# Tag Info

### 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 ...
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### Can you use memory errors as a source of randomness for cryptography?

(..) would it be viable to allocate a very large amount of memory (perhaps in a long loop) and use the errors that eventually occur as a source of randomness? No. Practical use of memory errors as a ...
• 125k
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Accepted

### The GCD strikes back to RSA in 2019 - Good randomness is the only solution?

The solution is simply to make sure that you have good randomness. At the size of the numbers we are considering, the probability of a repeat when using good randomness is extremely small. To make ...
Accepted

### Is it safe to seed a random number generator from system time?

Yes, it is unsafe to seed a PRNG with only with the system time. No, that's not all Bouncy Castle's SecureRandom does. The ...
Accepted

### RFC6979: error in reference implementation?

The RFC specifies things in terms of bits. Each call to HMAC outputs hlen bits. tlen is the count of bits obtained so far; when ...
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### What is the difference between CSPRNG and PRNG?

The key element in the definition of a PRG is the observer (aka distinguisher, algorithm, test, etc) that the PRG is supposed to fool. A statistical PRG fools a specific set of observers, whereas a ...
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### Entropy of two concatenated random values

Even in context, much of what is written in the blog post makes no sense. E.g., it says: While it can be argued that the DRNG is in reality just splitting a 128-bit value into two pieces and ...
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### Where do Windows applications get entropy from?

Update: Since I wrote this post, CryptGenRandom has been deprecated. Apparently it is now recommended to use BCryptGenRandom ...
• 31.3k
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### Why does BCRYPT_RNG_DUAL_EC_ALGORITHM get removed from CNG API on Windows 10?

The Government's elliptic curve backdoor is real, isn't it? We don't know for sure, but there are indicators into that direction. More importantly though, yes, you can backdoor the RNG, as was ...
• 44.7k
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### Is openssl rand command cryptographically secure?

Yes, it is cryptographically secure, pseudo random output, seeded by retrieving secure random data from the operating system. If it is random or not depends on the fact if the OS RNG is random. This ...
• 85.8k
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### Mixing Entropy Sources by XOR?

If one source remains uncompromised plus statistically random on all bits, and both sources remain independent, then a xor of both sources together can also be ...
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### 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 ...
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### 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. ...

### What tests can I do to ensure my random number generator is working correctly?

What tests can I do to ensure my PRNG is working correctly? That depends on what exactly you mean by “working correctly”. You can do statistical tests to check for various statistical flaws your ...
• 17.4k
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### Does using modulo (%) affect quality of randomness?

Let me begin by saying that if you have a hardware source of randomness, you don't need to be stingy with it. 1) Does modulo affect the quality of randomness, faking in some way the distribution of ...
• 4,198