Why Modularity Will Break Today's Bridge Security Models

Monolithic bridges like LayerZero and Axelar assume a single, always-available settlement layer. In a modular stack, the settlement layer is just another service that can fork or halt, invalidating all bridge attestations.

• Who's in charge? A forked settlement chain creates two valid states.
• Cascading Invalidity: Fraud proofs or validity proofs become unanchored.
• Example: A bridge secured by Celestia's data availability has no recourse if Ethereum, its settlement layer, experiences a non-finality event.

Intent-based systems like UniswapX and CowSwap rely on a network of solvers. Modularity unbundles execution, making it impossible for a bridge to verify the correctness of a cross-chain action, only its inclusion.

• Verification Gap: You get proof data was posted, not that the execution was valid.
• Solver Risk: Becomes a centralized trust point for cross-chain intents.
• Attack Vector: A malicious modular sequencer can include invalid state transitions that a light client bridge cannot detect.

The only viable model is a network like Succinct or Polymer that aggregates and verifies proofs across modular components (DA, Settlement, Execution). Security is re-bundled at the protocol level.

• Universal Verifier: A single, battle-tested proof verifier for all modular components.
• Economic Scaling: Security cost is amortized across thousands of chains and rollups.
• Future-Proof: Agnostic to the underlying DA or settlement layer, only cares about proof validity.

Bridges like LayerZero and Axelar rely on a small set of validators for cross-chain security. In a modular stack, a malicious rollup sequencer can censor or reorder transactions before they reach the settlement layer, breaking the bridge's fraud-proof or validity-proof assumptions. The attack shifts from forging a signature to manipulating state before attestation.\n- Attack Vector: Sequencer censorship & MEV extraction on the source chain.\n- Impact: $10B+ in bridged assets reliant on honest sequencer assumptions.

Bridges like IBC and Near Rainbow Bridge use light clients that assume data availability. A modular chain posting data to Celestia or EigenDA can withhold critical state transitions, preventing the light client on the destination chain from verifying the validity of a cross-chain message. The bridge is secure only if the DA layer is live and honest.\n- Attack Vector: Data withholding attacks by the rollup or its DA provider.\n- Impact: Paralyzes ~500ms finality guarantees, freezing funds.

Solutions like UniswapX and Across use fillers to solve user intents. In a modular ecosystem with fragmented liquidity, solvers must route across multiple specialized chains. This creates complex, opaque execution paths where a malicious filler can exploit latency differences between modular components for maximal extractable value, effectively front-running the user's cross-chain swap.\n- Attack Vector: Multi-chain latency arbitrage and sandwich attacks.\n- Impact: -50%+ effective slippage for users, eroding trust.

Networks like Astria or Espresso provide sequencing-as-a-service for multiple rollups. A bridge transaction must be included in a shared sequencer's block. If the sequencer set is compromised or colludes, it can perform double-spends across all connected rollups in a single coordinated attack, a scale of breach impossible in isolated monolithic chains.\n- Attack Vector: Cross-rollup double-spend via malicious sequencer.\n- Impact: Atomic failure across dozens of chains, not just one.

Many bridges, including Wormhole and Circle CCTP, rely on upgradeable contracts controlled by a multisig for emergency responses. A sovereign rollup, which settles to its own data availability layer, can fork itself and change its verification rules without the bridge governance's consent. This invalidates all bridge attestations, stranding assets.\n- Attack Vector: Sovereign chain hard fork that changes state validation.\n- Impact: Permanent asset stranding, zero recourse for bridge governance.

The only viable security model is for bridges to demand cryptographic proofs of the entire state transition, not just message attestation. This means verifying ZK proofs of execution, data availability proofs (like data availability sampling), and sequencer commitment proofs in a single bundle. Projects like Succinct and Polyhedra are pioneering this, but it requires 10x more on-chain verification gas.\n- Key Shift: Verify the chain's state, not just a signature about it.\n- Trade-off: Higher gas cost for unbreakable cryptographic security.

Monolithic bridges assume a single, secure execution environment. Modularity introduces shared sequencers (e.g., Espresso, Astria) that become a new, high-value target. A compromised sequencer can censor or reorder cross-chain messages, breaking atomicity and enabling MEV theft.

• New Trust Assumption: Security now depends on the sequencer set's liveness and honesty.
• Data Availability Risk: If the sequencer posts invalid state roots to a DA layer like Celestia or EigenDA, fraud proofs are your only recourse.

Bridges like LayerZero and Axelar rely on a canonical hub for finality. In a modular world, assets settle on specialized layers (e.g., Ethereum for security, Solana for speed). This fragments liquidity and security budgets.

• Capital Inefficiency: $10B+ TVL is now split across dozens of settlement layers, weakening each bridge's economic security.
• Finality Mismatch: Reconciling Ethereum's ~15m finality with a Solana VM rollup's ~400ms creates arbitrage and liveness attack vectors.

The transaction-based bridge model (push) breaks with modular latency. The future is intent-based (pull), where users declare a desired outcome and a solver network like UniswapX or CowSwap fulfills it across layers.

• Security Shift: Risk moves from bridge validators to solver competition and Across-style optimistic verification.
• Unified Liquidity: Solvers can tap into native AMBs, CEXs, and rollup bridges simultaneously, creating a ~$50B+ virtual liquidity pool.

You cannot have Trustlessness, Generalized Messaging, and Capital Efficiency simultaneously in a modular ecosystem. Existing bridges optimize for one, sacrificing others.

• LayerZero: Generalized but requires trusted off-chain oracle/relayer set.
• IBC: Trustless and capital efficient, but only for chains with fast finality.
• Wormhole: Generalizable with Circle CCTP integration, but relies on a 19-of-38 guardian multisig.