The Spam problem of Bitcoin and Unpermissioned Broadcast Networks in general

The concept of streamlining blockchain transactions and data storage revolves around the efficiency of layering in blockchain technology. The Lightning Network, as an example, operates above Bitcoin's main blockchain (L1), enabling a higher transaction throughput by allowing transactions to occur off the main chain and only settling the final state on-chain. This mechanism suggests that similar principles could be applied between the main blockchain (L1) and a hypothetical lower layer (L0). By committing transactions from L1 to L0, it's possible to discard non-essential data from L1, relieving nodes from the burden of processing and storing vast amounts of historical data. This approach emphasizes the importance of only retaining critical information necessary to verify the integrity of the blockchain, such as proof of work and signatures chains, during the Initial Blockchain Download (IBD).

In this streamlined model, transactions could be simplified as they are passed down the layers. For instance, a transaction chain involving multiple parties (Alice -> Bob -> Charlie) could be condensed into a single transaction (Alice -> Charlie) at the L0 level, with a separate proof for intermediate steps. This is akin to how the Lightning Network simplifies chains of transactions off the main blockchain before committing the final state. Such a method not only makes blockchain data more manageable but also enhances spam resistance by requiring more substantial proofs for transactions, thus deterring frivolous or malicious activity.

The discussion further explores the notion of specialized nodes that operate with reduced data requirements. Unlike full nodes that store the entire blockchain history or pruned nodes that maintain only recent data, these specialized nodes would focus solely on essential information like block headers and proof of work. This specialization could lead to nodes that are inherently more resistant to spam, as they necessitate more significant proofs for coin transactions. The evolution towards such lightweight nodes represents a potential future direction for blockchain infrastructure, aiming for increased scalability and efficiency while ensuring security and verifiability of the network.