Jul 10, 2012 Today I'll be showing you how to create your own random number generator in C. Visit my website at http://www.thekasattack.comyr.com. Little snitch download. Why OpenSSL can't use /dev/random directly? How bad it is to feed /dev/random with /dev/urandom? Has use of /dev/urandom instead of /dev/random ever caused a vulnerability? Auto tune real time free. Entropy change when reading from /dev/urandom vs /dev/random. Hot Network Questions.
Dev Random Example
![Using Using](/uploads/1/2/6/1/126179664/343431651.jpg)
C++ Random Example
I am soon to write the FAQ on <random>, but the simple answer is that rand() stinks.
The main problem for distribution is that people don't know how to properly get a random number from rand() -- there is no magic library code to do it for you -- and most people get it Wrong.
The next is that rand's range is often significantly smaller than you want it to be.
You can read all about rand() on it's FAQ:
http://www.cplusplus.com/faq/beginners/random-numbers/
If you want to get technical, rand() implementations tend to favor lower bits, which leads to biased numbers.
The C++ <random> library gives you much more powerful PRNGs with a lot of built-in ways to draw numbers from them without bias.
The most difficult thing to do is seed it properly. Unfortunately, people still depend on the clock -- which is a mistake, but acceptable for video games and the like -- anything that doesn't require statistical correctness (like Monte Carlo simulations and the like).
You need to warm up your Mersenne Twister.
Hope this helps.
The main problem for distribution is that people don't know how to properly get a random number from rand() -- there is no magic library code to do it for you -- and most people get it Wrong.
The next is that rand's range is often significantly smaller than you want it to be.
You can read all about rand() on it's FAQ:
http://www.cplusplus.com/faq/beginners/random-numbers/
If you want to get technical, rand() implementations tend to favor lower bits, which leads to biased numbers.
The C++ <random> library gives you much more powerful PRNGs with a lot of built-in ways to draw numbers from them without bias.
The most difficult thing to do is seed it properly. Unfortunately, people still depend on the clock -- which is a mistake, but acceptable for video games and the like -- anything that doesn't require statistical correctness (like Monte Carlo simulations and the like).
You need to warm up your Mersenne Twister.
generator.discard(10000)
or so.Hope this helps.