@jimbobway
How would that appear any different than more hashing power added to the network? I'm guessing no one will know that it's broken until someone draws up a proof.
Good point. Depending on the strength of the cryptographic attack, let's supposed 100 blocks where solved in an hour. It would raise a lot of suspicion since 100 is a lot. The bitcoin client would then readjust the difficulty level and all other miners would not solve very many blocks. Miners would complain and most likey the bitcoin dev team would change the algorithm.
But, if 10 blocks were solved in an hour and then the difficulty adjusted it could have been pure luck and there would be no sure fire way to prove it without mathematical proof.
I don't think breaking sha256 is "hacking". It's like a gold miner finding the motherload. However, I think breaking EC would be hacking.
While this is correct, I'd like to point out that as mining moves to mostly ASIC, we will have the problem that any algorithm change will make all this custom hardware worthless. I would think the producers of sha256 hardware would be able to quickly swap out the processors for something tuned to the new algorithm, but it still will be a higher barrier to get around.