If sha256 was somehow cracked, we would just fork to a new algorithm.
Don't let quantum fud shake you out of your coins.
Discussion
Sha512
Sir if encryption is cracked bitcoin is the least of my worries
i heard this line touted a lot but it's a wholly unimpressive argument. most systems are trivial to upgrade to higher and higher keysizes way faster than how q computers can progress. and they almost immediately gain the security benefits of such upgrade without a long migration period that can never be truly completed.
You telling me you have faith in cybersecurity practices around the world and this is in the case its out in the open if qc was done in stealth than what the arguement bitcoin to not be the target in case of encryption being broken makes perfect sense to me
If you're talking about cracking the computation of private keys from public keys, you'd still have to add entropy to your private key and move your coins to a new address.
But I think the OP meant cracking mining, which is what uses sha256. The private key to public key function uses elliptic curves and sha256 (twice).
If that is cracked nothing is safe.
All Fiat banking, all information systems, defense systems, nukes, etc.
If you had the power to do this, you could hold the world for ransom.
If you had this power, why only go after Bitcoin, why not go after everything?
Because people would race to create alternatives and everything would be chaos. You might be better of acting like you didn't break it and know all the secrets of your enemy.
sha256 is more important for binary and document integrity than secrets. for example an adversary could alter binary packages and load them with malware and the digital signatures would check out. or just replace transactions or whole blocks in the bitcoin blockchain. that would be some trolling...
I don't remember the details but Steve Gibson of the Security Now Podcast talked about this a long time ago.
Apparently there are researchers that are working on cryptographic algorithms that are difficult for quantum computers.
Maybe of such a crisis occurs we'll have a replacement ready to drop in.
There will be chaos but it's up to each individual to make themselves resilient.