Hello reader... Here is a homework on Consensus Algorithm for @alphafx.
The consensus algorithm is a set of codes that enables nodes on a network to agree and confirm transactions. The Stellar Consensus Protocol is as type of Algorithm system that enables transactions to be confirmed on the stellar network.
The stellar network is a network designed to ensure a secure and fast financial transactions across borders internationally. It is a blockchain based open ledger that supports transactions of valuable assets virtually across countries within a short period of time.
The stellar network was developed by the Stellar Development Foundation in 2014. The original cryptocurrency on the network is called Lumen (XLM). The network makes use of a very different algorithm protocol created by a Stanford professor, David Mazières. This protocol is known as the Stellar Consensus Protocol (SCP).
As David explained in the Stellar white paper, the consensus protocol is designed to satisfy four main functions. Namely; Decentralized Control, Low Latency, Flexible Trust and Asymptotic Security. These four functions is known to be found in different already existing protocols, but not all in one. Bringing all in one is the special feature of SCP as a customized hybrid algorithm.
Decentralized Control - Stellar is a network that is open to anyone to participated. The concept of decentralization is to make the control and decision making power remain with the participants of the network. With this no central authority or third party controls the network.
Low Latency - Stellar was designed for bulk and ultrafast transactions. The SCP enable nodes come to consensus within a very short period; seconds. This supports the confirmation of a transactions in 3 - 5 seconds.
Flexible Trust - On the Stellar network, every node can choose what set of nodes to trust. Thus, not all nodes needs to agree before consensus is achieved. This also give room for the network to function even in the presence of node failures. This helps to keep the network in check.
Asymptotic security - The Stellar network provides a concrete cryptographic security to work against adversaries even if they posses high computing power.
| Mechanism | Decentralized Control | Low Latency | Flexible Trust | Asymptotic Security |
|---|---|---|---|---|
| Proof of work | ✓ | |||
| Proof o Stake | ✓ | maybe | maybe | |
| Byzantine Agreement | ✓ | ✓ | ✓ | |
| Tendermint | ✓ | ✓ | ✓ | |
| SCP (FBAS) | ✓ | ✓ | ✓ | ✓ |
Source : Stellar White paper
The Federated Byzantine Agreement System (FBAS)
The SCP works by a Federated Byzantine Agreement System. This is a system that have a list of nodes to agree and come to consensus about a value. The traditional Byzantine Agreement System makes use of a centralize authority to add trustable participants to the the the list of nodes that make consensus. In contrast, SCP is a open network that allows anyone to participate in consensus.
So how can Consensus be achieved with a global number of participants; here we need to understand the term Quorum and Quorum Slice
- A Quorum is a set of nodes that is sufficient to make an agreement while a Quorum Slice is a subset of a Quorum. A Quorum may contain more than one slice but for it to come to a consensus there has to be a mechanism called Quorum Intersection. This intersection brings two or more slices together on agreement. For an intersection to occur the slices must have at least a node in common that links them up.
Federated Voting
The Federated Byzantine Agreement System uses a federated Voting technique to achieve consensus or agree on a statement. This technique involves exchange of messages between nodes and ending with an outcome. A round of federated voting involves three phases: Unknown, Accepted and Confirmed
Unknown is the starting phase of the federated voting at which the status of a statement is unknown to the network. However, the statement is voted by a node N and broadcasted to other nodes. When the statement has received enough necessary votes from the quorum, then the statement is said to be Ratified. A Ratified statement can then move to the next stage, Accepting.
Accepting a statement secures a stronger guarantee. When the node N accepts a statement, no other node in the network will ever accept a contradictory statement. This shows that even when a node unawarely voted a contradictory statement, it can agree with the quorum by accepting the statement.
Accepting a value can only be contradicted by a blocking set. A blocking set is a set that contains a node from each intersecting quorum slice of node N. The blocking set does not make a Quorum but can accept a contradictory statement. This makes other nodes accept the contradictory statement. Hence for consensus to be achieved node N have to concur with the blocking set as well as the rest of the quorum.
- The node N confirms the statement accepted by the rest of the quorum and brings the voting to an end.
Safety and Liveness
The Stellar Consensus Protocol Guarantees two important properties of a consensus system: Safety and Liveness
Safety: The FBAS ensures that no two nodes in a quorum externalise different values for the same slot. That is the system ensure that the same outcome is produced for all nodes in the quorum
Liveness: The FBAS ensures the network continues to achieve consensus even in the presence of failed or ill-behaved nodes.
Conclusion
The Stellar network used the SCP to confirm transactions, create blocks and add them to the blockchain. The SCP is so effective as it support Decentralized Control, Low latency, Asymptotic security and Liveness.
Thank you
@alphafx
Best Regards!!
task well done. was missing in proper comparison and pros and cons.
Thanks for participating
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