Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [randomness]

Usage of randomness (i.e. non-predictable data, usually in the form of bits or numbers) for cryptographic purposes.

For generating random numbers, see instead.

549 questions
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What is the use of REAL random number generators in cryptography?

I understand the use of pseudo-random number generators. I am not getting mixed up between these and "real" random number generators. However, I don't understand for what a real random number generator is used. If it is not deterministic, how can it…
liamzebedee
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uuidgen has consistent 13th digit and it's 4

I ran uuidgen 10k times and noticed that the 13th digit is always 4. Why is that?
mafonya
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Is this truly a TRNG?

As an appendix for my bachelor thesis, I proposed a solution for a TRNG that uses JPEG images as entropy source. It's open source and available on GitHub. My question is: can this be really considered as a TRNG? Obviously I tried to create a TRNG…
Riccardo Leschiutta
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Proving von Neumann extractor correct

Von Neumann extractor works as follows: Suppose $C$ is a biased coin, with $p = P[C = 1] > P[C = 0]$ and let $b_1b_2\ldots$ be sequence of results by independent coin tosses. For $i \ge 0$ one observes $b_{2i}b_{2i+1}$. If the two bits differ then…
user1868607
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How to convert a set of sequential integers into a set of unique random numbers?

I have a set of sequential and non-duplicate integers which I would like to convert into a set of non-duplicate random integers. What I want to achieve is this - I have a list of sequential numbers like below [1, 2, 3, 4, 5, 6, 7, 8, 9] This list…
Suhas
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Exactly how bad is using 'mod' to clamp reduce numbers to a given range?

Let's say I'm naive and want to generate a random integer in the range [0, m), so I do the following: k = cryptographically_secure_rng() % m where cryptographically_secure_rng returns a random integer in the range [0,n). Obviously, assume m <=…
user541686
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Is a subset of a random set still random?

Suppose you have an infinite list of random bytes, and you select the first N bytes that correspond to printable ASCII characters. Is this list of N bytes still as secure (e.g. for the purpose of a crypto secret or salt) as accepting all of the…
jonleighton
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Weak physical random number generator/source - what is this?

Why physical random number source can be weak? I see two kinds of problems: it is hard to control it and make it resistant to some unwanted bias, but also deliberate attacks, it has normal distributuon, while we usually want to have uniform…
Tom
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NIST randomness test p values

I have a binary sequence of length $2^{20}$. I am using the NIST statistical test, assess. What should be taken for ./assess and How many bitstreams? in this test? In the final Analysis report, what p-values should be there to pass this test?
str
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Is there a definition of the pseudo-random sequences like PRG or PRF in cryptography?

I have learned the definition of PRGs and PRFs. As I know the meaning of pseudoreandomness. I think that the pseudo-random sequence and the truly random sequence are indistinguishable. I did not find a definition of the pseudo-random sequences. And…
Blanco
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How to efficiently generate a stream of independent, but biased random bits?

Usually, in cryptography, one is interested in debiasing a stream of independent (true) random bits, and several algorithms exist to do this. What about the converse? Let's assume I have a stream of independent and unbiased random bits at my…
cryptopathe
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How long random value is required in random masking method?

I heard that random masking method requires a random number whose length is as long as a message to be sent, but I’m not sure that. So, I'd like to ask about that. 1. Boolean masking : $ x_i \oplus r_i$ Assume that a message is $ (x_7, x_6, \cdots…
user2642459
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secretKey ⊕ (secretKey ≪ 1), is randomness lost?

A truly random secret key is run through a cipher secretKey ⊕ (secretKey ≪ 1) is randomness lost? As in, is the computational cost to guess the ciphertext from secretKey ⊕ (secretKey << 1) lower than the cost to guess secretKey?
lsh
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Computational Randomized Encoding in the hybrid proof

A computational randomized encoding scheme $(\textrm{RE.Encode}, \textrm{RE.Decode})$ works as follows: $\textrm{RE.Encode}(1^\lambda, C, x, r)$: takes as input the security parameter $\lambda$ in unary, a circuit $C$, the input string $x$, and the…
CryptoLover
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Advantage of Adversary against a simple function?

Attacker has to win following game by distinguishing that output was updated by a certain function or not? Attacker queries an oracle for the output. Oracle generates fresh 4 random bytes $a$, $b$, $c$, and $d$ and one random bit $x$. if $x=0$,…
elonnoe
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