Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [randomness]

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

0
votes
3answers
57 views

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 ...
1
vote
0answers
67 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 ...
0
votes
1answer
25 views

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 ...
3
votes
1answer
170 views

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 ...
3
votes
2answers
139 views

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 (...
4
votes
3answers
196 views

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 ...
-1
votes
2answers
75 views

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 ...
0
votes
1answer
62 views

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 $2^{40}$ (...
3
votes
1answer
145 views

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: ...
1
vote
1answer
60 views

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 ...
1
vote
1answer
44 views

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 ...
-2
votes
1answer
88 views

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 ...
0
votes
0answers
41 views

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 $...
-1
votes
1answer
50 views

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 ...
1
vote
1answer
90 views

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,...
7
votes
1answer
177 views

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. ...
-1
votes
1answer
60 views

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 ...
2
votes
3answers
166 views

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 ...
2
votes
2answers
265 views

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 ...
0
votes
1answer
148 views

Is there any bias whatsoever in modern hash function outputs?

We know that the output bias of a randomness extractor is $ \epsilon = 2^{-(sn-k)/2} $ from What is the relationship between entropy conditioning and final output bias in a TRNG?. The following is a ...
3
votes
1answer
176 views

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 $s_N$ ...
-2
votes
1answer
55 views

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 ...
3
votes
2answers
2k views

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 ...
1
vote
1answer
80 views

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. ...
2
votes
3answers
67 views

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-...
18
votes
4answers
4k views

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 ...
3
votes
5answers
245 views

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 ...
3
votes
2answers
180 views

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 ...
4
votes
3answers
3k views

Cryptography's random number problem?

Sophie Chen at Wired Magazine; quantum mechanics could solve cryptography's random number problem Such machine already exist, but it's too huge and not so fast in order to use it all the time. ...
1
vote
2answers
266 views

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 ...
4
votes
2answers
232 views

Does AES encrypting /dev/zero and feeding output to AES again increase entropy of the ciphertext?

I just thought about what would change if would pipe the output of ...
1
vote
1answer
49 views

Privacy of randomness using extractors and PRGs

The Wikipedia article on randomness extraction states that they are different to pseudo random number generators but the distinction is very hazy. Both seem to take in some input quasi-randomness and ...
3
votes
3answers
140 views

Is it correct to concatenate (pseudo-)random byte values before testing them with the NIST suite or tools like dieharder?

Let's assume I have thousands of (pseudo-)random 4-byte values. The values are 4 byte random values which a blackbox device gave me. I got these values by requesting them. In between others might have ...
3
votes
1answer
92 views

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 ...
2
votes
1answer
69 views

Does this description of verifiable random functions seem accurate?

I've been thinking about verifiable random functions recently due to my interest in sortition (random selection of political officials). I wrote up this little paragraph below, and I'm wondering: Does ...
15
votes
2answers
2k views

What is the difference between TRNG and CSPRNG?

I understand the output of a TRNG is almost impossible to reproduce, such a flipping a coin 100 times to produce a 100-bit sequence. However, it is also my understanding that a CSPRNG produces an ...
4
votes
0answers
87 views

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 ...
-2
votes
1answer
175 views

Using IPv6 as seed + time almost as good as TRNG? [closed]

I just figured out a way to create a RNG that may be almost as good as TRNG (true random number generator) and need some input to confirm/clarify. What if I use the IPv6 address of a visitor as a ...
2
votes
1answer
171 views

Problems understanding the applications of pseudo random number generators

I am trying to explore different methods used to generate pseudo-random numbers for my project in maths and I would be very grateful for some help or references to valuable sources as it is very hard ...
2
votes
1answer
96 views

Some considerations about PRNGs

Recently I read about pseudorandom generators and I have some observations: My conlusion is a such that a secure implementation of a PRNG had to be blocking or returning an error code when it is too ...
1
vote
1answer
87 views

Pseudo-random generators and pitfalls

I've read the Chapter "Randomness" from the Serious Cryptography book and it raised some questions. Namely: It is written that Mersenne Twister is proved to be cryptographically irreliable. And that ...
19
votes
5answers
2k views

How many hex digits do I need to compare when manually checking hash functions?

I sometimes run sha256sum on large files after transferring them from one place to another, and will just skim the hash output to verify it's correct. But, I usually just look at the first/last 5 or 6 ...
2
votes
1answer
93 views

adaptation of NIST sp800-22 for short sequences

I would like to ask about the NIST test suite for randomness evaluation. The test suite consists of 15 subtests which evaluate the particular property of the sequence. In fact, each test has an ...
4
votes
1answer
89 views

Sequence test for an image cipher

I am reading a paper on security analysis of a cipher image using the paper at the following URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8306512&tag=1 It indicates some ...
1
vote
1answer
113 views

repeatedly hashing result and using reverse sequence as RNG secure?

I want to have a source of randomness for which: no one but me can predict the next number in the sequence. I know the entire sequence in advance, but I have no way of manipulating it once the first ...
1
vote
1answer
115 views

LFS Kolmogorov Randomness

Consider following LFS register (where + denotes addition modulo 2) I have found the output sequence as 1,0,1,1. I know that The K(s) of a string s is defined as the length of the shortest computer ...
0
votes
1answer
83 views

Expected Linear Complexity of a sequence

Let (s) be a sequence of length n. What are the expected linear complexities of (s) and $(s)^{\infty}$ (meaning that the periodic version of s)? I have no idea of the answer to this question? What ...
0
votes
1answer
249 views

Dieharder input data format. Do I need new line at the end?

I am testing my sequence for randomness using Dieharder with a command like dieharder -a -g 202 -f in.txt >>result.txt my in.txt looks like ...
2
votes
1answer
98 views

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 ...
4
votes
1answer
121 views

Synthetic Jitter to Combat Timing Attacks

We are working on some tooling. It has a networking kernel. We would like to think that jitter built into the kernel would help with timing attacks? Is this true?