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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How to validate the randomness of ECDSA signature generated using HSM?

I need to programmatically(using Python) validate whether the signature generated by using HSM RnG is actually random. Didn't found much content online, hence any help would be appreciated !!
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Why does the Fiat-Shamir heuristic not work without a random oracle?

Consider the following three stage interactive zero knowledge proof in round $i$ The prover sends some commitment $a_i$ to the verifier. The verifier picks a challenge $c_i\in \{0 ,1\}$ Depending on ...
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Is a number generator based on hashing an incremental string considered random?

Consider the following system 1 - fixed string as a seed, example "something" 2 - concat an increment number "something-1" 3 - hash it, assume it is "9f2054ea4d2c" 4 - take the first 3 digits to ...
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Is it possible to calculate the random factor r from a encrypted message and the private key in a paillier cryptosystem?

I have already done my research and found various sources that state that it is possible but there are also a lot of them that says it is not possible to recover $r$, this for example even states the ...
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Why does mt19937 fail the universal test in NIST SP 800-22?

Update: with the help of @SqueamishOssifrage and @PaulUzdak, we discovered that my NIST SP 800-22 has a broken universal test. So this becomes a moot question. Check this report. It seems to sail ...
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An alternative for /dev/urandom [migrated]

I like to overwrite my harddisk with random data. Since /dev/urandom as source is too slow to overwrite a large amount of data in a reasonable time, I'm looking for a good alternative. These two ...
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How can we reduce indistinguishability-from-random to other security notions?

In probabilistic encryption schemes, different notions of security exists. I'm interested in the relationship between two notions. One is the indistinguishability-from-random notion of security and ...
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Benefits of signing a random number [migrated]

Is there any benefit to signing a random number? e.g. a link for password reset, sent to email, often includes a base64 encoded random number to prevent someone guessing what the password reset link ...
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What is a popular entropy source for seeding a CSPRNG, which is actually weak and unreliable? [closed]

Say I want to seed a CSPRNG. What sources are popular, but unreliable? What sources should I even use?
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What is the most secure/reliable CSPRNG currently available? [closed]

In terms of period length, uniformity/distribution, what is the most secure/reliable CSPRNG currently available?
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What is the practical impact of using System.Random which is not cryptographically random?

I recently noticed a .NET software using PBKDF to derive an encryption key from a password string. This password string was ...
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Efficient way of generating a random number of N (less than 64) bits with exactly M bits equal to one [closed]

Would there be an efficient way to implement a function with the following signature: unsigned long long int random_word(size_t n, size_t m) that would generate ...
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Randomness Testing of Cryptographic Algorithim

I am new to algorithim randomness and confused at I guess a basic level question. Is it common for any cryptographic algorithim to have repetitions in its output i.e.let say 34 and D8 are two ...
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Statistical Analysis of Cryptographic Hashing Algorithms

I was wondering how can I use NIST Statistical Test Suite to check for the randomness of output generated by a cryptographic hashing algorithm, let say SHA-256? To be specific, how will I generate ...
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If an algorithm can not produce a true random stream, then an algorithm can not alter its entropy [closed]

Can a transform lower the Kolmogorov entropy of a true random stream and then restore that stream with out loss. If not true then this means a transform can not raise or lower the entropy.
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How can the 'randomness' of a finite sample of binary keys from a finite key space be estimated?

Given a set of bit sequences generated by an extractor, what would be a valid setting for estimating the randomness of these generated keys and what resolutions can be drawn for that extractor in ...
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Interpretation of certain results of NIST Test Suite

I am using NIST Test suite on a PRNG and have a confusion regarding some specific results. Following is the part of the results: ...
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AIS31 Software and Documentation

I have learned that there are two main test suitcase for randomness (reference): AIS 31 - German Federal Office for Information Security (BSI) SP 800-90B - U.S. National Institute for Standards and ...
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How does bit-wise operation work for encrypting grayscale images? [closed]

How does bit-wise operation work for encrypting grayscale images? In my Khan Academy course they encrypt an image with bitwise_and, ...
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What is the proof that a hash output contains random binary numbers

I have heard quotes by many that a SHA-512 hash output is random. Does anyone know what method was used to come to this conclusion? If it is not randomized, how could that be shown?
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NIST random excursion results

NIST specifies so-called random excursions test and random excursions variant test. From the description I can derive that the number of p-values should be 8 in the first case and 18 in the second. ...
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Can future Bitcoin hashes be considered a good source to generate random numbers?

There are a lot of miners trying to calculate the next valid SHA-256 hash using random strings, so can I consider that generated hashes have good randomness? How can I prove it? For example, use the ...
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Randomness Testing

Let say I have three sequences: S1 = {1,2,3,4,5,6,7,8,9,10} S2 = {3,7,1,9,4,10,5,8,6,2} S3 = {8,3,10,2,6,7,1,5,9,4} i.e. S2 and S3 are just the permutations of S1. Is there any method to check how ...
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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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Can randomness protect a list of signatures against forgery attacks?

Suppose we have a list of signatures $S = [s_1, .., s_n]$ for a list of messages $M = [m_1, .., m_n]$, and we want to verify that $S$ is a valid signature of $M$, so each $s_i$ should be valid for ...
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What information does $g^x$ reveal about $x$?

Let $p$ be a large prime number. Let $G$ be a subgroup of $\mathbb{Z}_p^*$ with order $q$ - again a large prime. Let $g$ be a generator of $G$. Consider the following standard protocol for ...
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Verifying randomness and uniqueness of TRNG output

We need to verify two claims about a set of numbers: They are random They are unique in the set (the set is about 200 billion (2TB bin storage)) Supposedly, the numbers were generated by a TRNG (...
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Can a deck of cards be used as a practical source of cryptographic randomness?

This is not a duplicate of Entropy measurement from shuffled cards, as this concerns use of cards as a cryptographic entropy source, rather than calculating entropy from some number of cards. The ...
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How to test for randomness using FIPS 140-2 [closed]

I designed a PRBG which produced 20000 bits. Please help me here. How do I test for randomness using FIPS 140-2 suit. I know what each test entails. Question is, can I get like a program/software/code ...
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Does encoding a secret affect security?

My question is simple. I have a secret that is generated with a 10 byte long pseudorandom generator library (e.g. Java's SecureRandom), that in theory provides a security equivalent to $2^{40}$ (...
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Von Neumann Extractor - Which bit is retained?

Which bit is retained in the Von Neumann debiasing algorithm? 00 and 11 are discarded and 10, 01 are retained but is the first or the second bit retained or does it matter? In other words: first: ...
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ECDSA signature of a random 32 byte number vs. the hash of the number

I'm working on an application that involves signing a 32 byte random number generated by the OS. Assuming the RNG works as intended, is it safe to sign the random number itself rather than a hash of ...
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Origin of the Chi-Squared test statistic for serial test (two bit test)

On page 181 of Handbook of Applied Cryptography Chapter Five, it states the following: The purpose of this test is to determine whether the number of occurrences of 00, 01, 10, and 11 as ...
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Where can I find some thought-provoking questions on the fundamentals of Cryptography? [closed]

The question might sound broad, allow me to explain. Cryptography is a diverse domain. I have been in Crypto research since last four years. Recently, one of my colleague got interviewed by an IT ...
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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 $...
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Random letter swap soloution

I am working on a way to decipher some text generated by a small piece of code (see below). This piece of code swaps letters in the sentence at random and was wondering if there where any techniques ...
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Security of (2,2) Shamir's visual secret sharing scheme : How are the 2 shares random?

From the Visual Cryptography by Shamir and Noar. Let us take the pixel expansion as 2. Therefore, each pixel will be represented by 2 pixels (also called as subpixels) in a share. Since this is a (2,...
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How did I get a nonuniform distribution of UUID4s across MD5 space?

We have a system that processes data. Each entity has an ID that is generated using uuid4() in Python. Later, that ID is used as a partition key for AWS Kinesis. ...
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Brute forcing/hacking Secure passphrases - difficulty for random strings vs real words

I was wondering about this topic of brute forcing passwords,or ANY other way to deriving them - and asking myself whats more secure (relatively): A Password which includes A) 30 digits length- a ...
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Low entropy - how does it compromise the crypto

One of the often pointed out mistake in dealing with crypto is not having enough entropy in the system. Without enough entropy the random numbers generated are not random enough. But what I am not ...
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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 ...
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Is there any bias whatsoever in modern hash function outputs?

The following is a representative example of a common hash function:- The asymmetry is clear, and I would expect additional edge effects in the A and E output words. So I'd be surprised if the ...
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Golomb's Randomness postulates

In Handbook of applied cryptography, Golomb's randomness postulates are given: Let $s$ be a periodic sequence of period $N$. Golomb’s randomness postulates are the following. R1: In the cycle $s_N$ ...
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Method for generating random number(s) [closed]

I was reading about random numbers and their usage in security. I'd like to verify with more experienced people how good this method of generating random numbers will be. Human beings are very hard ...
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Example of cryptography random number

I read that random numbers are being used in cryptography and security. I think I have idea how to truly generate true random, non-deterministic number. But before continuing further I'd like to ask ...
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How to determine the fastest OpenSSL cryptographic algorithm

This question does have to do with cryptography, but not necessarily with encrypting meaningful data. This is my first post here, so if I'm going about this question incorrectly please let me know. ...
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Impact of a non-uniform distribution in a secret sharing scheme

When it comes to the secret sharing schemes, it seems that the random numbers need to be drawn uniformly. Is there any difference between the random numbers from uniform distribution and the non-...
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Using Tweets as a Random seed

I would like to start by saying I know nothing about Cryptography and was reading up on how to choose a random seed and this link is something that I found. What I basically understood that the seed ...
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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 ...
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Implementing randomness extractors

A randomness extractor is a function that takes an input sampled from high entropy distribution and outputs a value that is close to uniform distribution. It is slightly different from a PRG. PRGs ...