That’s true, but there’s some precedent for picking a block that everyone agrees upon (that exists before quantum computers) and changing the rules at that block to prevent someone from rewriting the blockchain. A lot depends on how much warning we have.
It looks like making a cryptocoin that can survive quantum computers might be a high value activity.
In particular, the ability to roll back the blockchain breaks the patches you’ve mentioned for the fact that QC also breaks elliptic curve crypto.
That’s true, but there’s some precedent for picking a block that everyone agrees upon (that exists before quantum computers) and changing the rules at that block to prevent someone from rewriting the blockchain. A lot depends on how much warning we have.
It looks like making a cryptocoin that can survive quantum computers might be a high value activity.