Revise Hourglass V2 proposal for clarity and details

[theblackmarble]

Refine the Hourglass V2 proposal to clarify spending rules and motivations regarding quantum vulnerabilities. Update activation details and backward compatibility information.

[cryptoquick]

Some more clarification is needed around activation, especially BIP-8 LOT default recommendation based on the game theoretic implications regarding economic nodes.

Also would love to directly quote and attribute the private property promise... Here are my notes on that:

Bitcoin's Social Contact - The Private Property Promise - waxwing's

1/ coin inflation schedule is set in stone;

2/ if you can cryptographically validate a transfer, bitcoin will let you do it, i.e. you can always spend your own money;

3/ if you "locked" a utxo with a certain ruleset in the past, that ruleset will still be active and let you spend in future, i.e. you can't be locked out of your own money.

I reformatted that here

I love Waxwing's outline of what people often describe as "Bitcoin's Social Contract - The Private Property Promise" -- If I might refine the language a bit further, and I'm happy to iterate on this (it also crushes some nuance), but generally it could be said:

1. The subsidy issuance schedule must be immutable. The supply must be 21 million, no more, no less.
2. If you can cryptographically validate a transfer, the network must let you do it. You must always have the capability to spend your own money.
3. If you "locked" a UTXO with a certain ruleset in the past, that ruleset will still be active and let you spend in future. You cannot be locked out of your own money.

Source: https://groups.google.com/g/bitcoindev/c/7jkVS1K9WLo/m/btgqa9t7AwAJ

[cryptoquick]

Suggested change

Non-upgraded nodes will accept blocks containing P2PK transactions that violate the Hourglass rules. For this reason, economic enforcement depends on adoption by a supermajority of the network, as specified in the Activation section. Transactions that would be invalid under Hourglass may still be relayed by non-upgraded nodes prior to activation.

Non-upgraded nodes will accept blocks containing P2PK transactions that violate the Hourglass rules. For this reason, economic enforcement depends on adoption by a supermajority of the network, as specified in the Activation section. Transactions spending P2PK outputs in any way that would be invalid under Hourglass may still be relayed by non-upgraded nodes prior to activation. The vast majority of transactions will remain unaffected. This is only to restrict the throughput of P2PK coin spends in light of a direct violation of Bitcoin's private property promise if the cryptographic assumptions underpinning signature security is some day compromised to such a degree that multiple independent users can spend the same P2PK scriptPubKey (say in the event that a private key could be derived from a public key using a quantum computer, a threat model explained in more detail in BIP 360).

Hopefully this clarifies any ambiguity here. Just a starting point. Feel free to make any changes.