Consensus on Metal Blockchain
In this article we will explore why the Metal Blockchain employs Avalanche protocols as the latest advancement in consensus technology.
Welcome to our deep dive series on the Metal Blockchain!
In this series, we will be taking an in-depth look at the various components and features of the Metal Blockchain. We will explain the Layer 0 concept, explore the history of consensus mechanisms, and why the Metal Blockchain employs Avalanche protocols as the latest advancement in consensus technology.
We’ll also take an in-depth look at the flow of a single blockchain on the Metal Blockchain, the underlying components, such as the Virtual Machine, Subnets, and the $METAL token, including its tokenomics, fee burns, fee schedule, and staking rewards.
This series aims to provide a comprehensive understanding of the Metal Blockchain for both experienced and new users. Join us as we delve into the technical details and discover the unique advantages of the Metal Blockchain.
In the fourth article of our deep dive series, we will examine the history of consensus mechanisms and explore why the Metal Blockchain employs Avalanche protocols as the latest advancement in consensus technology.
What is a consensus mechanism?
A consensus mechanism is a process or algorithm used to achieve agreement among the members of a distributed network. In a blockchain system, the consensus mechanism is used to determine which transactions will be added to the blockchain and in what order. This is an essential component of a blockchain system, as it ensures the integrity and consistency of the distributed ledger.
Consensus is the process by which a group of independent nodes, often called "validators," come to an agreement on a decision. This ensures that the network has a synchronized view of the data, known as the "state." Without consensus, it is impossible to guarantee that the state one validator believes to be true will be shared by all other nodes in the network.
Proof-of-Work (PoW) and Proof-of-Stake (PoS) are often confused with consensus protocols, but they are actually Sybil control mechanisms. PoS alone does not achieve consensus; it must be coupled with a protocol, such as Practical Byzantine Fault Tolerance (PBFT), Tendermint/Cosmos, or Snowman, to make decisions.
Similarly, PoW alone is not a consensus mechanism; in systems like Bitcoin, it is used in conjunction with the "longest chain" rule to achieve consensus.
Three approaches to Consensus in the past 45 years
Over the past 45 years, there have only been three approaches to the consensus problem in distributed systems: classical, Nakamoto, and Avalanche. Classical consensus protocols, such as PBFT, are based on the assumption that all nodes are trustworthy and operate correctly.
The Nakamoto consensus, exemplified by Proof-of-Work (PoW), is based on the assumption that a majority of nodes are honest, but some may be malicious.
In the next sections, we will compare and contrast the Nakamoto and Avalanche consensus protocols. Both of these protocols are used in blockchain systems to achieve agreement among the network participants, but they differ in terms of their underlying assumptions, their performance characteristics, and the costs and benefits associated with their use.
The Nakamoto Consensus
The first major breakthrough in consensus protocols was the development of Nakamoto consensus protocols, which became popular with the rise of Bitcoin. These protocols do away with the need for all-to-all communication, making them a natural fit for open, permissionless settings where any node can join the network at any time.
Unlike classical consensus protocols, Nakamoto consensus provides a probabilistic rather than deterministic safety guarantee. A protocol parameter can be used to make the probability of a double spend arbitrarily small, enabling the construction of high-value financial systems on this foundation.
However, Nakamoto-based consensus protocols are costly, wasteful, and limited in performance. They require computations that consume large amounts of energy, and according to the International Energy Agency, cryptocurrency mining uses at least as much energy as the entire nation of Ireland.
As a result, these systems constantly leak value from their ecosystems to power companies. To maintain the security of proof-of-work systems, the miners can never be switched off, meaning that this energy consumption will continue indefinitely.
Mining a block is difficult by design, so Nakamoto protocols take a long time to finalize transactions - it can take up to an hour for a Bitcoin transaction to become final. This low latency will not improve even as technology advances.
The Avalanche Consensus
Avalanche consensus protocols represent the next major breakthrough in consensus technology, combining the benefits of Nakamoto consensus (robustness, scalability, and decentralization) with the benefits of classical consensus (speed, quick finality, and energy efficiency).
Protocols in the Avalanche family operate through a process of repeated sub-sampled voting. When a validator is trying to determine whether a transaction should be accepted or rejected, it asks a small, random subset of other validators whether they think the transaction is valid. If the validator that is queried thinks the transaction is invalid, has already rejected the transaction, or prefers a conflicting transaction, it replies that it thinks the transaction should be rejected. Otherwise, it replies that it thinks the transaction should be accepted.
If a sufficiently large portion (alpha α) of the validators sampled reply that they think the transaction should be accepted, the querying validator prefers to accept the transaction. That is when it is queried about the transaction in the future, it will reply that it thinks the transaction should be accepted. Similarly, the validator will prefer to reject the transaction if a sufficiently large portion of the validators replies that they think the transaction should be rejected.
The validator repeats this sampling process until the alpha of the validators queried reply the same way (accept or reject) for beta β consecutive rounds.
In the common case when a transaction has no conflicts, finalization happens quickly. When conflicts do exist, honest validators quickly cluster around conflicting transactions, entering a positive feedback loop until all correct validators prefer the same transaction. This leads to the acceptance of non-conflicting transactions and the rejection of conflicting transactions.
It is highly likely (based on the system parameters) that if any honest validator accepts or rejects a transaction, all honest validators will eventually do the same. This guarantee is important for ensuring the consistency and integrity of the blockchain. By using the sub-sampled voting process described above, the protocol is able to reach consensus among the validators in a way that is robust, efficient, and resistant to adversarial behavior.
Why Metal Blockchain Adopts the Avalanche Consensus
Metal Blockchain utilizes the Avalanche consensus protocol (Avalanche & Snowman) since it is designed to be scalable, robust, sustainable and decentralized. It has low latency and high throughput, making it suitable for a wide range of applications. Additionally, it is energy efficient and does not require specialized computer hardware. It is also designed to perform well in adversarial conditions and is resistant to "51% attacks."
The Metal Blockchain however offers a 80% parameterization. This means that in order to initiate a hard fork on the network, a significant 81% validator dominance is required. This approach provides increased confidence and comfort for enterprises and institutions, ensuring a more stable and controlled environment for blockchain governance and updates.
The number of messages that each node has to handle per decision is O(k), and it does not grow as the network scales up, allowing it to scale to millions of validators participating in consensus and achieving truly global scale decentralization for permissionless blockchain systems.
Snowman Consensus Protocol
Snowman is a variant and family member of the Avalanche consensus protocol that operates in a linear manner. The key distinction is that each vertex in Snowman can only have a single parent and a single child, unlike in a Directed Acyclic Graph (DAG) structure like the X-Chain. To learn more about the DAG structure, check out our documentation.
Snowman is a high-throughput, totally ordered consensus protocol that is optimized for use on blockchain systems. It is powered by the Avalanche consensus protocol and is well-suited for implementing smart contracts.
The X-Chain, currently utilizes the Avalanche Consensus Protocol. However, it will transition to the Snow Consensus Protocol in the future.
Similarly, the P-Chain (Platform) and C-Chain (EVM) on the Metal Blockchain implement the Snowman consensus protocol. Additionally, the A-Chain (Proton) on the Metal Blockchain will adopt and implement the Snowman consensus protocol. Any Subnet will also implement the Snowman consensus by default.
We have comprehensive technical documentation available that provides further detailed information about consensus on Metal Blockchain.
In the following article, we will provide an overview of the decentralized governance model employed on the Metal Blockchain and the three key entities it encompasses: Validators, Delegators, and the Metal Foundation, shedding light on their respective roles and contributions.