A better way to generate random numbers (Swift)

I was looking for a better way to generate random numbers in swift.

I did some research and found that the majority of pseudo-random number generators get the current time value and use the reminder operator (sometimes plus an integer value) to return a very low quality casual number.

e.g.

(timevalue % (upperBound - lowerBound)) + lowerBound

But this gives us a pseudo-fake number.

Is there any other way to generate better random numbers?

I would also like to create a "polar" random number generator:

polarRandom(between: NSRange, strength: CGFloat) -> Int

which returns random numbers in the range but with a higher probability (determined by strength) of returning values near the upper and lower bounds.

And a middle polar generator which has a higher probability (always determined by strength) of returning numbers near the middle part of the range:

middlePolarRandom(between: NSRange, strength: CGFloat) -> Int

Please don't blame me for the names of this functions, I didn't sleep well last night...

Any advice is appreciated : )