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

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57
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10answers
4k views

Is modern encryption needlessly complicated?

RSA, DES, AES, etc. all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
34
votes
6answers
12k views

Who uses Dual_EC_DRBG?

Recent news articles have suggested that the NSA may be involved in trying to influence the cryptography in public standards or commercially deployed software, to enable the NSA to decrypt the ...
26
votes
1answer
24k views

Explaining weakness of Dual EC DRBG to wider audience?

I have an audience of senior (non-technical) executives and senior technical people who are taking the backdoor in Dual_EC_DRBG and considering it as a weakness of Elliptic curves in general. I can ...
18
votes
4answers
1k views

How to fairly select a random number for a game without trusting a third party?

Several people are playing a game with random events and require a way to produce a random number. (Such as dice rolls or a lottery.) Can this be done such that each player has the power to be ...
14
votes
2answers
1k views

Blum Blum Shub vs. AES-CTR or other CSPRNGs

Following on from D.W.'s comments on a previous question, what properties does Blum Blum Shub have that make it better / worse than other PRNGs? Are there significant implementation difficulties or ...
14
votes
5answers
2k views

Could RDRAND (Intel) compromise entropy?

I was recently discussing the issue of RDRAND in Intel chips and the whole issue about how NSA could potentially be influencing Intel to weaken or create backdoors in their design. This petition was ...
11
votes
1answer
485 views

Why did NIST remove The Lempel-Ziv Compression test from the Statistical Test Suite?

NIST removed "The Lempel-Ziv Compression" test from the Statistical Test Suite in revision 2008 and above and has not incorporated it since – see revision 2010. Why was it removed? Does it no longer ...
11
votes
1answer
1k views

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 ...
10
votes
4answers
913 views

Properties of PRNG / Hashes

There are a lot of quite elaborate PRNG's out there (e.g. Mersenne Twister et.al.), and they have some important properties, especially when it comes to crypto applications. So, I was wondering how ...
10
votes
1answer
405 views

How random are commercial TRNGS

I'm thinking about buying a USB TRNG. How do I evaluate its randomness? I'm sure some are better than others but which is which? Are thermal-noise better than radio-noise TRNGs?
9
votes
1answer
3k views

What to watch for with openssl generating weak keys? (low entropy)

(Disclaimer: I am regular software engineer with only basic crypto knowledge, so helpful if can be explained for a layman.) I am concerned about generating weak keys on a shared linux box with ...
9
votes
3answers
189 views

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?
9
votes
3answers
339 views

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. ...
8
votes
2answers
456 views

creating a small number from a cryptographically secure random string

i'm trying to figure out the best way to generate a cryptographically secure random number between 0 and 200 from a cryptographically random string of bytes (ie. read from /dev/urandom or some such) ...
8
votes
2answers
1k views

Is HMAC-DRBG or Hash-DRBG stronger?

Out of the two deterministic random bit generators defined in section 10.1 of NIST SP 800-90A (i.e. based on hash functions), which one is cryptographically stronger? Hash-DRBG (Section 10.1.1) ...
7
votes
3answers
723 views

What tests can I do to ensure my PRNG is working correctly?

In the past I have used the Chi-squared test to check the statistical randomness of my generator. Is this a good test to use? Are there other tests?
7
votes
3answers
553 views

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 $Y$ ...
7
votes
1answer
1k views

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 ...
7
votes
1answer
3k views

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. ...
7
votes
2answers
2k views

Predicting values from a Linear Congruential Generator

I have learnt that Linear Congruential Random Number Generators are not cryptographically secure - my understanding is that given an LCG of the form: ...
7
votes
1answer
726 views

What stops the Multiply-With-Carry Random Number Generator from being a Cryptographically Secure Pseudo-Random Number Generator?

Despite the fact that Marsaglia's MWC PRNG (multiply-with-carry random number generator) is considered to be "the mother of all RNGs", it does not seem to be considered to be a CSPRNG ...
7
votes
2answers
427 views

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 ...
7
votes
2answers
239 views

Testing the Fortuna random number generator?

I have implemented the Fortuna random number generator as described in chapter 10 of "Practical Cryptography" (Ferguson and Schneier, Wiley, 2003), the result can be found at ...
7
votes
2answers
463 views

Is FIPS 140-2's “Continuous random number generator test” practical?

Section 4.9.2 of FIPS PUB 140-2 specifies, amongst other things, a "Continuous random number generator test." Here are the relavant bits: If each call to a[n] RNG produces blocks of n bits ...
6
votes
3answers
2k views

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?
6
votes
3answers
413 views

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? ...
6
votes
2answers
921 views

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 ...
6
votes
2answers
1k views

New PRG from old

Is the following statement true: If $G: \{0,1\}^k \to \{0,1\}^n$ is a PRG, then so is $G':\{0,1\}^{k+l} \to \{0,1\}^{n+l}$ defined by $$G'(x||x')=G(x)||x'$$ where $x \in \{0,1\}^k$ and $x' \in ...
6
votes
2answers
686 views

Webcam random number generator

I have a question about random number generators. I have read from a real random number generator, based on a webcam ("randcam"). My problem is, that I do not really understand how the generation of ...
6
votes
1answer
211 views

Can a LFSR be cryptographically secure?

I have been looking at an embedded microcontroller which has a cryptographic hardware engine (in particular the PIC32MZ family). These devices have what they advertise as a cryptographically secure ...
6
votes
1answer
342 views

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 ...
6
votes
1answer
595 views

Quality of randomness on a Linux system with haveged

Has anyone checked if using haveged, a Linux daemon which uses the HAVEGE algorithm, changes the non-deterministic properties of the random data from ...
6
votes
2answers
250 views

Unit testing a library RNG and its seeding for practical security

Suppose I have a cryptography library that provides me with a black-box random number generator that is supposed to be suitable for long-lived key generation. (Under the hood it may be assumed to use ...
6
votes
1answer
1k views

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 ...
6
votes
3answers
670 views

ANSI X9.31: the purpose of the date/time vector in the PRNG?

What is the exact purpose of the date/time vector $dt$ in the ANSI X9.31 PRNG? $$ I := E_K(dt) $$ $$ R := E_K(I \oplus V_{old}) $$ $$ V_{new} := E_K(R \oplus I) $$ Specifically, the document seems ...
6
votes
1answer
245 views

What exactly could be accomplished with a backdoor in Dual_EC_DRBG?

Assume that some entity really holds the private key corresponding to the recommended/dubious constants of Dual_EC_DRBG. According to this presentation, they would be able to reconstruct the internal ...
5
votes
8answers
1k views

Would it be secure to use random numbers from random.org in a cryptographic solution?

Random.org provides true random numbers through an unsecured web service. Since these numbers would be transmitted in plaintext could they still be considered useful as true random numbers while ...
5
votes
9answers
838 views

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 ...
5
votes
4answers
427 views

How to prove the security of the PRNG?

Are there any realties tests or criterias that prove the security of the PRNG? What kind of tests or criteria?
5
votes
3answers
3k views

Can Pre-Paid Cards be cracked?

Is it possible to deduce the original function that used to generate those prepaid cards number that are used for charging your mobile phone credits? For example: If I've collected about 1000 of ...
5
votes
3answers
334 views

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 ...
5
votes
2answers
148 views

Fast post-processing for broken RDRAND

Let's assume that the Intel RDRAND instruction does not return fully random numbers, e.g. because it has been engineered with a backdoor for the NSA. If the Intel RDRAND instruction is used directly ...
5
votes
2answers
459 views

How many bits can be safely extracted from the BBS generator at each step?

The Blum-Blum-Shub generator is a deterministic Pseudo-Random Bit Generator with security reducible to that of integer factorization. Setup: Secretly chose random primes $P$, $Q$, with $P\equiv ...
5
votes
1answer
205 views

How can I take advantage of repeated patterns in non random RSA prime factors?

I am researching vulnerable RSA moduli which are composed of primes generated with poor entropy. Having a list of these primes I searched for variable sized repeated patterns among them and I noticed ...
5
votes
2answers
216 views

Relation between key size and PRNG state size

Some (supposedly) cryptographically secure PRNGs have an internal state of only 160 bits or less. When the algorithm is otherwise properly designed, that seems like enough to generate a 128 bit key ...
4
votes
4answers
902 views

What is an efficient random number generation algorithm

I have been looking for the algorithm that generates random number and this algorithm has to be more secure. I am going to use this algorithm to generate the salt that will be used in PBKDF2. ...
4
votes
4answers
466 views

Why isn't the alternating step generator used more often?

According to the Wikipedia entry for the Alternating Step pseudorandom number generator, there is no public cryptanalysis for this device since it was invented back in 1987 by C.G. Gunther. I have ...
4
votes
2answers
258 views

Good enough deterministic PRNG based on hashes

Lets say I have a seed named iv which has a decent amount of entropy. Are there any glaring issues with the following? First 64 bytes are generated by SHA512(iv) Next 64 bytes are generated by ...
4
votes
2answers
331 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
votes
1answer
344 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 ...