Quote from: buwaytress on August 06, 2019, 10:20:52 AM

A bit of a stale topic since even the most optimistic projections give us another decade before such a qc becomes a viable threat... And it is conceivable that Bitcoin would have upgraded significantly by then... Considering the developments of the last decade alone.

I do wonder if all that presumed upgrades would also be retrospective, it would have to be otherwise people who didn't update wallets would risk losing everything.

No quantum-resistant upgrade can retroactively protect vulnerable bitcoins. That's why we're "damned if you do, damned if you don't." Either way, there could still be millions of vulnerable bitcoins held on exposed public keys. The Satoshi coins, for example.

The only way to prevent those bitcoins from being stolen and re-added to the supply would be to lock/destroy them in a fork. For example, we could implement a fork where coins are destroyed if they aren't moved in n blocks -- a number of years down the road maybe. This would be extremely controversial.

Otherwise, the only thing we can do is soft fork in a new signature scheme (like Lamport) and have people voluntarily use it, like Segwit. No matter what, a decade is not such a long time. We should be discussing this stuff today.