From aeb7c724e189b59c8fa9fa4a4c17cd6d74df9442 Mon Sep 17 00:00:00 2001 From: Goodnessukaigwe Date: Tue, 15 Apr 2025 01:59:51 +0100 Subject: [PATCH] chore: add Ethereum consensus mechanisms documentation --- Answer/session_5_answer.md | 140 +++++++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) create mode 100644 Answer/session_5_answer.md diff --git a/Answer/session_5_answer.md b/Answer/session_5_answer.md new file mode 100644 index 0000000..d5ea73f --- /dev/null +++ b/Answer/session_5_answer.md @@ -0,0 +1,140 @@ +# Ethereum Consensus Mechanisms +### What is Etherum consensus mechanism +Ethereum’s consensus mechanism(**Proof of Stake (PoS)**) is how the network agrees on the state of the blockchain without needing massive energy use. It replaced the old **Proof of Work (PoW)** system during **The Merge** in September 2022, shifting from miners and energy-heavy computations to validators and economic incentives. + +In PoS, **validators** are chosen to create and confirm new blocks. To become one, you must **stake 32 ETH**, which acts as a security deposit. Once you're in, the Ethereum protocol randomly selects validators to **propose blocks** and **attest (vote) on blocks** proposed by others. Selection is influenced by factors like the amount of ETH staked and how long it’s been staked. + +Validators earn **rewards** for participating correctly—proposing valid blocks, attesting to others, and staying online. If they try to manipulate the system, go offline frequently, or break the rules, they can be **slashed** (a portion of their ETH is destroyed), which discourages bad behavior. + +This system is much more **energy-efficient** (reducing energy use by ~99.95%) and makes the network more **decentralized and scalable**. It also enables future improvements like **sharding**, where the network can process multiple groups of transactions in parallel to increase speed and capacity. + +Overall, PoS is a cleaner, smarter, and more secure way to run Ethereum, replacing brute-force mining with financial commitment and honest participation. + + +# Casper LMD-GHOST +Casper FFG (Friendly Finality Gadget) and LMD-GHOST (Latest Message Driven – Greediest Heaviest Observed SubTree) are both parts of Ethereum’s Proof of Stake consensus mechanism. + +#### CASPER FFG + +Casper is Ethereum’s Proof of Stake (PoS) consensus protocol, designed to replace the old Proof of Work (PoW) system. It’s made up of two key parts: Casper FFG (Friendly Finality Gadget) and LMD-GHOST (Latest Message Driven – Greediest Heaviest Observed SubTree). These two components work together to maintain network security, determine the canonical chain, and finalize blocks so they cannot be reversed. + +Casper FFG handles finality—the process of making blocks permanent. In Ethereum, time is split into slots (every 12 seconds) and epochs (32 slots). Validators are randomly selected to vote (or attest) on blocks during each slot. If two-thirds of validators agree on a checkpoint (a block marking the start of an epoch), it becomes justified. When two consecutive checkpoints are justified, the earlier one becomes finalized. Finalized blocks are considered irreversible unless a large portion of validators (at least one-third) behave maliciously and get penalized. + +Casper also includes slashing mechanisms to enforce honest behavior. Validators that break key rules—like signing conflicting votes or trying to finalize two different chains—can lose part or all of their staked ETH. This strong economic incentive discourages attacks and strengthens network security. + +Overall, Casper makes Ethereum more energy-efficient, secure, and scalable. It replaces wasteful mining with staking and coordinated validator voting, reducing energy use by over 99% and enabling future upgrades like sharding. It’s a major step in Ethereum’s evolution toward a more sustainable and performant blockchain. + +![Screenshot from 2025-04-08 11-26-34](https://hackmd.io/_uploads/SkZN5_M0ye.png) + + +This diagram illustrates the architecture of a sharded blockchain system, commonly associated with Ethereum 2.0. Here’s a breakdown of its components: + +**Components** + +1. **Main Chain**: + - **Purpose**: Handles staking, which is the process of locking up cryptocurrency to support the network in exchange for rewards. + +2. **Beacon Chain**: + - **Purpose**: Provides random numbers for validator selection and coordination between the shard chains and the main chain, enhancing security and performance. + +3. **Shard Chains**: + - **Purpose**: These chains (e.g., Shard 1, Shard 100) are responsible for processing transactions and storing data. Sharding divides the blockchain into smaller, manageable pieces, allowing parallel transaction processing to increase throughput. + +4. **VM (Virtual Machine)**: + - **Purpose**: Executes the smart contracts and transactions. It provides the state execution results based on the data and operations within the shard chains. + +**Flow Explanation** + +- The **Main Chain** connects to both the **Beacon Chain** and the **Shard Chains**. +- The **Beacon Chain** facilitates communication and coordination among the shards and ensures randomization for selecting validators. +- The **Shard Chains** contain blocks (like B1, B2, etc.), where data is stored and transactions are processed independently. +- Each block in the shard has a corresponding **state root**, which represents the current state of the data in that specific block. + +**Overall Process** + +- Transactions are processed in parallel across different shard chains, improving scalability. +- The Beacon Chain ensures the integrity and synchronization of these activities, while the Main Chain oversees the staking process. +- The document provides a visual representation of how the various layers of the blockchain architecture interact and function collectively to facilitate efficient transaction processing in a decentralized network. + +This layered approach significantly improves scalability, security, and efficiency compared to traditional single-chain blockchains. If you have more specific questions about any part of the diagram, feel free to ask! + + +#### LMD-GHOST +LMD-GHOST (Latest Message Driven – Greediest Heaviest Observed SubTree) is the fork-choice rule used in Ethereum’s Proof of Stake (PoS) protocol. Its primary purpose is to determine which block should be considered the head (or tip) of the blockchain—the block that new transactions and blocks should build upon. This process is crucial because, in a decentralized network, multiple blocks can be proposed at similar times, and the protocol needs a consistent and fair method for all nodes to agree on a single canonical chain. + +LMD-GHOST operates by starting from the most recent finalized block—a block that has received enough validator support to be considered irreversible—and works its way forward through the block tree. At every step, it evaluates the child blocks of the current block and chooses the one with the greatest total stake supporting it, based on validator attestations (votes). Importantly, LMD-GHOST uses a Latest Message Driven model, which means it only considers each validator’s most recent vote. This ensures the fork choice is always based on up-to-date information, making the system both efficient and responsive to changing network conditions. + +The “GHOST” part—Greediest Heaviest Observed SubTree—refers to how it picks the path forward. At each branching point, it selects the subtree with the most weight (i.e., the most ETH staked behind it via recent attestations) and continues down that path until it reaches the end. This greedy approach ensures the protocol favors the most-supported and honest version of the chain. + +By relying on recent, stake-weighted votes and prioritizing the heaviest-supported path, LMD-GHOST minimizes the risk of forks and keeps the chain aligned with the consensus of honest validators. It works hand-in-hand with Casper FFG, which handles block finalization, to provide Ethereum with a secure, scalable, and consistent PoS consensus mechanism. + +### GASPER + +**Gasper** is Ethereum’s hybrid Proof of Stake consensus protocol that combines **LMD-GHOST** (a fork-choice rule) and **Casper FFG** (a finality mechanism). LMD-GHOST ensures the chain grows along the path with the most recent and heavily-staked validator votes, while Casper FFG finalizes blocks by requiring a two-thirds supermajority of validator attestations across checkpoints. Together, they ensure the blockchain progresses securely and efficiently—LMD-GHOST handles selecting the latest valid block, and Casper FFG locks in blocks to prevent reversion—providing a balance of liveness and finality in Ethereum’s PoS system. + +# Checkpoint sync + +**Checkpoint sync** is a faster way for Ethereum nodes to join the network without downloading the entire blockchain history from the genesis block. Instead of starting from scratch, a node can begin from a recent **finalized checkpoint**, which is a block that has been confirmed by at least two-thirds of validators and is considered irreversible. + +Here’s how it works: +- The node downloads the **header** and **state** of a recent finalized checkpoint (usually from trusted peers or a checkpoint provider). +- It verifies this checkpoint using Ethereum’s consensus rules, including validator signatures. +- Once verified, the node syncs **forward** from that checkpoint to catch up with the current chain head, downloading only the most recent blocks and states. + +This method significantly reduces sync time and storage requirements, making it much easier and quicker for new nodes (especially light clients or validators) to get up to speed and participate in the network. + +# Consensus specification +Ethereum's **Consensus Specifications** define how the network reaches agreement on the state of the blockchain using **Proof of Stake (PoS)**. These specs describe the rules and logic that validators follow to propose, attest, and finalize blocks, ensuring Ethereum stays secure, decentralized, and up-to-date. The specifications are mainly split into the following core components: + + +1. **Beacon Chain** +- The backbone of Ethereum’s PoS system. +- Manages validator registration, rewards, penalties, and finality. +- Coordinates the consensus process across all shards and the main chain. + + + +**Validator Roles** +Validators perform the following duties: +- **Block Proposals**: Propose new blocks at assigned time slots. +- **Attestations**: Vote on the validity and head of the chain. +- **Sync Committees**: Provide light clients with recent chain data. +- **Aggregation**: Combine multiple attestations into single efficient messages. + + + +**Slots and Epochs** +- **Slot**: A 12-second time unit where a validator may propose a block. +- **Epoch**: A group of 32 slots (~6.4 minutes). +- Validators are assigned duties per slot and per epoch. + + + +**Finality Gadget – Casper FFG** +- Checkpoints are created every epoch. +- If 2/3 of validators vote to justify and then finalize two consecutive checkpoints, the earlier one becomes final. +- Finalized blocks cannot be reverted without severe validator penalties. + + + +**Fork-Choice Rule – LMD-GHOST** +- Determines the chain head by following the path with the highest total weight of recent validator attestations. +- Ensures honest validators agree on the same block as the chain tip. + + + +**Incentives and Slashing** +- Validators earn rewards for correct participation (proposals, attestations, sync duties). +- Misbehavior (e.g., double voting, surrounding votes) leads to **slashing**—loss of staked ETH and potential ejection from the network. + + + +**Checkpoint Sync** +- New or rejoining nodes can sync from a recent finalized checkpoint rather than downloading the entire chain. +- This improves sync speed and efficiency, especially for light clients. + + + +### Summary + +Ethereum’s consensus specifications define how validators maintain agreement on the network’s state using Casper FFG and LMD-GHOST under a PoS system. These rules manage everything from block proposal timing to finality and penalties, ensuring the network is secure, fair, and scalable.