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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Why Entropy to be defined as Joint Probability Distribution Sum?

From Stinson's book, during the demonstration of the following Theorem which says: $H(X,Y) \leq H(X) + H(Y)$, with equality if and only if $X$ and $Y$ are independent random variables. The author ...
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Java: SecureRandom.getInstanceStrong() vs new SecureRandom()

Given SecureRandom class is considered suitable for use in cryptography, I consider new SecureRandom() to be secure (funny term, ...
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Does Enc and Dec need to be a pseudo-random function for a scheme to be CPA secure?

I am currently going through past finals' questions as exercises for my exam and there are no solutions provided. The question I am currently doing is: Let ∏ = (Enc, Dec, Gen) be a CPA-secure ...
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Existence of algorithm predicting next bit in output sequence

Let $X = [0, 1]\cap \mathbb{Q}$, and let $f:X \rightarrow X$ be a chaotic map (i.e. the logistic map with rational parameter). My question is as follows, and is purely theoretical in nature. Pick ...
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How secure is it to use a 128-bit random seed to derive a 256-bit key for seeding key-pair generation?

We are developing an open-source peer-to-peer app, Mapeo, designed for users with low technical experience (and no email or phone) to collect data in offline environments. We are generating their ...
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Are PRNGs Key Derivation Functions?

PRNG is a mechanism to produce randomness from an initial random seed, so basically a way to derive more secrets from one secret. Looking at the Wikipedia entry for KDF you find In cryptography, a ...
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Is it insecure to make nonce using random number generator and hashing algorythm with secret key like HMAC?

I'm building a project on Arduino Mega microcontroller and I need some nonce generator for challenge-response exchange. But I failed to find some alphanumerical string generators. Then I came up with ...
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Is hashing random numbers generated from a TRNG enough to create a key? [duplicate]

Is hashing random numbers generated from a TRNG enough to create a key? Basically taking the output of something like a Lavarand and pass that through a hash function like sha-2. I guess at the end of ...
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DIY TRNG on an embedded system for Ethereum private key generation

I'm trying to build this Ethereum hardware wallet on a custom designed embedded system and I'm no expert. Googling around I found this Robust, low-cost, auditable random number generation for embedded ...
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Difference between Non-uniformly random and Uniformly random

I am reading up on Key Deriving Functions (KDF) and in a section of the Real-World Cryptographic book by David Wong, a comparison is being made with Pseudorandom number generator (PRNG). And one of ...
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Incrementing nonces vs regular nonces?

I have recently been studying up on the lorawan protocol for IoT devices. LoraWAN has a handshake, and then communication can commense. Messages are encrypted and MAC'ed. When encryption and MAC's are ...
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Generate unique random values for unqiue input values

I'm going to generate unique random values based per a range of unique input values. In other words I have range of input values which these numbers are part of a series (like a range of serial ...
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Does Endianness matter in NIST SP800-22 test?

I am curious about Randomness test suite. One of the famous randomness test suite, DIEHARDER, said that Endianness does not matter for a "GOOD" random generator. Note that this is not the ...
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Mersenne twister word size and degree of recurrence combination

For a 32-Bit variant of Mersenne twister, if the outputs Should be a 5-Bit integer(word size) then what is the value of recurrence according to the k-distribution?
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Neural Network based on pseudorandom number

Recently, I read this paper NEURAL NETWORK BASED CRYPTOGRAPHY. Under the section 3.1 it said: The aim is to improve the randomness of the random numbers generated by any algorithm using an NN. In ...
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Derivating random numbers from random numbers

If I have a "truly random number" $K$ of $L$ bits (whatever "truly random" means... is it a value from a normal distribution a truly random number, or only uniform distributions ...
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Are there on-line ways to use a block cipher to generate unique $n$ bits that guarantee collision-freeness for $2^n$ times?

$n$ is a run-time variable chosen each time the user runs the implementation. One way I can think is to use any block cipher, say AES, as a seeded CSPRNG to randomly shuffle list of numbers $0, 1, \...
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Does grouping password characters for readability decrease entropy?

For example, for a randomly generated password of 28 lowercase letters, which is about 128 bits of entropy, how would adding a space after every four characters affect it? ...
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Cryptographic Random Beacon VS Random Oracle

Let's start with what I mean by cryptographic random beacon (RB). A RB is a protocol among some parties who generate a random value all together such that: these parties do not trust each other the ...
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A source of randomness that anyone can independently, conveniently and robustly access?

Does there exist a source of randomness that anyone in the world can independently, conveniently and robustly access? For example, the 10th decimal place of the temperature in Mexico City is ...
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Random sampling vs incrementing randomness in cryptographic protocols

As an example to my question, I post the ECDSA signing algorithm for reference (from wikipedia) to sign a message $m$: Calculate $e = H ( m )$. Select a random integer $k \in [ 1 , n − 1 ] $ ...
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What are the fastest algorithms that sample from the uniform distribution?

Lots of cryptography algorithms rely on pseudorandom number generators. Sometimes, given a plaintext, you need to generate a pseudorandom number from it. What are some fast algorithms that do so? I've ...
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Sentinel ("trick") values for lattice attack on DSA with biased k (MSB)

I'm studying lattice attack using this sage script. There are 2 options in script: LSB and MSB. The most interesting option for me is MSB. It recovers private key with less then 100 signatures ...
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Weakness of XORing random bytes with secret key

Side A generates 16 (high quality) random bytes and performs XOR with a 16-byte secret key, then data transfers to side B, where the same secret key is used to recover the original 16 random bytes. Is ...
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How to generate a random string in Python for a mission-critical application

I'm trying to figure something out, but it is difficult for me. I need to generate a fully random string in Python. My current function is attached below. I just want to know whether this is secure ...
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209 views

Randomness extraction from a Santha-Vazirani (semi-random) source

In a quest to better understand randomness extractors (in the context of TRNG post-processing), I read some papers about the von Neumann Extractor and Santha-Vazirani (SV-) sources. The von Neumann ...
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Use of scrambler LFSR for randomness extraction of semi-random source

I am using a linear feedback shift register (LFSR) in a scrambler configuration as a randomness extractor for a weakly random source. This source is semi-random (aka. Santha-Vazirani source): the bits ...
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Is generalized birthday attack only suitable for the problem with multiple solutions?

In David Wagner's article A Generalized Birthday Problem, he said and I quote: Our algorithm works only when one can extend the size of the lists freely, i.e, in the special case where there are ...
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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 $a$, $b$, $...
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Does this paper find cryptographic weakness of SHA-256?

I found only the abstract and tables of this paper https://dl.acm.org/doi/abs/10.1145/3409501.3409513 From the abstract In this paper, the researchers proved that the modified SHA256 is viable to ...
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243 views

Why does the NIST Runs Test include a Frequency Test?

In the NIST suite of RNG tests (https://csrc.nist.gov/publications/detail/sp/800-22/rev-1a/final), one of the tests is the Runs Test, which tests counts of runs of 1's and 0's. According to the ...
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Is a LFSR sufficient for post-processing a biased TRNG?

I am building a TRNG on a FPGA based on ring oscillators. I found out that Linear Feedback Shift Registers (LFSRs) are commonly used for the post-processing of TRNGs. Here is my initial design: Let's ...
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Cryptographically correct way to roll a giveaway winner

I'm looking to create a fair selection of a giveaway winner, but I am versed enough in cryptography theory to determine if the below would hold up to public scrutiny if published on github. The reason ...
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Is it safe to say that a XOR with an unknown input provides a random output?

I am wondering if you have an input $x_{1}$ and you XOR it with an unknown random second input $x_{2}$, is it safe to say that the resulting $x_{1}\oplus x_{2}$ will be random ? The final idea would ...
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Why are $\lceil 1/\operatorname{entropy-per-bit} \rceil$ number of bits not sufficient to generate an unbiased bit?

Consider a biased RNG badrand() generating 1 with probability $0.9$ and 0 with probability $...
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On randomness related terminology clarification

It was suggested to provide a new question in the comments in How to combine $n$ 'less random' bits to generate one 'more random' bit?. Why there is no unbiased randomness (seeking ...
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Test the randomness of a random permutations, that was generated without Fisher-Yates?

Overview of the problem Before this gets immediately flagged as duplicate, I'm not interested in testing the Fisher-Yates shuffle for randomness, since this can simply be done by testing the ...
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What is the NIST recommended maximum bias for random number generators?

What is the maximum bias recommended by NIST for random number generators? This answer says that it is $2^{-64}$. Is it same for all applications? Does NIST have a publication with more information? I ...
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How to combine $n$ 'less random' bits to generate one 'more random' bit?

Suppose we have a random number generator badrand() generating 1 with probability $0.9$ and 0...
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Is there any standard present to measure strength of a generated key using true random number generator?

I was wondering how to measure the security strength of a generated secret key for the below protocol: "A 128 bit random number is generated by TRNG and the random number will be used as a ...
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How to ensure that a cryptographic implementation is reasonably sound/robust?

I know from the bottom of my heart how bad the idea of custom-crypto is. I absolutely concur with the recommendation that it should only be done by professionals who specialize in implementing crypto ...
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Any famous approach for analyzing the randomness of data?

I'm writing a function that will allow me to analyze the randomness of some input data and return some stats about the probability of this data to be random. Obviously it should be based on two things:...
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Soundness of Trevisan’s Extractor Against Quantum Side Information

I wonder how sound Trevisan's extractor can be against quantum side information. I checked many papers. And all of these papers were aiming to explain how sound Trevisan's Extractor is against quantum ...
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How to get ramdom number between 1 and 2048 from /dev/hwrng?

I am (perhaps naively) evaluating the security considerations of using the following code to create BIP39 seed phrases (on a read-only and offline Raspberry Pi). Apparently, using ...
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How big does M need to be in Blum Blum Shub?

I've read that Blum Blum Shub is a CSPRNG, defined by x_n+1 = x_n^2 mod M. I didn't understand that, and couldn't find any sources on how big should M be. Are 32 ...
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Recommendation of lightweight RNG for Miller-Rabin primality test

Miller-Rabin tests the compositeness of candidate numbers (hence, input $x$) that's often used as a primality test. The M-R test requires different random numbers for accuracy and confidence in the ...
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Can disjoint distributions be Computationally indistinguishable?

As mentioned in these notes definition 2 We say that $\{Xn\}_n$ and $\{Yn\}_n$ are computationally indistinguishable if, for all $\mathsf{nuPPT}$ $D$, there exists a negligible function $ε$ such that ...
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Why do some people believe that humans are "bad at" generating random numbers/characters like this?

I'm not even sure if they are serious, but I've heard many times that some people refuse to not only trust their computer to generate a random string (which is understandable) but also don't trust ...
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How does a pseudorandom generator produce a similar distribution to $U_{n}$?

According to Wikipedia, a function ${\displaystyle G:\{0,1\}^{\ell }\to \{0,1\}^{n}}$ with ${\displaystyle \ell < n}$ is a pseudorandom generator against $\mathcal {A}$ with bias $\epsilon$ if, ...
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Nth term for Linear Congruence Generators

We can get the N+1th term for a Linear Congruence Generator like this: x[n+1] = A * x[n] (mod m) by raising the A to the exponent of n like this: ...

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