Interoperability

Interoperability is about two or more blockchains interacting to move assets and data back and forth. This is usually achieved by two-way mechanisms called bridges.

Interoperating chains can be in a symmetric or an asymmetric relationship. Two main chains that interoperate (Ethereum and Cardano, for instance) form the symmetric case. A mainchain and a sidechain that interoperate form the asymmetric case.

In the symmetric case, if one chain dies, the other one is not affected. The situation is different with the asymmetric case, because the sidechain depends on the mainchain, but not the other way around. If the sidechain dies or is compromised, a firewall property typically protects the mainchain from harm. However, if the mainchain is compromised, the sidechain will usually no longer be able to function securely. However, the precise consequences depend on the nature of the sidechain's dependency on the mainchain.

The main blockchain and its properties (like throughput and scaling) represent layer 1. Sidechains and off-chain solutions (like ZK-rollups) that run independently alongside the main blockchain are referred to as layer 2 solutions.