how to use RSA or des,md5 TO make a random number generator?

I wouldn't use any of them to make a random number generator: none of them generate data which is random. It may look it, but statistical analysis will almost certainly show patterns - which is not what you want in a random number generator.

Why not just use the Random class[^]?

private Random rand = new Random();
...
for(int i = 0; i < 10; i++)
   {
   Console.WriteLine(rand.Next(100).ToString());
   }

Will give you 10 random numbers between 0 and 99 inclusive.

[edit]"not" inserted in the phrase "which is not what you want in a random number generator" How could I miss that? Easy... - OriginalGriff[/edit]