Blockchain bridges 101: trusted and trustless

GM everyone! Let’s get back to Web3 basics and recall the difference between 2 types of blockchain bridge systems.

🌉What is a bridge? A blockchain bridge enables communication between various types of blockchains. Without these bridges, it's essentially impossible due to differing rules and consensus mechanisms.

Bridges allow to:
1️⃣Transfer data between different blockchains - for example, BNB Chain and Ethereum.
2️⃣Transfer data between different layers - for example, Ethereum (L1) and Polygon (L2)

There are 2 types of bridge implementations:

🟢Trusted bridges - have some third party between blockchains, who holds the custody of the assets. This method provides speed and efficiency.

The primary issue here is that this kind of bridge has a vulnerability: if the custodian is hacked or compromised, it can disrupt all blockchain operations.

🔵Trustless bridges - act without any sort of regulator or custodian. Instead, they use cryptographic proofs and smart contracts. This is a more decentralized version of bridge technology, which doesn’t have a single point of failure (custodian or regulator).

The tradeoff is that they involve greater technical complexity and are frequently targeted by hackers seeking to exploit vulnerabilities and siphon off the bridge's assets. Because of that, trustless bridges are considered to be less safe from outside attacks, if the smart contract’s code isn’t fully audited.