Ethereum and Solana are separate blockchains. They don't share state, don't share a mempool, and have no native awareness of each other. An asset on Ethereum — ETH, for instance — doesn't exist on Solana. The two networks are, in the strictest sense, isolated.
This creates a practical problem. Users hold assets on one chain and want to use applications on another. A protocol deployed only on Solana is inaccessible to someone whose capital sits in Ethereum smart contracts. The multi-chain world, which is the current state of crypto, creates constant demand for moving value and information across these isolated environments.
A blockchain bridge is a system that enables this movement. The word "bridge" is intuitive — it connects two separate things. But the mechanism behind it is worth understanding carefully, because bridges have become one of the most exploited categories of infrastructure in crypto. How a bridge works determines how much you can trust it.
How Bridges Work
The fundamental problem a bridge solves is this: you can't just teleport an asset from one chain to another. Blockchain A doesn't send messages to Blockchain B. Each chain's validators only observe their own chain's history.
Bridges solve this by using a lock-and-mint or burn-and-mint model. Here's the basic lock-and-mint flow:
- A user deposits ETH into a smart contract on Ethereum. The contract locks those funds.
- A bridge operator (or a network of operators) observes this deposit on Ethereum and triggers an action on the destination chain.
- On the destination chain — say, Solana — a corresponding amount of "wrapped ETH" (wETH on Solana) is minted and sent to the user's address.
The user now holds a synthetic representation of their ETH on Solana. When they want their original ETH back, they reverse the process: burn the wrapped tokens on Solana, and the bridge releases the locked ETH on Ethereum.
The locked funds on the source chain are the collateral backing all outstanding wrapped tokens on the destination chain. If that lockbox is compromised, the wrapped tokens become unbacked.
Liquidity pool bridges operate differently. Instead of locking and minting, they maintain pools of native assets on both sides. When you bridge ETH from Ethereum to Arbitrum, a liquidity pool model might transfer from an Ethereum-side pool to an Arbitrum-side pool, giving you native ETH (not a wrapped version) on the destination chain. This avoids the wrapping complexity but requires sufficient liquidity on both sides at all times.
Native bridges are built directly by layer-2 networks to connect to Ethereum. Arbitrum's official bridge, Optimism's bridge, Base's bridge — these are controlled by the rollup operators and use the rollup's own security guarantees rather than a separate bridge protocol. They're generally considered more secure but often slower (withdrawal periods of 7 days are standard for optimistic rollups due to the fraud proof window).
Third-party bridges like Across, Stargate, and Hop Protocol offer faster speeds and more chain coverage by taking on more complex liquidity management, often with their own token economics and risk assumptions.
Where the Constraints Live
Bridges concentrate risk in ways that most DeFi protocols don't.
The core issue: a bridge's locked fund contract holds the collateral for every wrapped token it has ever issued. At peak usage, major bridges hold hundreds of millions to billions of dollars in a single smart contract. This makes them high-value targets. A vulnerability in the bridge contract — or in the off-chain system that monitors deposits and triggers mints — can drain the entire lockbox at once.
The three largest crypto hacks on record, as of 2025, are all bridge exploits: Ronin Network ($625M, March 2022), Wormhole ($320M, February 2022), and Nomad ($190M, August 2022). In each case, the attacker either compromised the signing keys authorizing mints, exploited a contract vulnerability, or both. The combination of large locked balances and complex cross-chain logic creates a difficult-to-audit attack surface.
Trust assumptions vary significantly by design. A bridge secured by five multisig signers — even if they're known entities — carries fundamentally different trust assumptions than one secured by a decentralized validator network or one that inherits Ethereum's security directly. Understanding which type you're using matters.
Finality mismatch is a subtler issue. Different chains reach finality at different speeds. A bridge that mints on the destination chain before the source-chain deposit is truly finalized can, in theory, be exploited by blockchain reorganizations — reversing the deposit on the source chain after the minted tokens have already been distributed. Production bridges handle this by waiting for sufficient confirmations, but it adds latency.
What's Changing
Bridge infrastructure is maturing, driven largely by the lessons from 2022's exploit wave.
The main structural shift is toward light-client based verification. Traditional bridges relied on trusted validator sets or multisigs to attest that deposits happened. Light-client bridges use cryptographic proofs — the destination chain doesn't need to trust anyone's word that a deposit occurred; it verifies the proof directly. This is harder to build but eliminates the trusted-signer attack surface. The IBC protocol (used by Cosmos) pioneered this approach; newer projects are extending similar designs to EVM chains.
Zero-knowledge proofs are enabling another approach: bridges that generate a ZK proof of the source chain's state, which the destination chain can verify trustlessly. This is computationally expensive today but getting cheaper, and several teams are actively building toward it.
Layer-2 native bridges continue to be the recommended path for Ethereum-to-L2 movement specifically because they inherit the rollup's security model. For cross-L1 movement (Ethereum to Solana, for instance), trust-minimized solutions remain an active area without a settled best practice.
Confirmation Signals
Watch for: light-client or ZK-proof based bridge designs achieving significant TVL without exploits over multi-year periods. Reduction in the percentage of total DeFi losses attributable to bridge exploits as more secure architectures gain adoption. Native bridge withdrawal times decreasing on optimistic rollups as fraud proof mechanisms become faster.
Invalidation Criteria
The bridge category as currently designed would face systemic pressure if: ZK proving infrastructure failed to become cheap enough for production-grade bridge use; if regulatory prohibitions made cross-chain movement legally restricted in major jurisdictions; or if a widely trusted "secure" bridge design suffered a large exploit, resetting the field's confidence in trust-minimized approaches.
Timing Perspective
Now: Bridges are in active use and carry real risk. Anyone moving assets cross-chain should understand which bridge model they're using and its trust assumptions. Native L2 bridges are the default recommendation for Ethereum-to-L2 movement despite withdrawal delays.
Next: Light-client and ZK-based bridges are transitioning from research to early production. This is the meaningful architectural evolution to track over the next two to three years.
Later: A world where cross-chain interoperability is as trust-minimized as same-chain interaction is theoretically achievable, but it requires cryptographic infrastructure that's still being built.
Boundary Statement
This explanation covers the bridge mechanism and its security surface. It doesn't address individual bridge protocols' specific implementations, token rewards, or fee structures. Whether any particular bridge is appropriate for a given transaction depends on the amount, urgency, and destination chain — considerations outside this scope.
Bridges are not uniformly risky, nor are they uniformly safe. The design determines the trust model, and the trust model determines the risk. That's the useful frame.
