In our recent series of lessons, the topics we’ve been covering have consistently been focused on the Rollup family of concepts. This is a massive system that supports the core operations of today’s crypto ecosystem. Today’s topic is still from the Rollup series, and its name is “Rollup Security Inheritance.” Today’s piece can be treated as a more “soul-level” chapter within the Rollup series—because it clarifies one key question: where does a Rollup’s security actually come from? When we talk about Rollups, we often hear a sentence like this: Rollups inherit the security of Layer 1. But this sentence is actually extremely “abstract”: What does “inherit” even mean? What exactly is being inherited? And what parts are actually not truly inherited? If we don’t explain this clearly, it’s very easy to misunderstand Rollups as “a faster Ethereum clone,” rather than a security architecture that is deeply bound to L1.
First, we have to break a common intuitive misconception: Rollup ≠ a brand-new blockchain. It is more like: executing off-chain settling on-chain outsourcing security to L1 as an execution layer You can understand the relationship as: L2 = execution layer L1 = settlement layer + arbitration layer A Rollup itself does not need to build a complete consensus security system. Its security comes from three things: data ultimately being posted on-chain state changes being verifiable disputes being adjudicated by L1 This is the starting point of “security inheritance.” We can break L1 security into several dimensions: data immutability verifiable state transitions economic punishment mechanisms consensus-level attack resistance What Rollups truly inherit are the two most critical layers. So-called settlement security is essentially one sentence: who holds the final interpretive authority? In the Rollup architecture, that authority is tightly locked inside L1 contracts, rather than being handed to any centralized operator. When many people first encounter Rollups, they often get confused: since transactions happen on L2, does that mean L2 nodes can “call the shots”? The answer is—no. Because whether it’s Optimistic or ZK Rollup, they must obey three iron rules: the state root must be written to L1 assets must be escrowed by L1 contracts withdrawals must pass L1 rule verification This is equivalent to putting a pair of “cryptographic handcuffs” on L2. The Sequencer of course has certain power: it is responsible for transaction ordering it determines the batching rhythm it influences user experience But it can only decide “order,” not “ownership.” Let’s take an extreme scenario: if the Sequencer maliciously modifies your balance, the L1 contract will directly reject that state root; if it deliberately freezes your withdrawal, you can take the forced exit path; if it goes offline and runs away, anyone can reconstruct the system based on L1 data. So in the security model: the Sequencer is more like a “front-desk teller,” while L1 is the “notary office + central bank vault.” This is also the biggest difference between Rollups and traditional sidechains. A sidechain’s security model is: it produces its own blocks it runs its own consensus it is responsible for its own assets Once sidechain validators behave maliciously, assets are basically unsalvageable. But a Rollup’s model is: execution on L2 arbitration on L1 assets anchored on mainnet The difficulty of attack upgrades from “taking down a small chain” directly to “breaking Ethereum-level security.” This is what people call the security downgrade impossible triangle—you can be slower, you can be more expensive, but you cannot be less secure. Many people only stare at “proof mechanisms” when talking about Rollups, but ignore a more fundamental layer: data availability. If transaction data cannot be obtained, even the most perfect proof is meaningless. The core design of Rollups is actually very simple: permanently keep the raw materials of the ledger on L1. Imagine a scenario: you see on L2 that your balance is 10 ETH, but the operator refuses to provide your transaction history data. In that moment: you cannot prove that the 10 ETH truly exists, you cannot compute the correct state, and you cannot initiate a forced withdrawal—this is the fatality of data unavailability. So mainstream Rollups all follow one principle: transaction calldata is posted to L1 or stored in an equivalent DA layer, and anyone can download it and replay it. This guarantees three rights: the right to verify: third parties can independently validate the right to exit: users can prove their own assets the right to take over: the community can rebuild the network This is also the most hardcore part of Rollups. Even if the worst case happens: the team disbands the domain expires servers are shut down As long as L1 still exists, users can: generate Merkle Proofs based on the data, and force withdrawals through L1 contracts, or deploy a new Sequencer to take over. So we often say: Rollup security is not “trusting the team,” but “trusting math + L1.” This forms a fundamental divide versus CeFi and sidechains. But if we only talk about “inheritance,” that becomes misleading. Rollups do stand on the shoulders of L1, but they are not perfect replicas of L1. Right now, most Rollups are still: single Sequencer semi-centralized ordering potential MEV capture This can lead to: front-running risk queue-jumping transactions unfair user experience L1-level censorship resistance and neutrality have not yet been fully inherited by Rollups. L1’s security assumption is: many nodes online long-term + economic incentives. But Rollups in reality: Sequencers can go down provers can be delayed exit channels have time costs This belongs to “process-layer risk,” not “final-layer risk.” L1 security comes from: native token staking decentralized validators long-cycle game theory Rollup security relies more on: contract rules fraud/validity proofs DA guarantees The two are not equivalent. A more precise definition is: Rollups inherit the final adjudication power over assets and state, not every attribute of the execution process. In other words: result layer = L1-grade security process layer = L2’s own capabilities This is also why: Sequencer decentralization, shared sequencers, Based Rollups, PBS mechanisms… will become the key narratives of the next stage. The security assumption is: at least one honest challenger + data is always available + L1 can execute Fraud Proof. The core logic is: assume correctness first, then correct if something goes wrong. The security assumption is stronger: every state update comes with a validity proof, and L1 only needs to verify mathematical correctness. Here, the inheritance method is: treat L1 as a cryptographic verifier—no need for social-layer monitoring, only trust math and circuits. A More Intuitive Analogy L1 is the supreme court Rollups are local executive agencies local agencies can work efficiently, but all rulings must: be filed to the supreme court and accept final adjudication, and must not conflict with the constitution. That is the real meaning of Security Inheritance. Written at the End Understanding Rollup Security Inheritance is essentially understanding one sentence: the source of trust for a Rollup is not on L2, but on L1. Layer 2 is responsible for efficiency, Layer 1 is responsible for justice. This division of labor is the real art of blockchain scaling.A Rollup Is Not an Independent Chain
What Exactly Is Being Inherited?
1. Settlement Security — The “Last Line of Insurance” for Rollups
1) The Power Boundary of the Sequencer
2) The Fundamental Difference vs Sidechains
2. Data Availability Security — The True Foundational Moat
1) Why Is Data More Important Than Proof?
2) Anti-Rug Mechanism
What Is NOT Inherited — The Truth That Must Be Faced
1. Centralization of Transaction Ordering
2. Liveness Risk
3. Differences in Economic Models
Two Different Inheritance Paths
1. The Optimistic Path
What is inherited: L1’s arbitration ability and the credibility of economic punishment2. The ZK Path
