Questions tagged [random-number-generator]
A random number generator is a software or hardware solution which functions as a generator of (real or pseudo) random numbers (or bits).
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How much entropy is lost via hashing when you add known or low entropy data?
(I updated the title, as I think there was some confusion as to the question)
Here's the question:
For example, if I have a bit stream that is 64K bytes long and there is about 16 *8 bits worth of ...
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How broken is a xor of two LCGs?
Suppose we define a PRG as the xor of two LCGs modulo a 64-bit prime: something like the following Python code.
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Using a Hash as a secure PRNG
I was just looking at some NIST PRNG recommendations, specifically at Hash_DRBG. I read briefly through the algorithm, and even though it is not overly complex, it still seems unnecessary to me. I ...
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Cryptographic security of PHP mt_rand() function using Mersenne Twister algo
At StackOverflow, this question has been asked. It uses additional random entropy and a hash method (among others) to try and create a cryptographically secure pseudo-random number generator for PHP. ...
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Dice vs quantum random number generator
I recently championed quantum key distribution networks. This has led me to also question quantum random number generators. It appears that randomness is randomness, even if made by custom quantum ...
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How vulnerable is the C rand() in public cryptography protocols?
I just learned about the basics of public cryptography a few weeks ago and I am curious as to why the C rand() function should not be used for crypto schemes. For example, say I want to generate a ...
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Technical details of attack on Android bitcoin usage of SecureRandom
Reports are surfacing that Android's Java SecureRandom class has issues and isn't totally secure.
A specific example of how this issue translates to applications is bitcoin, where reports are stating ...
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Radioactive Decay, Gaussian or Uniform?
I'm trying to understand the nature of true randomness. I'm building an RNG using a radioactive source. Basically, I'm measuring the time between consecutive decays which in theory should be ...
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How to evaluate chi squared result?
I've been recently working on a (supposedly) TRNG. I'm still at the beginning of the project, so it is certainly not cryptographically secure yet, for now I'm just playing around. In fact, I've ...
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Initialize a PRNG with a password
Let's assume that we have a secure PRNG. Is it "safe" to initialize it with password, or seed based on a password like SHA256(password)?
If yes, is it "safe" to generate an RSA or DSA key from it?
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How does generating random numbers "remove entropy from your system"?
In a previous question, I quoted the --gen-random entry in the GPG Man Pages. At the end it says:
PLEASE, don’t use this command unless you know what you are ...
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Usage difference between x86 RDRAND and RDSEED
Modern x86 CPUs often have the RDRAND and RDSEED instructions for hardware generation of random numbers. I just don't understand the difference between them.
Intel has this document: https://...
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Definition of a CSPRNG
I am interested in what conditions are necessary and sufficient to define a cryptographically secure pseudo-random number generator (CSPRNG).
Wikipedia lists two defining characteristics:
It ...
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Correct way to map random number to defined range?
Say that we have a secure random number generation that outputs 32 bit random numbers, so it's output is a true random number between 0 and a MAX.
What is the best way to map this random number to a ...
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What are the methods to construct a primitive binary nonlinear feedback shift register (NLFSR)?
Given a binary shift register of $n$ bits, a primitive binary nonlinear feedback shift register will generate a sequence with a period of $2^n - 1$.
While I am unable to find a paper which directly ...
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How to tell if a hardware RNG is rigged?
On a related note of building my own RNG, as someone suggested to use several commericial solutions how can I check if it is rigged against me? (although I am still strongly biased to a homebrew ...
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Shared secret: Generating Random Permutation
-- or: How to Play Poker Without a Dealer
I know this question is long but it's a really interesting theoretical problem about shared secrets and multi-party computation.
General Problem: "Shared ...
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What level of security is provided when a Feistel Cipher is used as a round function of another Feistel Cipher?
Recently, I was reading: Are there any specific requirements for the function F in a Feistel cipher?, and the answer posted mentions a Feistel Cipher named Turtle, which uses a four-round Feistel ...
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How to generate a list of unique random strings?
How would you generate a list of distinct random strings, where all strings are alphanumeric and have a fixed length?
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Is a die implemented in a physics engine truly random?
So, a fair die throw is really random, not pseudo. So, would a RNG implemented as the result of a die throw in a physics engine (say, Newton, Havok, Nvidia's PhysX) be regarded as both ...
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Estimating bits of entropy
I know there are different statistical tests out there (NIST, Dieharder, etc), which all do different ways of analyzing entropy.
What I'm having a hard time finding is any particular literature ...
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If I am about to generate one-time pad, where should I generate my pads from?
If I want to generate a few one-time pads, is it OK to just read required number of bytes from /dev/urandom without weakening information-theoretical security?
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Does an encrypted random sequence conserve its "randomness"?
If you have a random uniform sequence of bits $A$ generated by a TRNG with good performance of randomness tests (eg Dieharder, NIST, Kolmogorov complexity, chi-square, etc) and perform an encryption (...
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Predicting PRNG given some of its previous output
I a have a question about PRNGs and this is my very first experience with them. I have the following generator that takes a 56-bit seed $p$ during initialization and then chooses both $X$ and $Y$ ...
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Does Microsoft use Dual_EC_DRBG by default?
So, as we all know, Dual_EC_DRBG contains an NSA back door. At this point, there is no reason to call it a "potential" or even an "alleged" back door; the presence is obvious even to the NY Times.
As ...
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Perfect shuffle possible with limited raw entropy?
I am trying to shuffle a standard 52-card deck in a perfect way (every outcome should be possible at an equal chance). I am not, at this point, concerned with cryptanalysis attacks against it.
I have ...
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Does chaining random number generators lead to loss of randomness?
Assume you chain random number generators, i.e use the result of one PRNG as the seed for the next. What kind of errors can that introduce in the randomness of the numbers generated?
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Can reduced-round ChaCha be used as non-cryptographic fast PRNG to produce output indistinguishable from random data?
The fastest known attack against the Salsa20 family of stream ciphers requires 2137 simple operations against Salsa20/7, or 2244 against Salsa20/8. The 8-round version encrypts data at 1.88 cycles-per-...
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Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
I am actually looking for available crypto libraries including a deterministic random generator for the purpose of a dedicated crypto key generator unit.
I have a simple question about the X9.31 based ...
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Good entropy source for generating openssl keys
I need to generate a CA (4096-bit RSA) and server keys for openvpn and I want them to be "top quality". Here is my plan:
gather entropy from multiple sources (saving individual files): FreeBSD Yarrow,...
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How distinct are the meanings of the terms "CSPRNG," "DRBG" and "stream cipher"?
Are there universal, consensus definitions for the following terms?
Cryptographically secure pseudo-random number generator ("CSPRNG")
Deterministic random bit generator ("DRBG")
Stream cipher
This ...
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Distributed generation of random numbers
I have a network of $N \gg 1$ nodes. Some relatively low fraction $p$ (e.g., $p \simeq 0.01$) of them is under the control of a malicious attacker. Nodes can talk to each others and verify each other'...
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What should be used as a source for entropy?
I have hardware-based RNG which consists of TRNG and PRNG. TRNG is giving out a 512-bit number which is being used as a seed for PRNG. RNG is generating a 160-bit random number using PRNG and ...
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Is it possible to determine or estimate the period for Blum-Micali PRG?
The Blum-Micali is a cryptographically secure pseudorandom number generator.
The construction (from wikipedia):
Let $p$ be an odd prime, and let $g$ be a primitive root modulo $p$.
Let $x_0$ be a ...
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How feasible would it be to generate 300 million public key pairs in 8 hours?
Assume there is a hypothetical situation where one would need to generate hundreds of millions of public key pairs of reasonable strength in a limited time.
What would be required in terms of ...
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Why does BCRYPT_RNG_DUAL_EC_ALGORITHM get removed from CNG API on Windows 10?
On article at => Microsoft Docs
CNG Algorithm Identifiers
I notice that BCRYPT_RNG_DUAL_EC_ALGORITHM is now removed since Windows 10.
Beginning with Windows ...
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HRNG for One Time Pad
I have just advanced to the last grade of high school (in Denmark). In this year, we all get to do one big project, where we can build/invent/create whatever we want to "solve a problem". As I study ...
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Is there some way to generate a non-predictable random number in a decentralised network?
Is there a way to generate a random number with given restrictions:
It will be used in a decentralised network with a big number of peers (no central authority to generate it)
Its generation should ...
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Extracting randomness from highly-biased RNG
I have a source with a very low entropy (like 3 entropy bits per 1024 source bits). But I need to construct a 128 bit seed from the source.
Will it be helpful to XOR 350 bits with jump 128 bits, e.g....
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Generating Random Primes
Although this has been extensively discussed around here, I'm curious whether my approach makes sense, or I should just stick to "the standard version".
I'm implementing some homomorphic encryption ...
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Trial divisions before Miller-Rabin checks?
I'm trying to understand prime number generation (more correctly, the primality checking) as described in Handbook of Applied Cryptography.
The context is circa pages 145 - 150, and specifically ...
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"Seed" vs "seed key"
The FIPS 140-2 Derived Test Requirements has a statement:
AS07.09: (Levels 1, 2, 3, and 4) The seed and seed key shall not have the same value.
What is the difference between a seed and a "seed ...
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Introduction to LLL algorithm applied to linear modular inequalities
What is the Lenstra–Lenstra–Lovász lattice basis reduction algorithm about?
How is it applied to solve for $x\pmod m$ a system of modular inequalities $(u_i\,x+v_i\bmod m)<w$ for $0\le i<n$?
I'm ...
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Is SHA-1 secure when used to implement a PRNG
I read SHA-1 is still a secured hashing function with no collision found as of now. However, it's just a matter of time for someone to come up with such a collision or attack. Therefore, in new ...
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LFSR get output from characteristic polynomial?
Say you have a characteristic polynomial of an LFSR:
$$f(X) = X^4 + X^3 + 1$$
How can I use this function f to get the output of the LFSR, given some initial state?
Obviously I can create the LFSR ...
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Deterministically combine more than one source of entropy
What is the proper/canonical way to do this?
For example, $0 < r1 < 1$ and $0 < r2 < 1$. Presuming uniformly distributed probabilities for the two, combining/averaging them is going to ...
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Algorithm: How to use x and y mouse movement co-ordinates to generate random data?
Background:
I'm making a program for fun as a learning exercise. I want to generate some actual random key material (not pseudorandom) from a JavaScript program. For my program is just for encrypting/...
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How to find generator $g$ in a cyclic group?
As generator $g$ is used in DH how do you find a combination of prime $p$ and $g$? eg: if we choose $p=23$ and its generator is $7$ (given in the book) how do we find the generator?
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RFC6979: error in reference implementation?
If I correctly understand RFC 6979, there is an error in the ref implementation section 3.2.
In the step H2, RFC specification says
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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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