Isn't bitcoin still being developed? So can't they just update the cryptography when we get to that point?
I guess I don't really how how much bitcoin can change over time
I guess I don't really how how much bitcoin can change over time
https://en.wikipedia.org/wiki/Bitcoin_Cash
https://en.wikipedia.org/wiki/Bitcoin_Gold
So yes, it is conceivable to change the fundamental algorithms, but it would certainly be experienced as a fork to the extent that not everyone involved in Bitcoin participated.
Also, changing the digital signature algorithm is a bigger and more difficult change than the hashing algorithm in some ways, because you need a strategy to preserve people's existing balances, either one that requires, or one that works without, their active involvement (that is, generating signatures). If there is a feasible attack to forge signatures, then a method that can work without existing Bitcoin owners' involvement will leave them vulnerable to having their holdings stolen by forgeries in the future. You can think of this as somewhat akin to weak RNGs in Bitcoin clients (there have been a couple of these) generating vulnerable private keys -- if legitimate owners knew about the problem before attackers acted, they could act to protect themselves, but if not, not. A feasible signature forgery attack based on a quantum computer would put everyone who owns cryptocurrency wallets based on the vulnerable signatures in a position like that of people using a client with a weak RNG. :-(
Another issue with replacing Ed25519: the best "post-quantum" asymmetric crypto we have so far is a lot less efficient and compact: https://en.wikipedia.org/wiki/Post-quantum_cryptography#Comp...
That'll probably make it more disruptive than, for example, swapping out SHA-1 for SHA-256.