I imagine that once the difficulty gets so high that you're successful hashes start looking like this 000000000000000000000000000000fa that somebody might be able to break SHA256 would they not? Eventually we would find two hash values that were the same but had different inputs. That or Bitcoin would cease to work, right?
At what level of difficulty will we have to change our cryptographic hash function? (When will we have to re-inforce our security?)
To get difficulty high enough that successful hashes need to start with that many zeroes would take more computing power than you can conceivably imagine. Which is the understatement of the century. Reaching maximum difficulty would require a sustained rate of approximately 7*2^224 Mhash. At what level of difficulty will we have to change our cryptographic hash function? (When will we have to re-inforce our security?)