Stellar used to implement Ripple’s consensus algorithm, but recently they started using their own consensus protocol called Stellar Consensus Protocol or SCP.
SCP is an FBA (Federated Byzantine Agreement) protocol that guarantees that its well-behaved nodes can sustain the network despite the presence of malicious nodes. This means that it is Byzantine Fault Tolerant. The way the SCP achieves this and the core idea behind it is Federated voting.
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