As long as the secret has enough bits, then the risk of collision is so negligible that it's basically zero in our finite world.
I think the concept of just how large some numbers are really sunk in for me when I read this article [1] from Bruce Schneier. One thing I learned was that it would require more energy than the total energy output of the sun just to power a computer to count to 2^256. Ultimately, this quote from that article sums up his point well:
> These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.
I think the concept of just how large some numbers are really sunk in for me when I read this article [1] from Bruce Schneier. One thing I learned was that it would require more energy than the total energy output of the sun just to power a computer to count to 2^256. Ultimately, this quote from that article sums up his point well:
> These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.
[1] https://www.schneier.com/blog/archives/2009/09/the_doghouse_...