creation of (real or pseudo) random numbers (or bits).

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2answers
490 views

Is any decent RNG acceptable as a stream cipher?

I have a function f(x,n) that takes a 128-bit key x, and generates n bytes of pseudo-random data. I've tested the output bytes this function for various keys with the NIST RNG testing suite (NIST ...
4
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2answers
374 views

Feedback on rolling my own entropy gatherer

First of all, I don't recommend doing this. This was something I created when I didn't know better and didn't have a solution available to me. Long ago I created my own entropy gather for a ...
4
votes
2answers
824 views

Is it secure to concatenate two 16-bit random numbers into a 32-bit one?

I'm working on a security application for RF modules aimed to protect a communication between an autarkic sensor and a line-powered receiver against MITM (man-in-the-middle attacks). I decided to use ...
4
votes
1answer
714 views

Is it feasible to break Diffie-Hellman key exchange when the implementation uses a poor-quality PRNG?

I've come across an implementation of DH in Java that uses the Random class to generate the secret integer value $a$, as shown in in Wikipedia's description of the ...
4
votes
1answer
526 views

How secure is my OTP program?

I'm writing an One-Time Pad encryption program, because I got really interested in the idea of " encryption which has been proven to be impossible to crack if used correctly". I'm writing the program ...
4
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2answers
2k views

Randomness test question from FIPS 140-1 and comparison with 140-2

In FIPS 140-1 there are 4 statistical random number generator tests (The Monobit Test, The Poker Test, The Runs Test and The Long Runs Test. Then FIPS 140-2 came along and supposedly tightened the ...
4
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1answer
799 views

Correctly generating cryptographically secure pseudorandom numbers (in C)?

I am learning about cryptography, purely for my own interest. As part of that, I am implementing a simple one-time-pad toolset in C. Naturally, I need to generate random numbers to create the pad, ...
4
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1answer
36 views

Generate a random number $r \in \{1,2, \dots , k\}$, where $k$ is not public and is distributedly held

A set of parties can securely generate a random number $r \in \{1,2,3,\dots, k\}$ when $k$ is publicly known. However, can we generate the random number $r$ if $k$ is not publicly known and is held by ...
4
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2answers
96 views

Is the RC4 keystream random or not?

I have cause to use the PRNG half of RC4, but am seriously confused as to the randomness of its output. (Only the PRNG half.) On the one hand, there is a large body of literature finding ever ...
4
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5answers
171 views

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 ...
4
votes
1answer
141 views

Generating unsigned, bounded random value using signed bounded random values

Use case: I have a random number generator that can generate random numbers in a range that is limited by a number $x$, say $x$ ranges from $2$ to $2^{(n - 1)} - 1$ exclusive. In this case $n$ is ...
4
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1answer
107 views

What is an impure NIST true random number generator?

I'm working on a true random number generator, and I came across this phrase in the American NIST guide, in section 6.4.1 Non-Approved Conditioning Components: The entropy rate provided shall be ...
4
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1answer
652 views

True Random Number Generator by milliseconds per keystroke (TRNG-Kms)

The simplest way to generate truly random numbers for OTP keys is to measure the time in milliseconds between each keystroke on a keyboard. The randomness depends on the user typing in various speeds. ...
4
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2answers
459 views

Can I combine two PRNGs to make use of more seed data?

I have 320 bits of seed data (actually 512 bits of data with 320 bits of entropy, derived from a Diffie-Hellman shared secret and nonces). The PRNG I am using at the moment is the android version of ...
4
votes
1answer
93 views

What problems with “random” data would cause this result from Ent?

I'm playing around with a novel kind of source of "random" data and Ent is currently giving me results like this: Entropy = 7.977080 bits per byte. Optimum compression would reduce the size of this ...
4
votes
1answer
82 views

How to convert AES to a PRNG in order to run NIST Statistical Test Suite?

I want to run statistical tests on my implementation of AES. How should I convert it into a PRNG? Is there a standard way to go about doing this? I could not find much information about this although ...
4
votes
2answers
97 views

A periodic PRNG based on hash function?

I need a PRNG which provides 128 bytes numbers. Let's say that given a symmetric key $K$ and an internal state $s$ I use the PRF HMAC-SHA512 this way: The output is PRNG($K, s$) = ...
4
votes
3answers
115 views

How does the birthday paradox apply to random keys?

I'm developing a web app where I wish to use pseudorandom keys for items, perhaps akin to Imgur. I was thinking about how many combinations I need to reduce the chance of someone guessing any random ...
4
votes
1answer
166 views

Can a PRNG with a fixed amount of entropy always be detected?

Given a fixed seed (i.e. no ongoing source on entropy), is there (practically or theoretically) any PRNG algorithm that can generate an infinite sequence of random numbers such that an observer cannot ...
4
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2answers
327 views

Advantages of combined PRNGs

This question is related to this one in intention, and this one in scope. Would I be guarding myself against future attacks on a single PRNG if I combine two (or more) together? I am thinking of ...
4
votes
3answers
391 views

Endless PRNG from PRNG with specific stretch?

Every definition of pseudorandom generator that I've seen says it takes n-bit strings and gives poly(n)-bit strings. Is there a proof that if there is such a pseudorandom generator then there is a ...
4
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1answer
1k views

Are there any Javascript CSPRNGs? [closed]

I'm writing some software that requires the use of a CSPRNG with javascript for use in the browser and I'm wondering what libraries are available. Crypto-js doesn't seem to have a CSPRNG I can ...
4
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1answer
80 views

How to design a deliberately weak PRNG for experimentation?

I'm looking for a PRNG that is deliberately weak, that is, follows a set of rules stochasticly. For example: Encounters a set of bits that is a multiple of X, starts exhibiting bias, or starts to ...
4
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1answer
169 views

Cryptographic random numbers for key generation

I am trying to understand how a cryptographic library works (for example, one that provides assymetric encryption such as RSA), but I'm running into a few problems about the key-generation. There are ...
4
votes
1answer
221 views

How does a backdoor in the RNG enable an attacker to break encryption protocols?

I'm wondering how a backdoor in a random-number generator (as rumored the NSA have placed), actually compromises the security of things like VPNs or TSL/SSL. What I understand is that, if such a ...
4
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1answer
2k views

Who uses the RSA BSAFE library? [duplicate]

Who uses RSA's BSAFE library? Does anyone know what products use it, or have any statistics on how many end users use something that is built on BSAFE? Background: BSAFE is one of the oldest ...
4
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0answers
70 views

Secure entropy extractor for thermal noise collected from camera input?

I have read this paper (pdf) which talks about measuring the entropy of thermal noise collected from camera input. They estimate the minimum entropy at about 4 bits per pixel. Probably estimating 1 ...
4
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0answers
49 views

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 ...
4
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2answers
197 views

Alternative sources of random numbers

Considering that algorithmic methods for generating unpredictable streams are hard to come by, I've wondered if any of these potential sources are good for making keys, seeds, and the like: stocks, ...
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votes
4answers
1k views

Which is more secure using a CSPRNG for a One-time pad, or AES?

In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
3
votes
2answers
156 views

CSPRNG that cannot be used as random extractor

Are there any specific CSPRNG's that cannot be used as randomness extractor within a TRNG? In other words, can you simply provide enough entropy gathered from a good entropy source as seed in any ...
3
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2answers
462 views

Map Bytes to Number

Using node.js crypto library I can generate cryptographically strong bytes. How can I use this to generate a random number between 0 and 9999 (both inclusive)?
3
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4answers
1k views

random number generator 10-side dice alternative

A lot of sites (e.g. Dirk Rijmenants') refer to 10-side dice to generate random number for one-time-pad. I was thinking about new ways to generate random numbers, letters and passwords. here what I ...
3
votes
2answers
289 views

How to generate a random integer in interval $[1, 2^n-1]$ from random integer in interval $[0, 2^n-1]$?

For a project I am working on, I have access to a CSPRNG that outputs a random integer in the interval $[0, 2^n-1]$ for any integer $n$ greater than 0. I cannot use the zero values, so I have my RNG ...
3
votes
2answers
948 views

Generating unbiased numbers with a biased six sided die?

Eve takes a fair six-sided die and adds some heavy paint to the side of the die with the 6 on it. This results in a biased die that rolls a 6 with probability 2/7, and each other number (1-5) with ...
3
votes
2answers
166 views

Physical entropy source: How many bits entropy per byte is sufficent?

8 bit / byte would be perfect obviously. head -c 1M /dev/urandom | ent gives ~ 7.9998 bits per byte. Now, if I have a physical entropy source, how much entropy ...
3
votes
1answer
464 views

What weaknesses in Hash_DRBG did NIST find and fix?

Matthew Green states in the Practical Kleptography presentation (video, at about 12:15) that Hash_DRBG (from SP800-90A) as originally proposed by NSA had potentially exploitable flaws or bugs and that ...
3
votes
1answer
609 views

Are there secure stream ciphers that cannot be parallelized?

Are there any stream ciphers (or a deterministic random number generators, that should work as well I guess?) that cannot be parallelized? So for example if I seed it with a specific value, and then ...
3
votes
1answer
588 views

Generating a cryptographically secure, many-time use, symmetric encryption key

I need to generate a 256 bit encryption key described by the adjectives in the title. Currently I intend to create the key using this RNG. Is this a secure manner of creating the key, given that it ...
3
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2answers
1k views

PRNG determinism (and java.security.SecureRandom)

Looking at getDefaultPRNG() in java.security.SecureRandom makes me very unsure about how to use it. On my desktop, it uses sun.security.provider.NativePRNG, which reads from ...
3
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2answers
495 views

Whitening and randomness extraction

The Von Neumann randomness extractor is explicitly mentioned in the randomness extractor page of Wikipedia, but strangely enough that page does not contain any reference to whitening the results of an ...
3
votes
1answer
1k views

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 ...
3
votes
1answer
386 views

Predicting Java's PRNG using partial output

I have a program (a game) that uses Java's nextInt function with parameter 0x10000 to get a random 16-bit number. Java's ...
3
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2answers
333 views

Breaking a PRNG Scheme

Assume the following scheme for a PRNG generating decimals in [0,100) Given a message and a key, compute tag := HMAC512(message, key). Take the first 5 hexadecimal characters of the tag. If the ...
3
votes
1answer
135 views

Potential vulnerability in DH key selection - am I understanding this right?

I'm reading through a DH implementation, and I think I found a potential hole. Public $p$ and $g$ values are properly selected. A candidate secret value $\bar a$ is pseudo-randomly selected such ...
3
votes
1answer
326 views

Conforming Randomness To An Alphabet

Imagine that we're trying to create a function to generate a random string conforming to a user-supplied alphabet. That way, users can generate random strings with given characters. Something like: ...
3
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2answers
129 views

Will entropy be lost by using a DRBG?

Lets assume we have a DRGB (deterministic random bit generator) which is seeded by a good true RBG (random bit generator). Before any bit has been read from the DRBG, the entropy is clearly the number ...
3
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1answer
131 views

CTR DRBG dependent on request size?

I am trying to understand the CTR DRBG specification in NIST SP 800-90A. It seems slightly different to a pure stream cipher in that the key and counter are reset after each generate call using the ...
3
votes
1answer
96 views

Is this JS library using openssl genrsa -rand improperly?

pem, a JS wrapper around openssl, has the following code in it: var params = ['genrsa', '-rand', '/var/log/mail:/var/log/messages', keyBitsize ]; Am ...
3
votes
3answers
387 views

How to roll my own hardware RNG?

I am considering building a hardware RNG myself using cheap parts. Is this a good idea and safe enough? Random sources: amplified Zener noise from one randomly chosen ...