Transferring assets from one blockchain to another might seem like an easy task to accomplish on the surface. Indeed, a user will see nothing more than a wallet, the choice of a network, and a confirmation button. Yet, two separate blockchain systems have to interact somehow despite being built with entirely different technology. Ethereum, Solana, and other blockchains do not share the same blockchain ledger, so an asset cannot be moved between them just like a payment between accounts on the same network.
That is what cross-chain systems help to achieve via the creation of special mechanisms that help represent assets on another blockchain. For example, some bridges lock the assets on one network and mint them on another one. Some solutions use the burn-and-mint principle or even different cross-chain messaging systems.
What should be noted, however, is that an asset will not physically move from one blockchain to another. Instead, it is an information of its existence that gets verified and represented. It is easy to forget about it due to modern wallets' design.
But the greater issue at stake is trust. The destination blockchain must somehow have the means of knowing that the alleged transaction actually took place on the source blockchain.
Every cross-chain design has its own method for doing this, with some using validators, multi-signature solutions, oracle services, or any other external component, while others try to validate the information from another blockchain in some way. All of them have their own underlying security model.
A vulnerability in a smart contract poses a threat, but an external operator may pose extra trust issues too. The risks of smart contract, technological, counterparty, and risks of wrapped tokens on Ethereum have all been documented.
This is the reason why the bridge should never be evaluated by mere token transfer speed or user experience interface alone. The security of the bridge rests upon the entire architecture behind it – the smart contracts, the validation mechanism, the operators, relayers, and the blockchains themselves.
This is also because interoperability is becoming a bigger infrastructure challenge than a bridge one. For instance, protocols like IBC were created to support authenticated communication between independent distributed ledgers.
While previously these technologies only thought about token transfers, now they think about how the blockchains can exchange their verified data and messages. This might potentially reduce application dependency on isolated ecosystems.
However, even with that interoperability will face different levels of security, transaction finality, fees, liquidity, software and governance in different networks.
From my point of view, this is the thing which should have much more attention. While user sees a simple transfer of funds, there might be a complex process of verification and interaction behind this action.
When blockchain networks start growing in number, the connection of them might become an equally important process to the creation of the networks themselves. The real idea of the whole thing should not be just in the ability to send funds to anywhere. It should be about making the interaction between different blockchains reliable enough for the user to forget about all technical details of this process.
