What is a Blockchain Bridge?

It is difficult to imagine today's world without Web3 solutions, and the number of chains for which is growing. A blockchain bridge is a technology that allows transferring data, assets, and smart contracts between different blockchain networks. So today, together with Icon.Partners, we are diving into the topic of blockchain bridges on the web3. 

What Are Blockchain Bridges?

Definition and meaning of blockchain bridging

Blockchain bridging is the process of connecting different blockchains and enabling the transfer of information and assets between them. A specific smart contract is created that fixes the asset in the original network and creates a wrapped version of it in another network. The approach maintains the balance of assets and does not disrupt the system. 

The purpose of bridges in blockchain ecosystems

The main aim is to create interaction. Without bridges, users will have to endlessly convert assets through exchanges, which means extra costs and time. A bridge has the ability to transfer the value of an asset, access a smart contract, and expand the capabilities of decentralized applications. This means that an integrated Web3 ecosystem is being built. 

Blockchain bridge examples and use cases

Blockchain bridge examples include the well-known Wrapped Bitcoin, Polygon Bridge, Wormhole, Avalanche Bridge, and others.These bridges are reliable and popular and are used, in particular, to transfer assets between networks.

How Blockchain Bridges Work

The process of transferring assets between chains

Let's understand how blockchain bridges work. If it becomes necessary to transfer an asset from one network to another, that asset is blocked in the first network, and a specific copy, or equivalent, is created in the desired chain. And now the new asset is available for use. If the user needs to return the asset to the first network, the equivalent is destroyed and the original asset is unlocked. 

Smart contracts and interoperability mechanisms

The basis for the functioning of bridges is smart contracts, which perform actions to lock assets in the network, create duplicates of them, and then destroy them. Smart contracts interact with validators, oracles, and other entities that are necessary to confirm transfers between chains. 

Security challenges and risks in bridge design

Difficulties most often arise due to smart contract flaws, synchronization errors, false information from validators, etc. Blockchain bridges are part of a complex architecture, and because of this complexity, they are vulnerable to hacker attacks. 

Types of Blockchain Bridges

Trusted vs trustless bridges

Now let's look at different types of blockchain bridges. Trusted bridges rely on centralized platforms or intermediaries, and they guarantee the execution of actions between blockchains. The main thing is that users trust the parties to keep their assets safe. 

Trustless bridges operate on the basis of smart contracts and cryptographic protocols, thus eliminating human influence and reducing fraud. The disadvantage of trustless bridges is that they require thorough code auditing to prevent errors and vulnerabilities. 

Unidirectional and bidirectional bridges

Unidirectional bridges transmit information and assets in only one direction, from network to network, but without any return traffic. Bidirectional bridges are more convenient because they allow for mutual exchange between chains. This increases user-friendliness, but the development of such bridges is much more complex and the bridges themselves require a higher level of security. 

Cross-chain bridges vs layer-2 solutions

Cross-chain bridges create a connection between two different chain systems and allow assets to be transferred between them. In contrast, layer-2 solutions work on a single blockchain and increase its speed and scalability. The difference is that bridges connect different systems, while layer-2 solutions optimize the chain without changing its base. 

Building and Auditing Blockchain Bridges 

How to build a blockchain bridge — core components

Now let's look at how to build a blockchain bridge. The key is to create a mechanism for locking an asset in the primary chain and creating its equivalent in the target network. Smart contracts, validators, verification protocols, and asset management systems are most commonly used. 

Importance of blockchain bridge audits

Blockchain bridge audits are a key element of security compliance, as the vast majority of attacks are related to vulnerabilities in smart contracts. Independent auditors evaluate code and protocol security, test the system for resistance to attacks, and identify weaknesses and problem areas. 

Common vulnerabilities and how audits prevent exploits

Typical bridge vulnerabilities include incorrect signature verification, transaction confirmation errors, incorrect chain synchronization, etc. Problems can also arise from central control over validators. Auditors check each type of risk manually or automatically, applying hacking scenarios and various types of attacks to identify security gaps and change them. 

Popular Blockchain Bridges 

Overview of well-known blockchain bridges list

We have already talked a little about blockchain bridges list earlier, mentioning Polygon Bridge, Wormhole, Avalanche Bridge, Arbitrum Bridge, and Binance Bridge. They create a connection between primary networks and allow assets to be exchanged between networks without involving intermediaries. First and foremost, this is aimed at interaction and expansion of the Web3 network.

Examples: Polygon Bridge, Wormhole, Avalanche Bridge

Polygon Bridge connects the Polygon and Ethereum networks and helps transfer assets between them. Wormhole works with more than 10 networks and allows asset exchange, including with Ethereum and Solana. Avalanche Bridge is known for its speed and low usage costs. 

Lessons learned from past bridge hacks

The largest and most significant blockchain bridge hacks, such as the Ronin Bridge or BNB Bridge hacks, highlight the importance of auditing and security. The main points are the need to avoid centralized keys, to constantly test and create multi-level protection and verification schemes. 

FAQ on Blockchain Bridges 

What is a blockchain bridge?

These are tools that connect blockchains to each other for the transfer of assets. 

How do blockchain bridges work?

The bridge freezes the asset in one network and creates its counterpart in another. When the asset returns to the first network, the counterpart is destroyed.

What are the main types of blockchain bridges?

The division is based on key characteristics, such as whether bridges can transfer assets in both directions between networks or only in one direction, etc.  

Why are blockchain bridge audits important?

The audit of blockchain bridges allows you to identify weaknesses, errors, and inaccuracies, the elimination of which prevents network crashes and hacks. 

How can developers build secure blockchain bridges?

It is worth examining the experience of past hacks, anticipating possible scenarios, and conducting an audit to protect users and the network.