But what is to stop some of those addresses from being the same?
- Randomness
- An extremely large set of potential addresses that can be created
- The fact that if the most efficient technology possible (based on our current understanding of physics) were to somehow harvest all of the energy of the sun, all of the possible Bitcoin addresses would not be generated after a thousand years
All these points are based on probability.
But I want to know how sure a repeated bitcoin address is prevented?
I knew bitcoin address can be generated in offline too.
I guess a time based and System ID or/and IP based coding must be there to prevent a repeated address.
There is nothing that will prevent the same address from being generated more then once. Assuming that your private key is generated in a truly random way then the chances of this happening are nearly zero.
If the method that you use to generate private keys is somehow flawed (eg you use a weak random number generator) then the chances of generating the same private key as someone else would increase.
You need to remember that it is always possible that one person may wish to use the same address across multiple computers/locations, and that the network does not actually do anything when a new address is generated (addresses can be generated offline).