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115 votes

Why do some people believe that humans are "bad at" generating random numbers/characters like this?

In short, it is more than a belief: there is strong evidence that humans are not good entropy sources. There is a test for this Man vs. Machine. Or, why Man is not a Particularly Good Source of ...
kelalaka's user avatar
  • 48.7k
67 votes
Accepted

Are one-time pads crackable in theory?

For example, for a target bitstring of 100 bits, I cannot scan all bitstrings of 100 bits and XOR each with the target, hoping to recover the message. This approach will produce all messages that can ...
Maarten Bodewes's user avatar
46 votes
Accepted

What is the practical impact of using System.Random which is not cryptographically random?

You asked for the practical impact, so the answer is that for \$120 I could probably have your entire password database done by tomorrow. Here is your program, or something similar to it: ...
ymbirtt's user avatar
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42 votes
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What does it mean for a random number generator to be cryptographically secure?

What are the criteria that make an RNG cryptographically secure? In short, a DRBG [deterministic random bit generator] is formally considered computationally secure if a computationally-limited ...
Stephen Touset's user avatar
38 votes

Cryptography's random number problem?

The title of this article is complete hype. Tip: when a journalist says “X could solve Y”, read “X probably won't solve Y”. Much of the content of the article is hype too. Cryptography has a random ...
Gilles 'SO- stop being evil''s user avatar
35 votes
Accepted

How can C rand() be exploited if a secure seed is used?

The ISO/IEC 9899:1990 edition of the C standard contains: EXAMPLE     The following functions define a portable implementation of rand and ...
fgrieu's user avatar
  • 142k
34 votes

Why is the output of a True Random Number Generator (TRNG) insecure after it has been compressed?

I think you're misinterpreting the source. The source says the TRNGs "rely" on compression (a cryptographic hash would be the compression function, or possibly some simpler function to ...
Serpent27's user avatar
  • 1,461
32 votes
Accepted

A website that identifies an RNG from its output

A colleague of mine told me about a website that, given a sufficient quantity of output from an PRNG, had been able to deduce which application the PRNG was from. As you correctly identified this ...
SEJPM's user avatar
  • 46.1k
31 votes

Why do some people believe that humans are "bad at" generating random numbers/characters like this?

For me, the fraud-related applications of Benford's Law come to mind. When people make up data they tend to create overly uniform data, even when it's not appropriate. There's a definite psychology ...
thesquaregroot's user avatar
29 votes

A website that identifies an RNG from its output

One tool that tries to do this is untwister. It's almost certainly not the tool you were thinking of, though, as it cannot determine if the output came from OpenSSL specifically. It can determine ...
ChrisInEdmonton's user avatar
26 votes
Accepted

What is the difference between TRNG and CSPRNG?

A True Random Number Generator uses a physical phenomenon not known to be fully deterministic as origin of the discrete values (bits or integer numbers) that it outputs. That phenomenon can for ...
fgrieu's user avatar
  • 142k
26 votes

What is the practical impact of using System.Random which is not cryptographically random?

From what you have described, it sounds like your system works as follows: Consult the system clock to find a 32-bit seed $s$. Use System.Random to generate a ...
Squeamish Ossifrage's user avatar
25 votes

Are one-time pads crackable in theory?

To begin with, your definition of perfect secrecy is non-standard. The standard definition is given in an excellent answer to the question how is the OTP perfectly secure?. Essentially, perfect ...
kodlu's user avatar
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23 votes
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How many hex digits do I need to compare when manually checking hash functions?

How many hex digits do I need to compare when manually checking hash functions? If you actually want the full security guarantees of the hash function to apply: all of them. I usually just look ...
SEJPM's user avatar
  • 46.1k
21 votes

Using Tweets as a Random seed

The other answers provide very good lists of reasons not to use Twitter as an entropy source. What follows is the flip side of your question:- Why would you want to? Tweets are typically read on ...
Paul Uszak's user avatar
  • 15.5k
20 votes
Accepted

Using Tweets as a Random seed

What you are suggesting is not a good idea for a general purpose random number generator. It could be meaningful for very specific use cases if you need a random number generator whose output can be ...
kasperd's user avatar
  • 1,387
18 votes

What does it mean for a random number generator to be cryptographically secure?

What are the criteria that make an RNG cryptographically secure? From en.wikipedia.org/wiki/CSPRNG: Given all outputs so far, there must not be any algorithm that predicts future outputs with ...
Luc's user avatar
  • 1,518
18 votes

What is the practical impact of using System.Random which is not cryptographically random?

The official documentation for System.Random explicitly says it should not be used for generating passwords. It’s predictable, and seeded only from the system clock. This means System.Random has at ...
rmalayter's user avatar
  • 2,297
18 votes

Why do some people believe that humans are "bad at" generating random numbers/characters like this?

Why would a dice rolled be "more random" than simply coming up with a sequence in your head, and then changing some of them? Humans have too many biases regarding what a random sequence is. ...
Jean-Baptiste Yunès's user avatar
17 votes
Accepted

XOR a set of random numbers

Assuming that $b = 2^k-1$ for some positive integer $k$, XORing two (or more) numbers in the range $[0,b]$ will indeed yield a number in the same range. If the numbers are random, uniformly ...
Ilmari Karonen's user avatar
16 votes

Example of cryptography random number

What kind of numbers are needed for cryptography/security? Are those integers? Bits. Simply have your TRNG generate random bits. As mentioned in the other answer, the only difference between bits/...
Ella Rose's user avatar
  • 19.6k
15 votes

Using Tweets as a Random seed

How are you going to decide which tweet to use? Randomly? This quickly leads to a chicken / egg problem. What if the chosen tweet is one word? That would not add a lot of entropy. What if twitter is ...
Maarten Bodewes's user avatar
15 votes

Why do some people believe that humans are "bad at" generating random numbers/characters like this?

Randomness is a measurable, statistical property of a set of values. It doesn't mean the same as "hard for a human to guess." Your sample string is hard for a human to guess, but it isn't ...
JesseM's user avatar
  • 462
14 votes

Are one-time pads crackable in theory?

I'll try a practical example: I trade stocks. Instructions to my broker use a simple Caesar shift cipher, but the shift varies by values in a one-time encryption pad. Common 8-char instructions ...
Alan Campbell's user avatar
14 votes

How can C rand() be exploited if a secure seed is used?

I once played this online game, it was an old-school MUD. You log in, chat, kill some goblins. It had a casino. You go into the casino and you bet X gold, and there was a 40% chance you win double ...
Ron Penton's user avatar
14 votes

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

If you control both ends as well as the transfer channel - for example if you are transferring a large file between two of your own computers via a USB drive - then it's OK to only verify the hash ...
Yolanda Ruiz's user avatar
14 votes

Radioactive Decay, Gaussian or Uniform?

You can just follow the instructions on HotBits, which is exactly what you're trying to build. It's been running for years and is the only radioactive TRNG on the internet. It goes into great depth ...
Paul Uszak's user avatar
  • 15.5k
14 votes

Why do some people believe that humans are "bad at" generating random numbers/characters like this?

People are not that bad, but we're slow. See How were one-time pads and keys historically generated? In summary, MB's of 100% secure key material were generated for one time pads by people simply key ...
Paul Uszak's user avatar
  • 15.5k
13 votes

Examples of frauds discovered because someone tried to mimic a random sequence

Following my comment, and even though it's a bit different from what you ask: I really enjoyed the story here where the use of an incorrect pseudorandom number generator led to the arrest of members ...
Geoffroy Couteau's user avatar
13 votes
Accepted

How to generate random numbers within a range (0,n) from random bits?

If you really are attached to those bits so you want to use more than 101/128 of conversion attempts don't want to do bignum calculations want verfiable bias-free generation then collect 20 bits to ...
Neil_UK's user avatar
  • 408

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