Jason just released a developer preview of “Quantumroot” - which if I’m reading it right means BCH can start building quantum resistant vaults (at very impressive levels of economic efficiency / low fees) into all wallets after the 2026 upgrade (provided all relevant upgrades lock in).
Would be amazing if BCH is already rolling out quantum resistant protection options & tooling by the end of next year. I think that should put us nicely ahead of the game & hopefully attract industry attention to our innovations.
I’m sure he’ll jump in with his own comments at some point.
Jameson Lopp’s proposed under-development Quantum BIP.
The proposal is to announce a sunset date at which non-quantum coins become unspendable, rather than letting a quantum attacker grab them and dump. But this by default burns all coins of anyone who doesn’t migrate to the quantum version in the meantime (Satoshi, people not following things closely etc.).
Interesting take on it.
Hunter Beast has published his proposal “Hourglass” in a draft format. The idea is to limit P2PK spends (ie Satoshi & other early coins, 1.7m total) to 1 output per block. This would slow down quantum harvesting of those coins to take nearly a year, instead of happening potentially within just a few hours.
The only downside is that it essentially deprecates P2PK, but that’s already been dead for years.
Seems like an excellent proposal to me at first consideration.
As BCH has no issue with hardforks, we could even consider a variant of this like limiting the P2PK spend to only once every X blocks (like once per 10) to slow things down further, although that might introduce mining games since there would possibly be a huge benefit to reorging that “special” block which harvests the 50 BCH from early P2PK addresses.
Edit: this proposal has anti-synergy with 1 minute blocks, which would again speed up the release of such coins (although it would be slower than without any hourglass).
Edit 2: A good counterargument by Jameson Lopp:
I think this could benefit from a lot more blockchain analysis in order to support the claim that it will reduce economic volatility. On its surface it feels like a half measure.
Sure, requiring P2PK output spends to be spread out over a year /could/ slow down the /tail end/ of said economic volatility. This is assuming that post-QDay, the machines doing the cracking can crack a key in less than 10 minutes.
However, a rational quantum adversary will seek to maximize their revenue. For example, the most valuable likely lost funds are 12ib7dApVFvg82TXKycWBNpN8kFyiAN1dr which has 31,000 BTC spread across only a handful of UTXOs. It’s not a P2PK address, but a P2PKH with an exposed pubkey due to address re-use. Even if this proposal is implemented we can still expect massive economic volatility at the front-end of the quantum era. Even if this proposal was extended to INCLUDE spends from re-used addresses, that would be 31,000 BTC in an hour or two.
Moving on to P2PK specifically, I’d expect a similar issue of front-loaded volatility once a quantum adversary runs through the high value reused addresses that haven’t migrated to a quantum safe scheme. Take, for example, James Howells’ funds at 198aMn6ZYAczwrE5NvNTUMyJ5qkfy4g3Hi - 8,000 BTC spread out across just 16 UTXOs, which would be spendable in a 3 hour timeframe in this proposal.