Blockchain Layering: We need our own Consensus

Exploring the evolution of consensus mechanisms in blockchain from L1 to L2, and how to design suitable consensus mechanisms for proprietary AppChains to achieve a balance between decentralization and performance. (Background: Breaking the human millennia-long consensus and mindset: why Bitcoin is a better "gold") (Context: Gold breaks the historical high of $4200! Silver also breaks records, is there an endless surge in safe-haven assets?) In the world of blockchain, the consensus mechanism pumps the vitality of the entire system like a heart. It is not just a technical protocol, but the cornerstone of building trust. As blockchain evolves from a single Layer 1 (L1) to a multi-layer architecture, we increasingly realize that a one-size-fits-all consensus design can no longer meet the diverse needs of a layered ecosystem. The iron law of L1 may apply to the foundation, but L2 and even proprietary AppChains require tailored "consensus philosophy". This article will start with the basic concepts of blockchain consensus, gradually explore the consensus characteristics of L1 and L2, and extend to the design ideas of proprietary AppChains, aiming to provide developers with a more pragmatic framework: we need our own consensus. What is blockchain consensus? The core of blockchain consensus lies in how to reach an agreement on the ledger state among nodes in a decentralized network, thereby realizing the state transition and data storage in a decentralized manner. It is not a simple voting mechanism, but a series of steps that ensure the network's security, liveness, and consistency. Traditionally, the consensus process can be broken down into four key stages: admission consensus, block consensus, final consensus, and exit consensus. Admission consensus: Determines who is qualified to participate in the network. Typically, this is done through economic thresholds (such as collateralized assets) or computational proofs (such as PoW) to filter nodes and prevent malicious participants from easily entering. Block consensus: Focuses on generating new blocks: nodes compete or collaborate to bundle transactions, forming candidate blocks, and mechanisms like Proof of Work (PoW) or Proof of Stake (PoS) select the winner. Final consensus: The conclusion of the entire process, confirming the irreversibility of the blocks, often utilizing variants of Byzantine fault tolerance (BFT) to handle divergences, ensuring that the chain accepted by the majority of nodes becomes the "main chain". Finally, exit consensus handles the departure of nodes: it may involve slashing collateral or graceful exit rules to maintain the long-term health of the network. These steps seem linear but are interconnected, forming a closed loop. Understanding them is not only foundational for L1, but also paves the way for layered architectures. Because in the world beyond L1, the "purity" of consensus can be compromised, but its essence—the guarantee of decentralization—never goes out of date. L1's Consensus Characteristics Layer 1 blockchains, like Bitcoin or Ethereum, represent the pinnacle pursuit of blockchain technology: nearly the highest level of trustless (no trust cost). It is an absolute independence that transcends national sovereignty and any entity level. It requires systems to operate within the confines of formal logic, introducing no external dependencies of non-formal logic beyond mathematical theorems and game theory models. Imagine if an L1 consensus relies on a centralized entity; it then degenerates into a "wolf in sheep's clothing," potentially subject to regulation or disruption. Therefore, the consensus design of L1 is extremely rigorous. PoW ensures randomness and security through computational power games, while PoS maintains honesty through economic incentives (Note: the author does not fully endorse PoS consensus, despite it being the mainstream approach currently). These mechanisms do not trust human intentions but trust probability and punishment. The result is high costs—energy consumption or capital lockup—but what it gains is sovereignty-level robustness. L1 is not born for efficiency but fights for eternity. It is the "constitution" of blockchain, untainted. However, when we turn to Layer 2, the philosophy of consensus begins to loosen. The absolutism of L1, while great, should not be rigidly applied. The L2 ecosystem is more application-oriented and needs to seek a balance between security and efficiency. This raises a key question: What kind of consensus does L2 actually need? L2's Consensus: Why It Is Needed and How It Differs from L1 L2's consensus is not an optional embellishment but the backbone of decentralization. Many mistakenly believe that zero-knowledge proof (ZK) technologies such as zkVM or zkEVM are sufficient to ensure L2's security—they are indeed powerful and can efficiently verify the validity of transactions. However, validity proof only addresses the issue of "whether the transaction execution result is correct" but overlooks the more challenging issue of censorship resistance. Censorship is not a computational error but a power intervention: a centralized sequencer can arbitrarily delay or reject transactions, and no matter how rigorous the zk proof is, it cannot save the day. Moreover, pure centralized L2 has numerous hidden dangers. It can easily fall into the Crash Fault Tolerance (CFT) trap—single point failures leading to a network-wide crash. To this end, many Rollup projects are equipped with "escape pods" or forced withdrawal functions: users can withdraw assets unilaterally when anomalies are detected. This is nothing but a reluctant patch under centralization, not a long-term solution. If L2 is completely centralized, how is it different from a centralized exchange? The safety of user funds is tied to a few nodes, and the risk of censorship looms large. Of course, L2's decentralization does not need to compare with L1's absolute height. L1 needs to resist global sovereignty, while L2 can leverage it to pursue "relatively trustless". This does not mean that L2 can embrace centralization in one fell swoop—this would sacrifice the core values of blockchain. Instead, we should design a moderate consensus: sufficiently decentralized to resist censorship, yet not losing performance advantages. How to Design L2's Consensus When designing L2 consensus, we must first face the reality: L1 surpasses L2 in security, decentralization, scalability, and abstraction. L2's security is inherently weaker than L1; it is more scenario-oriented and can tolerate higher customization and performance pursuits. But this is not a disadvantage; it is an opportunity. L2 has a unique asset: L1 as a theoretically trusted source. We can leverage L1's data or state as input anchor points for L2 consensus, thereby ensuring L2's security with L1's iron laws. This is a methodology of "layered leveraging," far superior to reinventing the wheel from scratch. Here, the author presents an example: In the admission consensus phase, we can set the chain data or digital assets (such as BTC, ETH, USDT) on L1 as the threshold. Nodes need to burn/transfer/collateralize L1 assets or prove their activity on L1, which not only filters low-quality participants but also injects L1's economic security into L2. Block consensus can cleverly integrate L1 elements to ensure randomness and fairness. For instance, through specific operations on L1—such as burning tokens or transfers + some protocol algorithms on L2—to generate random seeds, determining which node will produce the block. This makes L1's randomness a shield for L2's randomness. As for final consensus, many PoS public chains adopt a type of BFT mechanism here: the engineering workload is enormous and the mechanism is complex, yet the security is still inferior to L1. We need not imitate. Instead, we can upload the blocks produced after the block consensus to L1 according to custom verifiable fork choice rules, periodically finalizing them. Once the L2 block is confirmed on L1, it becomes irreversible—L1's finality equals L2's finality. This simplifies the design, avoids the complexity trap of BFT, yet forges a solid unity with L1's strength. This L2 consensus...