Carefully! Lots of text.
A blockchain bridge is a protocol that connects two blockchains and allows communication between them. For example, if you have bitcoins, but want to work on the Ethereum DeFi network, you can transfer assets using the bridge without selling your coins. These protocols are key to achieving interoperability in the blockchain space.
Introduction
Before talking about bridges, we need to consider the structure of the blockchain itself. Bitcoin, Ethereum, and BNB Smart Chain are some of the most common blockchain ecosystems that use different consensus protocols, programming languages, and system rules.
A bridge is a protocol that connects two blockchains with different economies and technologies so that they can interact with each other. These protocols connect separate ecosystems like a bridge between two islands.
Such bridges allow digital assets and data from one blockchain to interact with another blockchain, thereby ensuring their compatibility. Interoperability is a critical feature of the Internet, whereby devices around the world use the same set of open protocols to communicate with each other. This is why bridges play an important role in the blockchain space and enable convenient exchange of data and funds.
Why are blockchain bridges needed?
As blockchains emerged and developed, users encountered barriers that prevented them from transferring assets between different blockchains. Each of them operates according to certain rules and uses its own tokens, protocols and smart contracts. Blockchain bridges allow you to connect isolated ecosystems and create an interconnected network of blockchains with seamless exchange of tokens and data.
Bridges enable cross-chain transfers, open access to new protocols on other chains, and allow developers from different blockchain communities to collaborate with each other. In other words, bridges are the basis of interoperability in the blockchain industry.
How blockchain bridges work
Most often, bridges are used to transfer tokens. For example, let's say you want to move your Bitcoin (BTC) to the Ethereum network. To do this, you can sell BTC and then buy ETH, but you will then have to pay a transaction fee and possibly spend more due to price volatility.
The bridge allows you to transfer assets between networks without selling cryptocurrencies. To move 1 BTC to an Ethereum wallet, the bridge contract will lock your BTC and create an equivalent amount of Wrapped BTC (WBTC) - ERC20-standard wrapped tokens compatible with the Ethereum network. The transferred BTC amount will be locked in the smart contract, and equivalent tokens will be issued on the destination blockchain. A Wrapped token, or wrapped token, is a tokenized version of a cryptocurrency. It is tied to the value of the original asset and can usually be redeemed at any time.
To transfer, you only need to complete a few steps. For example, to use the Binance Bridge, you first need to select the source chain and specify the transfer amount, and then deposit the cryptocurrency to the address generated by the Binance Bridge. Binance Bridge will then send you the equivalent amount of wrapped tokens on the desired blockchain. To convert funds back, you need to perform the same steps, but in reverse order.
What types of blockchain bridges exist?
Bridges between blockchains can be categorized based on their functions, mechanisms, and levels of centralization.
Custodial and non-custodial bridges
One common classification is between custodial (centralized) and non-custodial (decentralized) bridges.
In custodial bridges, security is provided by a central authority. We recommend that you carefully review any service before transferring your assets to it.
Non-custodial bridges operate in a decentralized manner and manage the processes of blocking and mining cryptocurrencies using smart contracts, and therefore do not require the services of a bridge operator. In this case, the security of the system depends entirely on its code.
Blockchain bridges by function
Bridges can also be classified by function. For example, some of them may work with wrapped assets or sidechains.
Wrapped asset bridges provide cryptocurrency interoperability and allow, for example, the transfer of Bitcoin to the Ethereum network by turning BTC into Wrapped BTC (WBTC), an ERC20 wrapped token compatible with the Ethereum network. Sidechain bridges ensure compatibility and interaction between a parent blockchain and its child sidechain—a bridge should be used if they have different consensus mechanisms. An example of such a bridge is the xDai Bridge, which connects the Ethereum main network with the Gnosis Chain (formerly the xDai blockchain), an Ethereum-based payment sidechain. The security of xDai is ensured by a set of validators different from those maintained by the Ethereum network. The xDai Bridge allows you to easily transfer funds between these chains.
Blockchain bridges by mechanism
There are one-way (unidirectional) and two-way (bidirectional) bridges. One-way bridges transfer assets only to the destination blockchain, but not back to the native blockchain. Bidirectional bridges work in both directions.
Benefits of blockchain bridges
The most important advantage of blockchain bridges is compatibility.
They enable the exchange of tokens, assets and data between different blockchains, be they layer 1 and 2 protocols or sidechains. For example, WBTC allows Bitcoin users to explore the decentralized applications (Dapps) and DeFi services of the Ethereum ecosystem. Interoperability is critical to the future success of the blockchain space.
Another benefit of bridges is improved scalability. Some of them can handle a large number of transactions, thereby increasing efficiency. For example, the Ethereum-Polygon Bridge is a decentralized two-way bridge that works as a scaling solution for the Ethereum network. As a result, users can complete transactions faster and with lower fees.
Risks of blockchain bridges
Bridges between blockchains have their drawbacks. For example, attackers have already exploited vulnerabilities in their smart contracts to steal huge amounts of cryptocurrencies from cross-chain bridges.
Custodial bridges expose users to the risks associated with this storage method. Remember that a centralized organization managing a custodial bridge could theoretically steal user funds, so when using such solutions, give preference to well-known brands with a long history.
Another potential technical limitation is low throughput. Difficulties in scaling on a single chain can prevent large-scale blockchain interoperability.
While a bridge helps reduce network congestion, moving assets to another network does not solve the scalability issue as users will not always have access to the same set of Dapps and services. For example, some Dapps on Ethereum are not available on Polygon Bridge, limiting scalability.
Blockchain bridges also come with certain trust risks. Because bridges connect different blockchains, the overall security of interoperable networks depends on the least trusted party.
The future of blockchain bridges
The Internet has become a revolutionary system in part due to its high compatibility. Bridges between blockchains are key to increasing interoperability and popularity of the blockchain industry. They allow the exchange of assets between different protocols, which has already led to a number of innovations and an increase in the number of bridges, their users and transactions.
Most likely, the need for blockchain bridges will continue to grow as we move closer to the Web3 concept. In the future, the creators may be able to achieve greater scalability and efficiency for users and developers, and release solutions to address the security risks associated with bridges. Regardless, these protocols are fundamental to creating an interoperable, open, and decentralized blockchain space.
Summary
The blockchain industry is constantly changing and evolving. It operates not only popular protocols such as Bitcoin and Ethereum, but also many first and second level projects. The number of crypto coins and tokens is also growing exponentially.
Since each project operates within certain rules and technologies that may differ, bridges are needed to ensure compatibility between different blockchains. They connect ecosystem elements and provide opportunities for improved scale and efficiency. However, cross-chain networks are subject to numerous attacks, so work is now underway to create a more secure and reliable bridge.