How Stellar Reaches Agreement Without Mining or Staking @StellarOrg runs its native asset on the Stellar Consensus Protocol (SCP), first introduced in 2015 by David Mazières (@dmazieres). Maz
@StellarOrg runs its native asset on the Stellar Consensus Protocol (SCP), first introduced in 2015 by David Mazières (@dmazieres). Mazières is a professor of Computer Science at Stanford University and serves as Chief Scientist at the Stellar Development Foundation.
Unlike proof-of-work or proof-of-stake networks, Stellar has no miners or stakers. Instead, SCP is built on federated Byzantine agreement (FBA), a model that gives each participant individual control over whom to trust. Each validator publishes a list of other nodes it relies on and sets a threshold for how many of them must agree before a decision is accepted. Any group that clears that threshold is called a quorum slice.
SCP allows decentralized, leaderless networks to reach a consensus outcome efficiently, with overlapping trust lists binding the network together in a way that resembles how internet service providers peer with one another. As long as those trust lists share sufficient overlap, the network reaches agreement safely.
The protocol is designed with a deliberate trade-off: if trust lists fail to overlap enough, the network halts rather than risks producing conflicting transaction histories. That design was tested in practice on May 15, 2019. At 1:14 p.m. Pacific time, the Stellar network halted for 67 minutes due to an inability to reach consensus. During that time no ledgers were closed and no transactions were processed.
The ledger state remained safe and consistent across the network, and no one lost their funds. The Stellar Development Foundation explained in its post-mortem that "some new nodes took on too much consensus responsibility too soon," disrupting the quorum overlap the network depended on.
The SDF noted that the halt was not a failure of the consensus protocol itself, but rather that a temporary halt is preferable to the permanent confusion of a fork. The incident highlighted both the resilience of SCP's safety guarantees and the operational discipline required to expand a federated validator set responsibly.
Sources:Stellar Development Foundation: May 15th Network Halt (Official Post-Mortem)Stellar Development Foundation: Stellar Consensus Protocol Whitepaper AnnouncementCoinTelegraph: Stellar's Blockchain Briefly Goes Offline (May 2019)
