What are blockchain bridges?

A blockchain bridge is a protocol connecting two distinct blockchains to enable the transfer of digital assets and information between them. Blockchains generally operate in isolated environments. A blockchain like Bitcoin has its own rules, consensus mechanism, and native cryptocurrency. It cannot natively communicate with another network like Ethereum. As the cryptocurrency ecosystem grew, the need for these separate networks to interact became apparent. Blockchain bridges were developed to solve this lack of interoperability, allowing users to move assets from one ecosystem to another.

Without bridges, moving assets between blockchains usually requires the use of a centralized exchange. For instance, if a user wanted to move funds from the Bitcoin network to Ethereum, they would traditionally have to send their bitcoin to a centralized exchange, sell it for ether, and then withdraw the ether to an Ethereum wallet. This process involves multiple steps and incurs various transaction fees.

Bridges aim to streamline this by allowing users to transfer value directly between networks. This interoperability gives users access to decentralized finance (DeFi) protocols, decentralized applications (dapps), and different blockchain features that might not be available on their original network.

Most blockchain bridges do not physically move a cryptocurrency from one network to another. Instead, they use a "lock and mint" or "burn and release" mechanism.

When a user wants to bridge an asset, they send their funds to a smart contract on the original blockchain, which locks those assets. The bridge protocol then verifies this and mints an equivalent amount of a representative token on the destination blockchain. These representative tokens are often called wrapped tokens. For example, Wrapped Bitcoin (WBTC) is an ERC-20 token on the Ethereum network that represents Bitcoin locked on the original Bitcoin blockchain.

When the user wants to return to the original network, they send the wrapped tokens back to the bridge on the destination chain, where the tokens are "burned" or destroyed. The smart contract on the original chain then unlocks and releases the original assets back to the user.

Bridges can generally be categorized into two main types based on how they are secured and operated: trusted (centralized) and trustless (decentralized).

While blockchain bridges provide valuable interoperability, they introduce significant risks that users should be aware of.

One of the primary concerns is security. Because bridges often hold large amounts of locked assets in smart contracts to back the wrapped tokens, they become attractive targets for bad actors. If there is a flaw or vulnerability in the bridge's code, those locked funds can be compromised. The cryptocurrency space has seen several high-profile security incidents where bridges experienced unauthorized access, resulting in a substantial loss of funds.

Additionally, trusted bridges carry centralization risks. If the centralized entity controlling the locked assets acts maliciously, goes offline, or faces regulatory action, the wrapped tokens on the destination chain could lose their backing and become essentially worthless. Because of these factors, it is important to research a bridge's security audits and operational model before using it.

Disclosures:

Content provided for educational purposes only. Not investment advice or a recommendation. Trading and owning digital assets involves significant risk, including the risk of substantial loss. Cryptocurrency services are offered through an account with Robinhood Crypto, LLC (NMLS ID 1702840). Robinhood Crypto is licensed to engage in virtual currency business activity by the New York State Department of Financial Services. Cryptocurrency held through Robinhood Crypto is not FDIC insured or SIPC protected.