[sorry if I haven't replied to the other thread on this, I get swamped by email and don't catch them all]
This solution is workable but it seems somewhat difficult to me at this time. The clock might be implementable on a peer network level by requiring inclusion of a transaction that was broadcast after a 9 minute delay. Usually a 50% hashrate attack is needed to reverse a transaction in bitcoin. With this change, this naively appears to become a 5% hashrate attack, unless a second source of truth around time and order is added, to verify proposed histories with. A 5% hashrate attack is much harder here, because the users of mining pools would be mining only 10% of the time, so compromising mining pools would not be as useful. Historically, hashrate has increased exponentially. This means that the difficulty of performing an attack, whether it is 5% or 50%, is still culturally infeasible because it is a multiplicative, rather than an exponential, change. If this approach were to be implemented, it could be important to consider how many block confirmations people wait for to trust their transaction is on the chain. A lone powerful miner could intentionally fork the chain more easily by a factor of 10. They would need to have hashrate that competes with a major pool to do so. > How would you prevent miners to already compute the simpler difficulty > problem directly after the block was found and publish their solution > directly after minute 9? We would always have many people with a finished / > competing solution. Such a chain would have to wait a longer time to add further blocks and would permanently be shorter. > Your proposal won’t save any energy because it does nothing to decrease the > budget available to mine a block (being the block reward). You are assuming this budget is directly related to energy expenditure, but if energy is only expended for 10% of the same duration, this money must now be spent on hardware. The supply of bitcoin hardware is limited. In the long term, it won't be, so a 10% decrease is a stop-gap measure. Additionally, in the long term, we will have quantum computers and AI-designed cryptography algorithms, so things will be different in a lot of other ways too. _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev