Thread by @expctchaos

0/ Polygon #Avail is a chain-agnostic, modular data availability blockchain built by @0xPolygon. Like @CelestiaOrg, it aims to provide rollups & L1s with a highly scalable DA & consensus layer ✨

A 🧵 on how #Polygon's specialized DA layer works & compares to Celestia (0/34) 👇

@0xPolygon @CelestiaOrg 1/ @0xPolygon has been stealth building Avail since 2020 & has announced the testnet for Q2 2022 in April:

https://twitter.com/0xPolygon/status/1511709595060031491

@0xPolygon @CelestiaOrg 2/ Unlike @CelestiaOrg, Polygon #Avail is not built on the #Cosmos SDK and not using Tendermint BFT. However, Avail is also a PoS network, using a nominated Proof of Stake consensus algorithm

@0xPolygon @CelestiaOrg 3/ But let's have a look at how Avail works in more detail and investigate how it compares to #Celestia architecturally

@0xPolygon @CelestiaOrg 4/ The problem #Avail tries to solve is the same as Celestia. Monolithic L1 chains face the state bloat issue, State bloat occurs as more transactions are added to a blockchain’s ledger

@0xPolygon @CelestiaOrg 5/ Consequently, the state of the blockchain (information necessary to execute txs) grows and in turn makes it more costly to run a full node (because of increased hardware requirements)

@0xPolygon @CelestiaOrg 6/ This results in an undesired scenario in which the number of full nodes starts to decrease and light nodes start to increase, centralizing the network around consensus nodes and making it more vulnerable to malicious full node behavior

@0xPolygon @CelestiaOrg 7/ This is exactly why most chains limit the rate at which their state grows by enforcing a block/gas size limit. As many blockchains value decentralization among the validator set, they have an interest in enabling their community to run full nodes on consumer hardware

@0xPolygon @CelestiaOrg 8/ Like #Celestia, #Avail takes modular approach. The modular architecture includes:

- Data Availability Layer (Avail)

- Settlement Layer ($ETH)

- Execution Layer (Rollup)

@0xPolygon @CelestiaOrg 9/ Data Availability Layer:

Storing data and providing consensus, while ensuring data availability for the execution layers built on top of #Avail

@0xPolygon @CelestiaOrg 10/ Settlement Layer:

Layer on which verifier contracts are run and state changes from execution layers are "settled"

@0xPolygon @CelestiaOrg 11/ Execution Layer:

The execution layer is where the actual computation happens. Applications are built and users interact with them on rollups. Rollups store data on #Celestia and post attestations on the settlement layer

@0xPolygon @CelestiaOrg 12/ But before diving into #Avail, let's quickly recall the type of nodes that (high-level) exist in blockchain networks:

@0xPolygon @CelestiaOrg 13/ Full Nodes:

https://twitter.com/expctchaos/status/1535970231331328000

@0xPolygon @CelestiaOrg 14/ Light Clients:

https://twitter.com/expctchaos/status/1535970233864683522

@0xPolygon @CelestiaOrg 15/ Bc light clients do not download the entire block, they can be tricked into accepting blocks whose underlying data is not available. The block producer might include a malicious tx in a block & not reveal its entire content to the network

@0xPolygon @CelestiaOrg 16/ This is known as the data availability problem & poses serious threats to light clients in traditional blockchain architecture

@0xPolygon @CelestiaOrg 17/ Like #Celestia, Avail addresses this problem .  Instead of verifying the application state, it focuses only on ensuring the availability of the tx data posted & ensures tx ordering. A block that has consensus is considered valid only if the data behind the block is available

@0xPolygon @CelestiaOrg 18/ Like in @CelestiaOrg DA is ensured by a scalable network of data sampling light clients

For more info on data availability sampling see here 👇

https://twitter.com/expctchaos/status/1535970261769457664

@0xPolygon @CelestiaOrg 19/ This let's light clients operate under almost same security assumptions as full nodes (as long as there is at least one honest full node)

@0xPolygon @CelestiaOrg 20/ But while @CelestiaOrg relies on a fraud proof system to enable these security guarantees for light nodes, @0xPolygon #Avail uses a KZG commitment scheme

@0xPolygon @CelestiaOrg 21/ #Avail's KZG commitment scheme has three main features:

- Data redundancy (erasure coding)

- Fraud proof free guarantee of correct erasure coding

- Kate commitments allow full nodes to prove tx inclusion to light nodes using succinct proof

@0xPolygon @CelestiaOrg 22/ In simple terms, the entire data in a block is arranged as a two-dimensional matrix. The data redundancy is brought in by erasure coding each column of the matrix to double the size of the original one

@0xPolygon @CelestiaOrg 23/ Kate commitments are used to commit to each of the rows & the commitment is included in the block header. The scheme makes it easy to catch a data hiding attempt as any light client...

@0xPolygon @CelestiaOrg 24/ ...with access to only block headers can query random cells of the matrix and get short proofs (thanks to the Kate commitments) that can be checked against the block headers

@0xPolygon @CelestiaOrg 25/ If you need a recap on erasure coding see 👇

https://twitter.com/expctchaos/status/1535970246653190145

@0xPolygon @CelestiaOrg 26/ Like with #Celestia, a very powerful feature that the light node network enables, is that the Avail network scales (increasing block size) with a growing number of data sampling light nodes

@0xPolygon @CelestiaOrg 27/ So how can rollups use the Avail layer? Simple, instead of posting full data to $ETH base layer rollups can choose to become a Avail-based #Validium, storing only proofs that the data is available on $ETH L1, instead of posting the full tx data (like Celestiums)

@0xPolygon @CelestiaOrg 28/ Most current #Validiums on $ETH use permissioned data availability committees (DACs), which are small groups of institutions that post signatures back to $ETH L1, attesting to the availability of the data off-chain. They are responsible for ensuring data is always accessible

@0xPolygon @CelestiaOrg 29/ #Avail provides a decentralized alternative to DACs. While DACs only have 5-20 members, Avail plans to have a permissionless network of hundreds of nodes, significantly strengthening network security & adding a security layer in the form of economic incentives (e.g. slashing)

@0xPolygon @CelestiaOrg 30/ Thanks to its chain-agnostic nature and scalable, modular architecture, @0xPolygon will be able to support an almost infinite amount of rollups, just like @CelestiaOrg

@0xPolygon @CelestiaOrg 31/ The benefits of #Polygon #Avail compared to monolithic L1 infrastructure are:

- Self-Sovereign rollups
- Flexibility (arbitrary VM support)
- Efficient pricing (historical data vs execution)
- High security guarantees for light clients
- Network scales with # light clients

@0xPolygon @CelestiaOrg 32/ These benefits are very much in line with the advantages Celetia offers as well. If you need more detail or want to catch up on Celestia's approach, read this thread 👇

https://twitter.com/expctchaos/status/1535970188012572672

@0xPolygon @CelestiaOrg 33/ But with both networks having such a similar architecture, who will emerge as the winner?

Well, I think Celestia will likely beat Avail to market & have likely have first mover advantage. However, I see 0xPolygon in a strong position to even this out (standing in $ETH eco)

@0xPolygon @CelestiaOrg 34/ In the long-term I think both will prosper as we finally enter the era of true, multi-layered scaling:

https://twitter.com/epolynya/status/1463867717702742022