diff --git a/docs/Serenity.md b/docs/Serenity.md new file mode 100644 index 000000000..9a190449f --- /dev/null +++ b/docs/Serenity.md @@ -0,0 +1,161 @@ +# Ethereum Serenity + +This document aims at providing a high level understanding of Ethereum and the +Serenity phase of the Ethereum roadmap. + +## The Blockchain + +A blockchain can be seen as a decentralized, distributed ledger. The ledger of +transactions is replicated onto all nodes in the network. When a transaction +occurs, it is first propagated to the nodes. Once the nodes receive the +transaction, and verifies the correctness, the nodes attempt to batch the +transactions into a block and append the block to the ledger. Once the ledger +has been successfully appended onto, they propagate the block to the network. +If accepted, this block now becomes the latest block in the chain. If two people +propose a block at the same time, the one canonical blockchain forks. At this +point it must be resolved, and each system has it's own way of resolving these +forks. + +![Blockchain](http://yuml.me/b0d6b30a.jpg) +
Figure 1. Example blockchain with a resolved fork.
+ +
+ +The idea of the blockchain was first proposed in the seminal [Bitcoin +whitepaper](https://bitcoin.org/bitcoin.pdf) by Satoshi Nakamoto. Since then, a +vast number of updates and blockchains have taken shape providing different +functionality or properties to the original blockchain. + +## What is Ethereum? + +Ethereum is an open blockchain protocol, allowing for the building and use of +decentralized applications that run on blockchain technology. Ethereum was one +of the initial platforms providing turing-complete code to be run on the +blockchain, allowing for conditional payments to occur through the use of this +code. Since then, Ethereum has advanced to allow for a number of Decentralized +Applications (DApps) to be developed and run completely with the blockchain as +the backbone. + +General Ethereum Introduction: + +* [What is Ethereum](http://ethdocs.org/en/latest/introduction/what-is-ethereum.html) +* [Ethereum Introduction](https://github.com/ethereum/wiki/wiki/Ethereum-introduction) + + +### Proof-of-Work and the current state of Ethereum. + +Currently, Ethereum is based on the Proof-of-Work model, a Sybil resilient +mechanism to allow nodes to propose blocks to the network. Although it provides +properties that allow the blockchain to operate in an open, public +(permissionless) network, it faces it's challenges and as a result impacts +the operation of the blockchain. + +The main goals to advance Ethereum is to (1) increase the scalability and +overall transaction processing power of the Ethereum world computer and (2) +find a suitable replacement for Proof-of-Work that still provides the necessary +properties that we need. + +* [Proof-of-Work in Cryptocurrencies: an accessible introduction](https://blog.sigmaprime.io/what-is-proof-of-work.html) + +## Serenity + +Ethereum Serenity refers to a new blockchain system currently under development +by the Ethereum Foundation and the Ethereum community. + +As part of the original Ethereum roadmap +[\[1\]](https://blog.ethereum.org/2015/03/03/ethereum-launch-process/) +[\[2\]](http://ethdocs.org/en/latest/introduction/the-homestead-release.html), +the Proof-of-Stake integration falls under **Release Step 4: *Serenity***. With +this, a number of changes are to be made to the current Ethereum protocol to +incorporate some of the new Proof-of-Stake mechanisms as well as improve on +some of the hindrances faced by the current Proof-of-Work chain. + +To now advance the current Ethereum, the decision is made to move to a sharded +Beacon chain structure where multiple shard-chains will be operating and +interacting with a central beacon chain.The Serenity blockchain consists of +1,025 proof-of-stake blockchains. This includes the "beacon chain" and 1,024 +"shard chains". + +Ethereum Serenity is also known as "Ethereum 2.0" and "Shasper". We prefer +Serenity as it more accurately reflects the established Ethereum roadmap (plus +we think it's a nice name). + +(Be mindful, the specifications change occasionally, so check these to keep up +to date) + +* Current Specifications: + * [Danny Ryan's "State of the Spec"](https://notes.ethereum.org/s/BJEZWNoyE) (A nice summary of the current specifications) + * [Ethereum Serenity - Phase 0: Beacon Chain Spec](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md) + * [Ethereum Serenity - Phase 1: Sharded Data Chains](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/1_shard-data-chains.md) + * [Beacon Chain - Vitalik Buterin and Justin Drake explain](https://www.youtube.com/watch?v=GAywmwGToUI) +* Understanding Sharding: + * [Prysmatic Labs: Sharding Explained](https://medium.com/prysmatic-labs/how-to-scale-ethereum-sharding-explained-ba2e283b7fce) +* Other relevant resources + * [Proof of Stake - Casper FFG](https://www.youtube.com/watch?v=uQ3IqLDf-oo) + * [Justin Drake VDF Devcon4 Talk](https://www.youtube.com/watch?v=zqL_cMlPjOI) + + +### Beacon Chain + +The concept of a beacon chain differs from existing blockchains, such as +Bitcoin and Ethereum, in that it doesn't process transactions per se. Instead, +it maintains a set of bonded (staked) validators and coordinates these to +provide services to a static set of *sub-blockchains* (i.e. shards). Each of +these shard blockchains processes normal transactions (e.g. "Transfer 5 ETH +from A to B") in parallel whilst deferring consensus mechanisms to the beacon +chain. + +Major services provided by the beacon chain to its shards include the following: + +- A source of entropy, likely using a [RANDAO + VDF + scheme](https://ethresear.ch/t/minimal-vdf-randomness-beacon/3566). +- Validator management, including: + - Inducting and ejecting validators. + - Assigning randomly-shuffled subsets of validators to particular shards. + - Penalizing and rewarding validators. +- Proof-of-stake consensus for shard chain blocks. + +### Shard Chains + +Shards are analogous to CPU cores - they're a resource where transactions can +execute in series (one-after-another). Presently, Ethereum is single-core and +can only _fully_ process one transaction at a time. Sharding allows processing +of multiple transactions simultaneously, greatly increasing the per-second +transaction capacity of Ethereum. + +Each shard uses a proof-of-stake consensus mechanism and shares its validators +(stakers) with other shards. The beacon chain rotates validators +pseudo-randomly between different shards. Shards will likely be the basis of +layer-2 transaction processing schemes, however, that is not in scope of this +discussion. + +### The Proof-of-Work Chain + +The present-Ethereum proof-of-work (PoW) chain will host a smart contract that +enables accounts to deposit 32 ETH, a BLS public key, and some [other +parameters](https://github.com/ethereum/eth2.0-specs/blob/master/specs/casper_sharding_v2.1.md#pow-chain-changes), +allowing them to become beacon chain validators. Each beacon chain will +reference a PoW block hash allowing PoW clients to use the beacon chain as a +source of [Casper FFG finality](https://arxiv.org/abs/1710.09437), if desired. + +It is a requirement that ETH can move freely between shard chains, as well as between +Serenity and present-Ethereum blockchains. The exact mechanics of these transfers remain +an active topic of research and their details are yet to be confirmed. + +## Serenity Progress + +Ethereum Serenity is not fully specified and a working implementation does not +yet exist. Some teams have demos available which indicate progress, but do not +constitute a complete product. We look forward to providing user functionality +once we are ready to provide a minimum-viable user experience. + +The work-in-progress specifications live in the +[ethereum/eth2.0-specs](https://github.com/ethereum/eth2.0-specs) repository. +There is active discussion about the specification in the +[ethereum/sharding](https://gitter.im/ethereum/sharding) gitter channel. A +proof-of-concept implementation in Python is available at +[ethereum/beacon_chain](https://github.com/ethereum/beacon_chain). + +Presently, the specification focuses almost exclusively on the beacon chain, +as it is the focus of current development efforts. Progress on shard chain +specification will soon follow.