Classification of Blockchains

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This post is part of our Blockchains Study Group. Take a look there to learn more about related topics.

In the Telegram white paper, they present a very useful classification of blockchains. I think it is a little biased to present their own blockchain as the final step in the evolution of this technology, but it's very useful nevertheless. We will use it as a base to classify the projects we are learning about in our blockchains study group.

As usual, this post is a wiki that will grow over time. Feel free to leave a comment or edit it directly.

This is the criteria we will use to classify blockchains:

  • Chain architecture: single-blockchain or multi-blockchain.
    For multi-blockchain systems:
    • Types and rules of member blockchains: homogeneous, heterogeneous, mixed.
    • Presence of a master chain, internal or external.
    • Support for sharding, static or dynamic.
    • Interaction between member blockchains, loosely or tightly-coupled.
  • Consensus mechanism: Proof-of-Stake, Proof-of-Work, or Proof-of-Authority.
    For Proof-of-Stake systems:
    • Consensus algorithm: Byzantine Fault Tolerance, Delegated Proof of Stake, etc.
      In particular:
      • Who can produce or mine a new block?
      • Are the blocks validated by validator signatures, or are all full nodes expected to validate them?
      • Is there a designated producer for the next block? Is it known in advance?
      • Is a newly-created block originally signed only by its producer, or must it collect a majority of validator signatures from the very beginning?
  • Support for smart contracts: only value transfers, limited scripting, or Turing-complete.
  • Permissioned or permissionless.

Here are a few examples:

  • Bitcoin, Litecoin, Monero: single-blockchain, Proof-of-Work, no support for smart contracts.
  • Ethereum: single-blockchain, Proof-of-Work, with support for smart contracts.
  • Ethereum 2.0: multi-blockchain with masterchain and sharding, Proof-of-Stake, with support for smart contracts.
  • Polkdadot: multi-blockchain with masterchain, Proof-of-Stake, with support for smart contracts.
  • Telegram Open Network: multi-blockchain with master chain, Proof-of-Stake, with support for smart contracts.

In the following months we will be exploring some of these blockchains more in-depth.

Thanks to Nikolai Durov and the Telegram Open Network team for proposing this classification.

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Blockchains Study Group
Polkadot [in progress]
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Hi @elopio,

Is there room to include Proof-of-Authority?

Whilst PoA blockchains are not trustless (they are secured by the reputation of the authorities), they are an important part of the Ethereum eco-system. Including public testnets: Rinkeby, Kovan and Goerli, and sidechains such as xDAI.

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Yes, of course. I’m adding this mechanism, and we can explore them in the study group.

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Thank you for the summary. My own classification is PoW-style, PoS-style, and others… maybe BFT-style(I don’t know the details for each consensus mechanism :sweat_smile:).

I think there are many consensus models in “private” chain such as Clique(PoA in Geth), Aura(PoA in Parity?), IBFT, PBFT, Raft and so on. I hope someone makes them simple!

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@swkim109 We will try to explain all of these topics in a simple way :slight_smile: You are welcome to ask questions if it is not clear enough. Or, if you have the time, it will be awesome if you write a summary about one of those. Then we can all continue improving it.

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@elopio Have you considered permissioned vs permisionless blockchains as part of the classification?

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We haven’t. I have just added it, thanks Fran.

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