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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Reusing same source for single-source randomness extractor

Let $ext$ be a single-source randomness extractor which takes a $d$-bit seed and a $n$-bit source as input and produces a $m$-bit output. Suppose we have a source $X$ with min-entropy $k$. Is it ...
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Use of randomness in an Elgamal like encryption

Suppose I have the following encryption scheme: for a message $m\in\mathbb{F}_p^*$, I generate the ciphertext = $(g^r,f^mh^r)$ where $g$ is the generator of a cyclic group $G$ of unknown order $n$ and ...
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200 views

Feasible way to check n-dimensional equidistribution of PRNGs

I am currently gathering some test methods and test suites for random number generator qualities, and am a bit stuck at finding something feasible to test for n-dimensional equidistribution. As input ...
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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 ...
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Can Verifiable Random Functions be used to pick a random node from a pool?

Let's say that I have a decentralized system and I have a list of nodes published on a public log like a blockchain. I want a node A to be able to connect to ...
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64 views

Is the number still a CSPRN if we only allow an interval from a CSPRNG?

tr -dc 0-9 < /dev/urandom | fold -w 3 | awk '$0>=100 && $0<=200' What this line does: /dev/urandom (Linux) is proven to be a CSPRNG, that is ...
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107 views

Special random distribution algorithm

I am implementing ring signatures as a part of an authorization system. Since the number of users could get high enough to make computation on end-user devices infeasible, I am thinking of "...
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44 views

What is a “set synchronized CSPRNG”?

I'm looking to implement a performant revocation method for JWTs. I'm reading a paper, in which the following section's second paragraph states: If we use the client hashing approach described ...
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Would the result of encrypting weak random data via AES-128 with a CSPRNG-generated key be considered strong/secure random data?

I am trying to understand the security implications of using a well known block (or stream but in this example block) cipher like AES-128 to produce pseudo-random data. My specific question is would ...
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59 views

Why does a “never-repeating” nonce limit a key to safely encrypt only a single block?

This questions comes from a section outlined in RFC 5297 on SIV-AES. The paragraph in particular outlines the idea of a never repeating nonce vs an "almost always" non-repeating nonce. If the nonce ...
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OTP Random Pad Renewal Without Extending Message

So I recently learned about the concept of a One Time Pad; and I from what I understand it means that if a XOR key is completely random and equal to or longer than the plaintext, it makes it so that ...
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75 views

Randomness Test of Permuted Sequence

As we can generate a permuted sequence using KEY in KSA (Key Scheduling Algo) of RC4. Is there any way to check the randomness of the permuted sequence? Let say I created 100 different permuted ...
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What is fixed randomness and unfixed randomness?

I have found these notions recently in an article. What is fixed randomness ? What is unfixed randomness ? Link of the article : http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.431.9034&...
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How Are Linear Congruential Generator Multipliers Chosen?

There are several numbers that keep coming up when looking at certain random number generators, for example 6364136223846793005 is used in newer pcg-family algorithms and seems to draw it from ...
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Is there an algorithm or protocol that allows to securely generate random shuffles when two parties are not colluding without a sever side seed?

I am building an app that pits one party against another party in a gambling transaction – both parties have competing interests and have an incentive not to cheat the other party. I am looking for a ...
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Beginners question about revealing randomness in probabilistic asymmetric encryption

I am encrypting "1" with probabilistic encryption with a foreign public key (I don't have the private key for it) which results in an encrypted file e. Can I prove to a third party, that e contains ...
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RIsk mitigation: block cypher vs xor

It sort of looks like to me that there is a kind of risk mitigation in the architecture of block cyphers vs the xor cypher. In XOR, the risk is entirely in the random number generator. The XOR ...
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Fuzzy Extractor: Order of elements in set

Does order of elements in two sets matters to authenticate using Fuzzy Extractor? Using extractor as proposed in https://www.cs.bu.edu/~reyzin/fuzzy.html it seems the set difference is zero for this ...
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496 views

Relationship between “Entropy” and “Security” in crypto functions

There is a lot of confusion between "entropy" and "security" of a cryptographic function. I like to visualize it as the entropy being the water, and the crypto function being a glass. So for ...
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Does RSA_PRBG security depend on keeping seed secret?

The HAC provides a PRBG using RSA (Chapter 5 p.185): It appears the seed must be kept secret if $e$ is a well known value. If $e$ is uniformly distributed between 1 and $\phi$, then the seed does not ...
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205 views

PHP predicting array_rand

Given the following PHP code (assuming PHP 5.6.x): ...
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98 views

To prove $r_2$ is a uniformly at random value in $Z_n$, where $r_2=r_1 . m$

$m$ is arbitrary value in $Z_n$, where n is RSA modulo. Then we do: $r_2=r_1 . m (modn)$, where $r_1$ is a random value such that $r_1\in Z^*_n$. ** Question(1): is $r_2$ a uniformly at random ...
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Interpretation of (NIST) Non Overlapping Template Matching Test

Regarding the Non-Overlapping Template test, this test normally gives us a bunch of p-values (148 values). I would like to ask that how do we interpret those values into a single p-value for ...
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RNG randomization strength for PRF seed

Consider a use case that requires the creation of multiple asymmetric key pairs. There are two options for generating random seeds for a PRF: Use a software based RNG and generate a new seed for each ...
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What is the probability that a random function is invertible?

Having a random function - $R\in{}\mathcal{R}$ s.t. $R:\{0,1\}^n\rightarrow{}\{0,1\}^n$. What is the probability that $R$ is invertible? I know calculating it suppose to be straight forward, but I'...
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Understanding a claim made by NIST SP 800-22 on the possibility of calculating $\beta$, the probability of error type 2 in a hypothesis test

NIST SP 800-22 on page 1-4 (that's page 16 of the PDF) states the following. Pay attention to the bold passages. (Emphasis are mine.) Are they true?! Can you advise? One of the primary goals of ...
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How to save an encryption key to a binary file to be used in NIST STS

I wrote a simple logistics function that i use for my pesudo random number generator.I want to test it's randomness so i downloaded a custom windows version of NIST STS. the program rqeuires you to ...
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59 views

Crack LCG given 2 output values only

I want to try to break an LCG generator just as programming practice task. I found similar issue at Cracking a linear congruential generator. Assume that m is given. The answer to the link above ...
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Prove that a given signature scheme is secure under random message attacks

This is a follow up to my previous question. Consider the following signature scheme: $\operatorname{KeyGen} (1^k$) : On input of a security parameter $k$, choose a symmetric bilinear group with $e : ...
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Difference between public coin and common coin?

What is the difference between public coin and a common coin? I often see both appearing in the literature, but I cannot explain myself, whether they are the same concept or not.
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Lsb as hard core predicate in a sign-hash scheme

Given a random oracle and a deterministic signature scheme. Is the following $hc(x)$ an hardcore predicate of $H(SIG_k(x))$ ? $$hc(x)=lsb(H(SIG_k(x)))$$ How would I get to think about this? I saw a ...