From Trust to Consensus: How Stellar Reaches Agreement Without Mining

Consensus is what keeps Stellar’s decentralized payment network secure and synchronized. Instead of one central authority approving transactions, many independent nodes (validators) agree on the same version of the ledger. This prevents double-spending and ensures reliability.

Why SCP?

Unlike Proof of Work (Bitcoin) or Proof of Stake (Ethereum and others), Stellar’s SCP is based on Federated Byzantine Agreement (FBA). Each validator chooses a set of other validators it trusts (its quorum set). Agreement emerges when these trust choices overlap, giving SCP its open and decentralized nature.

1. No mining.
2. No staking.
3. Just trust-based agreement.

Key Terms

• Quorum set → The list of nodes a validator trusts.
• Threshold → Minimum number of nodes in that set that must agree.
• Quorum slice → A smaller subset of the quorum set that’s enough to reach agreement.
• Federated voting → Validators move from voting → accepting → confirming a statement.
• Safety vs Liveness → SCP prioritizes safety (no conflicting ledgers) over liveness (progress may pause until consensus is reached).

How SCP Reaches Agreement

1. Nomination → Nodes propose transaction sets. Over time, they converge on the same candidate set.
2. Ballot protocol → Validators vote, prepare, and commit that candidate set until the network locks in a single, agreed ledger.

Why It Stands Out

• Fast & energy-efficient → No mining required.
• Decentralized trust → Each node defines who it trusts.
• Resilient → Safety is guaranteed as long as quorum sets overlap correctly.

Takeaway

SCP is Stellar’s way of achieving global agreement without mining or staking. It’s lightweight, secure, and designed for payments. The trick is in quorum design: overlap ensures safety and keeps the network moving forward.

Next time you hear “consensus,” remember: on Stellar, it’s all about trust + overlap. That’s SCP in a nutshell.