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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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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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1answer
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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 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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0answers
60 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 "...
2
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1answer
99 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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3answers
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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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0answers
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Why do we need 2X input bits in the circuit of Shor's quantum Algorithm? [duplicate]

The text that I am following to understand the factoring algorithm states that we need $m = 2\cdot\log(N)$ input qubits because we need to evaluate the oracle function for at least $N^2$ times. Please ...
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0answers
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Ambainis quantum collision-finding alg; triple hash output lengths?

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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3answers
543 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 ...
2
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1answer
156 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
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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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1answer
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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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0answers
259 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 ...