UTXO checkpoint transactions

The concept discussed involves introducing a new mechanism for fast-synchronizing extremely lightweight nodes in the Bitcoin network through the use of UTXO checkpoint transactions. This innovative approach requires someone to submit a transaction that includes not only a large fee but also a hash of the Unspent Transaction Output (UTXO) set accompanied by the block height as an opcode parameter. The key aspect of this proposal is that miners would be incentivized, or rather obligated, to only include such transactions if the provided hash matches the actual hash of the UTXO set at the given block height.

This method suggests imposing a high cost factor on creating these transactions, equating it to the expense of processing a 100KB transaction, to prevent abuse and ensure that only serious submissions are made. The primary goal here is to enable nodes, especially those with limited resources, to quickly synchronize with the blockchain by leveraging checkpoints that are several months old. The underlying assumption is that it would be simpler and more efficient for nodes to find and utilize these aged checkpoints to update their state to a relatively recent point without needing to process the entire blockchain history.

However, this proposal raises the question of whether there's an actual demand or necessity for such a feature within the current ecosystem. It implies a need for further discussion and consideration regarding its practicality and potential impact on the network. The idea aims to address specific challenges faced by lightweight nodes but also calls for careful evaluation of its implications and feasibility before any concrete steps are taken towards implementation.