ICP CONSENSUS — HOW AGREEMENT IS REACHED

ICP uses a novel consensus protocol called IC-Consensus. It combines several innovations:

1. THRESHOLD BLS SIGNATURES

Each block proposal is signed by threshold BLS. If enough nodes agree, the block is finalized. This is faster than traditional Nakamoto consensus.

2. ASYNCHRONOUS VERIFIABLE RANDOM FUNCTION (AVRF)

Randomly selects block makers each round. Prevents targeted attacks on specific nodes. Ensures fairness.

3. PIVOTING

If a block maker is slow or malicious, another node takes over. The network dynamically switches to the fastest honest proposer.

4. DAG-BASED CONSENSUS

Instead of a simple chain, ICP uses a directed acyclic graph. Multiple blocks can be proposed in parallel. This increases throughput dramatically.

5. INTER-SUBNET ROUTING

The NNS coordinates messages between subnets. When canister A on subnet 1 calls canister B on subnet 2, the message is routed through a dedicated protocol.

FINALITY:

ICP achieves FINALITY in two steps:

- Verification: A block is verified once enough threshold signatures are collected

- Finalization: A block is finalized when it reaches a certain number of confirmations

This is different from Bitcoin where finality requires 6 confirmations. ICP finality is near-instant.

Next: Part 5 — Subnets and Replication

$ICP #InternetComputer #Course