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I just figured out a way to create a RNG that may be almost as good as TRNG (true random number generator) and need some input to confirm/clarify.

What if I use the IPv6 address of a visitor as a seed + the time recorded when the visitor executes a particular action at my website to generate the random numbers?

IPv6 has about 340 trillion trillion trillion possible addresses.

And I increase the strength by repeating the same process with a 2nd visitor and do some logic between 1st visitor's RNG and 2nd visitor's RNG to arrive at a new RNG (say "1st New").

And I continue with the same process on 3rd visitor and do some logic between 3rd visitor's RNG and "1st New" to arrive at another new RNG (say "2nd New").

And I continue with the same on subsequent visitors until a certain duration is reached, to arrive at a final RNG (say "Final New").

Is this "Final New" almost as good as TRNG? Or is it at least as good as CSPRNG?

For a hacker to successfully brute force my RNG, he needs to know the specific IP addresses of my visitors, at certain time period when a particular (unknown) action is executed, per each different visitor, for a duration of time, and the logic used in computing the RNG from one visitor with the next.

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closed as off-topic by fgrieu, fkraiem, e-sushi Oct 26 '18 at 7:31

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  • $\begingroup$ If you're looking for a non dedicated hardware TRNG, investigate haveged. It kinda builds upon internal system timings somewhat like your access times. $\endgroup$ – Paul Uszak Oct 25 '18 at 21:07
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Is this "Final New" almost as good as TRNG [or CSPRNG]?

Assuming proper cryptographic techniques for entropy combination (eg Fortuna or at least hashing) are used for the combination of the "RNGs" the answer is no. If this kind of processing is not used, then the answer is an even bigger NO.

The reason here is relatively simple, the combination of IPv6 adress paired with the timing of the visit isn't actually a secret only known to you. Whoever hosts your VPS / your physical machine / provides you with internet connectivity or provides your ISP with internet connectivity can collect the very data you are considering random. And in cryptography the job of a TRNG / CSPRNG is to provide unpredictable random bytes, which is clearly violated here, because some or more of your network / system operators can predict the "random" bytes.

Additionally, while there are indeed $2^{128}$ IPv6 adresses, only a tiny fraction of these are used by actual end-users, so they're indeed not as unpredictable as assumed. Also because IPv6 has such a vast adress space, end-users tend to get static adresses (unlike with IPv4 where they are actually dynamic quite often) and so if you have a standard set of users, their IPv6 adresses won't give all that much unpredictability.

However, if you really want to use this idea, you can still measure this data (the IP + time pair and maybe also do this for IPv4?) and feed it to your operating system as additional entropy / seed data, which can't hurt security due to the way this data is used by the OS.

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  • $\begingroup$ I've considered using IPv4 too but despite being dynamic it has a total of several billions addresses only, making any brute force attempt fairly easy. $\endgroup$ – Dorky Oct 26 '18 at 2:59

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