# Questions tagged [randomness]

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

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### Is the product of two NONZERO elements independently drawn from a prime field uniformly distributed?

Let $\mathbb{Z}_p$ be a prime field, $a, b$ be two random elements independently drawn from $\mathbb{Z}_p^*$, and $$c = a* b \mod p,$$ is $c$ uniformly random? and why? How is this question related ...
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### Does the permutation cycle of a PRNG change completely with different seeds?

Apologies if this seems like a trivial question. I've been learning PRNG and cryptographic basics and I don't think I've found an answer to this question (At least that I understand). My understanding ...
1 vote
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### Generating random numbers in MPC, but the upper bound remains secret

Suppose we are using secret sharing-based MPC over a prime-order field. Given shares of a secret integer $s$, is there a way to generate shares of uniformly random integer in $[0,s)$ such that $s$ ...
1 vote
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### Key generation from partially random data

Suppose an embedded system without a true random number generator peripheral, but nevertheless it is necessary to generate a secret key. Suppose also that this embedded system has an analog-to-digital ...
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### How 7z zip is able to decrypt a file that had the exact same input data and same password, if the encrypted file is different every time? [duplicate]

how does 7z perfectly "restores" the missing random encryption key parts used to generate the different encrypted file? I watched this in a loop. Every time the encrypted file contents ...
867 views

### CVE-2024-31497, nonces and random numbers: Can someone explain, please?

Regarding CVE-2024-31497 a German article "Nur NIST P-521 betroffen: PuTTY-Lücke kompromittiert private SSH-Schlüssel" wrote something about a vulnerability in PuTTY. The issue was claimed ...
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### What is better source of random bytes: Yubikey or /dev/random (or both)? [closed]

Let's say I need to generate a key, I have these three options as to where to get random data: Yubikey (gpg-connect-agent 'SCD RANDOM 16384' /bye) ...
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### Deriving a cryptographic PRNG from a publicly random sequence

Consider a model of computation where we have a public oracle that provides access to a random sequence $R$. Given an index $i$ the oracle returns either 0 or 1, with the responses being deterministic,...
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### Why are most ABE KeyGen algorithms probabilistic algorithms?

It seems that in most Attribute Based Encryption schemes, the keygen algorithm is probabilistic, which means that given the same public key, master secret key and attribute set (or access structure), ...
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### Why are most KeyGen algorithms constructed to be probabilistic algorithms?

Are deterministic keygen algorithms unsafe? Why?
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1 vote
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### How to instruct VeraCrypt to use my hardware entropy source

As a hobby I built a radioactive decay based RNG, that I am still perfecting. I would like to know how to use its output to contribute to VC entropy pool for key generation. I know that before ...
77 views

### Can a PPT adversary get secret $a$ from public messages $m_i=x_i-a \mod p-1$ for i=1,2, ...,n?

Consider I have a secret $a \in Z_P^*$ and n public messages where $m_i=x_i -a \mod p-1$ and $x_i \in Z_p$ for i=1,2, ..., n. Given that $a$ and $x_i$ for $i=1,2, ..., n$ are secrets, can a PPT ...
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### Interpretation of the Result of Dieharder Battrery of Tests: Very High p-value Result in rgb_lagged_sum Test in Dieharder Results in "WEAK" Assesment

I'm currently testing the randomness of using SHA-256 in Hash_DRBG mechanism based on this research. The parameters used in the testing are the default parameters, except for when the PRNG fails a ...
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### How good is blake3 compared to a random oracle?

How good is blake3 for generating pseudo-random bitstrings in comparison to a random oracle? Let's say we generated an arbitrarily long pseudo-random bitstring by concatenating blake3 hashes together ...
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### Judgment of Results from NIST Randomness Testing

I am using the NIST suite to test the randomness of binary numbers and I have a 64KB dataset. I am confused with the results in finalAnalysisReport.txt. I have the ...
107 views

### Generating UUID from Keccak-256 hash

Is generating Keccak-256 hashes with timestamp + nonce (ensured to be unique for each run), and taking its most significant 16 bytes sufficient to generate random V4 UUIDs? Obviously the 13th hex ...
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1 vote
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### The security of using a digital signature scheme twice with randomness

Suppose $\Pi=(Gen,Sign,Vrfy)$ is a secure signature scheme, is the following signature scheme $\Pi'$ secure? $Gen'$: The same as $Gen$, output public-private key pair $pk,sk$ on input $1^n$ $Sign'$: ...
1 vote
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### If G is a PRG, is G' necessarily a PRG?

Given: A function $$G: \{0,1\}^{3n} \to \{0,1\}^{6n}$$ which is known to be a secure Pseudorandom Generator (PRG). A derived function G'(x_1 \| x_2) = G_b(x_1\|0^n\|x_2), \text{ where } x_1, x_2 \...
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### RSA random key generation [duplicate]

How RSA keys are tested for primality if they are random generated? I imagine this could be time consuming task.
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