The Stellar white paper "presents federated Byzantine agreement (FBA), a model suitable for worldwide consensus." It then goes on to state that it "further presents the Stellar consensus protocol (SCP), a construction for FBA." When reading the paper, I fail to identify the point at which it is no longer FBA that is described but SCP. My interpretation of the wording is that FBA is part of SCP but not all that is SCP is FBA. So -- what differentiates the two terms? Where to draw the line?


The Stellar Consensus Protocol is a type of federated Byzantine agreement protocol. So FBA is a broader category that includes SCP.

There's a more recent peer-reviewed paper written for the SOSP that I personally find a bit easier to parse than the original white paper. Here's what it says:

"Stellar introduces a new Byzantine agreement protocol, SCP (Stellar Consensus Protocol), through which token issuers designate specific validator servers to enforce transaction finality."

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  • Hi Justin, thank you. I agree with you, I also find the SOSP paper easier to digest. It has also been my intuition that FBA is a protocol of which SCP is one instance. However, and that was my original question, which parts described in those papers apply to FBA in general, and which are specific to SCP? Please apologize if this was not clear from how I worded the original question. – blockrookie Jul 9 at 9:43
  • Got it! In the SOSP paper, I think section 3.1 Federated Byzantine agreement covers FBA generally. Section 3.2 Protocol description switches to talking about SCP specifically. Does that make sense? – Justin Rice Jul 10 at 11:55

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