator given bellow. ...
2
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1answer
203 views

Is using AES-256 with a key of less than 256 bits of entropy still quantum-resistant?

Encrypting with AES-256 is widely claimed to be post-quantum secure. But let's take a case where you use an initial key that has less than 256 bits of real entropy. In this example, let's work with a ...
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0answers
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How would quantum computers affect password based encryption?

At first glance: Assuming that the output of the password hashing function is large enough, quantum computers should have no effect on password encryption as on symmetric cryptography in general. Is ...
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1answer
4k views

How does IBM's 53-bit quantum computer compare to classical ones for cryptanalytic tasks?

IBM just announced "a new 53-qubit quantum computer". How does it compare to classical computers, performance-wise, for cryptanalytic tasks? E.g. finding a 48- or 64-bit value whose SHA-256 has a ...
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1answer
182 views

Are there post-quantum cryptosystems with a gap between classical and quantum security?

Is there a gap between classical attacks and quantum attacks against some post-quantum security assumptions? (I'm particularly interested in asymmetric cryptography.) I understand that there is no ...
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2answers
251 views

How Will Quantum Computing Change Cryptography's Future? [closed]

Quantum computing is at the intersection of math, physics, and computer science. It seems so complicated that only large organizations could build such algorithms and have their own quantum computing ...
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0answers
52 views

Finding the period of a function with a single output qubit - impact on RSA

In this paper,May and Schlieper claim that one can find the period of a function $f()$ by embedding $h \circ f = h(f(x))$ for input $x$. This would have the immediate consequence of reducing the ...
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1answer
626 views

Is this paper's technique for factoring RSA 2048 with noisy qubits realistic?

A paper titled How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits has just come out which proposes a technique to factor RSA keys with moduli up to 2048 bits with a design ...
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Does the block size of a symmetric cipher impact the security of the cipher itself? [duplicate]

Will a 128 bit block have some security implication in post-quantum cryptography?
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487 views

Can Shor's algorithm factor multi-prime numbers?

I know that Shor's algorithm can factor semi-primes ($N = p \times q \space, \{p, \space q \in \Bbb{P} \space \vert \space p, \space q \gt 0 \} $). Assuming that all prime numbers are so large that ...
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Time-memory tradeoffs in Shor's algorithm

Can a quantum computer with insufficient qubits to factor an integer of a given size make any progress in factoring it? For example, what if a quantum computer is only one qubit short of what is ...
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2answers
106 views

Does a thermodynamic limit on key search apply to quantum computers?

There is (or at least was) a thermodynamic reasoning that any form of brute force key search would require an energy at least $k\,T$ per key tested, where $k$ is Boltzman's constant and $T$ the device'...
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1answer
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Combining classical attacks and quantum cryptanalysis

I'm regularly reading that AES-256 is secure against quantum computers because Grover's algorithm will only halve the key strength (i.e. "only" require $\sqrt{2^l} = 2^{l/2}$ operations instead of 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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2answers
3k views

Can quantum computers put computer security in jeopardy?

There are many articles about quantum computers describing how powerful they are in computing and that they can solve very complicated equations in a short time. One of the biggest security measures ...
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108 views

How many qbits are required to break Diffie-Hellman over a multiplicative group

There have been comparisons between RSA and ECDH with regards to the number of qbits (qubits) required to break the algorithm with a specific key size. But how many qbits are required to break "...
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1answer
164 views

Will using large keys with Classic cryptographic algorithms beat quantum computers?

This is a purely theoretical question. Everyone is talking about quantum cryptography being the next big thing as quantum computers will be much faster than the computers we have today. So, from my ...
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2answers
5k views

Largest integer factored by Shor's algorithm?

I'm studying Shor's quantum factoring algorithm. I was wondering what the largest integer is which they were able to factor with a small quantum computer. Does anybody has an idea about this?
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1answer
169 views

What are the implications of quantum collision search algorithms like Ambainis for collision-resistant hash functions?

I just stumbled onto a series of 2017 papers about applying the Ambainis quantum collision-finding algorithm to hash functions. (disclaimer: I haven't read all of them in full yet): Post-quantum ...
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4answers
860 views

What telltale signs would indicate that quantum computers are about to become dangerous to classical cryptography?

What would be telltale signs that quantum computers become imminent and sizable danger to classical cryptography in commercial applications ? Make classical cryptography consist of symmetric ...
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1answer
279 views

Why is the number of qubits used in Shor's factoring algorithm so high?

When preparing the initial state of the algorithm to factor $n$ he computes $q = 2^l$ such that $n^2 \leq q < 2n^2$. The first register then contains $l$ qubits. Why does this need to be so high. ...
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1answer
202 views

it is possible to use quantum algorithm search (Grover's algorithm) for new searching strategies for differential and linear attacks

I am trying to use Grover's algorithm to find Differential characteristic of Feistel and SPN structures block ciphers. basically, which is Finding a good differential characteristic with high ...
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Real world performance of (still theoretical) Grover's Algorithm

Grover's Algorithm is a quantum algorithm for searching "black box" functions and could be used to reduce the search space for things like symmetric ciphers and hashes by as much as half (quadratic ...
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444 views

XTS-AES-128 and Grover's algorithm

AES-128 is considered weak against quantum computers because Grover's algorithm effectively halves its key length to unacceptable 64 bits. XTS-AES-128 as described in IEEE 1619-2007 doubles key ...
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3answers
5k views

Applicability of IBM's projected 50-qubit quantum computer Q to cryptanalysis?

IBM announced Q, a project for a 50-qubit universal quantum computer, according to the press realease. Here is more PR spin, and the research sub-page. What would be the applicability of that to ...
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168 views

Space complexity of quantum collision search?

Is there a known way to reduce the space complexity of quantum collision search (PDF) beyond what is offered by the built-in time-space tradeoff, while keeping the time complexity significantly below ...