C#•3y ago

Generating random numbers (int32) [Answered]

As you may know Guid.NewGuid() returns a 128bit random "number" which is very unlikely to get duplicates of. I need the same behaviour for 32 bit numbers, what's the best way to achieve that? To just use plain old Random#Next() ? Or use Guid#GetHashCode() ?

22 Replies

Unknown User•3y ago

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DustyOP•3y ago

well the more random the better so that method would provide the most random numbers in that bit range?

Monsieur Wholesome•3y ago

Random#Next works just fine For .NET (Core) at least

DustyOP•3y ago

so what would produce "more random" numbers? RandomNumberGenerator or the normal Random class approach?

Monsieur Wholesome•3y ago

Think about that question for a second If something is random, it is random If it isn't random, it isn't random And both are random

ero•3y ago

there are predictable randomnesses

DustyOP•3y ago

That's not exactly true. The random class produces random numbers according to the seed you give it. If you omit the seed it uses the current time (and maybe some other factors to generate that seed). So the randomness there is predictable. And you shouldn't use it for cryptographic usecases, for that RandomNumberGenerator is better suited So my guess is RandomNumberGenerator produces less predictable random numbers but that's why I'm asking here as I'm not an expert

Aeon Vex•3y ago

randomness in cryptography is more about not being able to determine state from the output rather than being more random, although in some sense that is the result of being more cryptographically secure point is for many usecases Random will be just fine, though it's not thread safe if that's a concern for you

DustyOP•3y ago

Thanks for the explanation

Auger•3y ago

RandomNumberGenerator generates a cryptographically secure random number. Random doesn't, and just meets a certain statistical randomness requirement using some subtractive method

DustyOP•3y ago

So to sum it up

// Overall more "random"
return RandomNumberGenerator.GetInt32(int.MaxValue);
// than this
return Random.Shared.Next(int.MaxValue);

// Overall more "random"
return RandomNumberGenerator.GetInt32(int.MaxValue);
// than this
return Random.Shared.Next(int.MaxValue);

right?

Auger•3y ago

It depends, are you wanting more predictable or uniform randomness

DustyOP•3y ago

Well I'm not exactly sure. Let's say I have both running for x amount of time. Which is more likely to hit the same number in the timespan? If you can say that in general

Auger•3y ago

I'd recommend giving this a read, and picking which fits your purpose best: https://khalidabuhakmeh.com/creating-random-numbers-with-dotnet-core Sounds like you don't need something focused on security, and instead need more uniformity.

DustyOP•3y ago

I'm a bit confused now. What I understand is that the RNG class generates random numbers which aren't predictable (=don't rely on system clock etc) which makes sense. But has a less uniform distribution than the Random class

Auger•3y ago

That's right It's also faster

DustyOP•3y ago

So if I understand that correctly, RNG is more likely to produce the same number twitce but you cannot predict it. The random class is less likely but is predictable hence the seed is that correct?

Auger•3y ago

That's correct from my understanding

DustyOP•3y ago

another question then, is the seed from the Random.Shared instance random enough or should I rather use my own random instance and generate a seed each time?

Auger•3y ago

It's good enough I typically always use Random.Shared, and specify my own seed if I need to know what it will create for some reason, like a test

DustyOP•3y ago

Got it thanks for the detailed explanation really appreciate it

Accord•3y ago

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Generating random numbers (int32) [Answered]