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6 types of blockchain consensus mechanisms

6 types of blockchain consensus mechanisms


Blockchains are distributed systems in which records of digital transactions are both publicly verifiable and immutable. Each new transaction is included in a block along with other recent transactions, and the block is then added to a chain of other blocks (hence the term ‘blockchain’).

For a blockchain to operate successfully, the participants – also known as nodes – need to agree on the validity of each new block. Blockchains can use different variations of different consensus protocols to determine eligibility of block-producing nodes.

To ensure continuity, block producers must reach consensus on a particular transaction history. This is achieved by a specific consensus mechanism that guarantees that the participant’s views converge to the same history of events. This ensures trust in the blockchain as a whole, without the need to trust specific participants. Mutually distrustful entities can still participate in the blockchain, comfortable in the knowledge that the blockchain itself can arbitrate and verify their actions.

Different protocols provide varying levels of security, scalability, and decentralization. Each consensus mechanism might claim to be the 'best' solution.

Let’s take a look at six blockchain protocols.

What are the most prevalent consensus mechanisms?

Two of the best-known consensus protocols are proof of work (PoW) and proof of stake (PoS), but others (and multiple variations on the above) also exist. Let’s delve into how some of these mechanisms work and what sets them apart.

Proof of work (PoW)

PoW was the first blockchain consensus mechanism with Satoshi Nakamoto applying this model to the Bitcoin chain in 2009.

PoW relies on competition between computers (miners) to solve moderately hard puzzles. The next miner to find a possible solution to a query gets to mine a new block on the blockchain.

Ergo and Ethereum Classic also use PoW.

Here are a few advantages and disadvantages to think about before committing to a PoW chain:


  • Attacking a PoW chain would require controlling 51% of the network's computing power – a process that is too expensive for hackers.


  • The high energy consumption used in solving queries (because miners are all actively competing to mine a block) is a major disadvantage of PoW chains.

  • Expensive and specialized hardware is required to become a miner, thus hindering decentralization.

  • PoW has scalability limitations due to the network's design, which limits block size and creation time.

Proof of stake (PoS)

PoS is a newer, less energy-intensive, and thus more sustainable consensus mechanism than PoW. Through PoS consensus, holders of a blockchain asset can participate in securing and validating on-chain transactions by delegating their stake to a validator.

Launched in 2012, Peercoin was the first PoS project. Cardano, Polygon, and Tezos are three popular PoS blockchains. Ethereum has recently moved from PoW to PoS after a successful ‘Merge’.

It is important to note that unlike Ethereum’s version of PoS, however, Cardano’s PoS mechanism:

  • Enables liquid staking (i.e. no lock-up) through which holders of Cardano native tokens can withdraw their stake or delegate it to another validator (stake pool) at any time.

  • Requires a small initial amount of 2.17 ada to start staking

  • Has no slashing feature that risks unfairly punishing delegators for staking to nodes that do not operate as intended.

Ouroboros is Cardano’s PoS consensus protocol and was the first provably secure PoS protocol. In other words, Ouroboros offers mathematically verifiable security against attackers. The protocol is guaranteed to be secure, as long as 51% of the stake is held by honest participants. According to Google scholar, the original paper has been academically cited more than 1400 times, and variants of the protocol are used on other PoS chains. 

Let’s look at the pros and cons of PoS:



  • Validators on some PoS consensus mechanisms must lock up a small amount of their assets (pledge), which can’t be unstaked for a set period.

    Note: This doesn’t apply to Cardano.

  • Validators with the largest amounts of staked assets or multiple pools have significant influence in validating transactions, which could pose security risks.

  • With some chains, delegators and validators can risk losing part of their staked funds (slashing) if validators validate inaccurate transactions, go offline along with other validators, or attack the network.

    Note: There is no such slashing on Cardano.

  • PoS systems with a small number of active validators or those that overly rely on centrally hosted Cloud services (vs bare metal, self-hosted nodes) reduce decentralization.

Delegated proof of stake (DPoS)

DPoS is a modified PoS consensus mechanism that implements a voting system with two actors: delegates and voters.

Voters stake their assets and elect delegates to validate transactions on the network. This means that a delegate’s ability to become and remain a validator depends on their reputation. One mistake and they can be removed and replaced. Maintaining their reputation, therefore, becomes crucial.

WAX and EOS are DPoS blockchains.

The advantages and disadvantages of a DPoS consensus mechanism include:


  • Transactions are fast on a DPoS network due to the limited number of validators, enabling faster consensus. 

  • A DPoS consensus protocol blockchain remains secure through voting. Any delegate that behaves suspiciously can be voted out instantly.

  • A DPoS blockchain is very energy efficient.


  • DPoS networks may be more susceptible to a 51% attack due to the relatively small number of validators. This attack occurs when over 50% of the chain’s stake is controlled by one individual or group.

  • DPoS blockchains are more centralized than chains with some of the other consensus mechanisms because of fewer validators on a DPoS chain.

  • Voters with more staked assets are more influential.

Proof of authority (PoA)

PoA is a consensus model that might better suit private networks. Instead of staking the chain’s digital assets, a committee is entrusted to perform validation – in contrast to public (i.e., permissionless) participation.

The PoA consensus mechanism determines a fixed set of nodes to perform chain maintenance. These nodes earn the exclusive right to secure the network and validate transactions.

VeChain and private networks such as JP Morgan’s Coin Systems use this mechanism.

A PoA protocol has the following pros and cons:


  • As with PoS, this model is energy-efficient and doesn’t require expensive hardware or high computational power.


  • The blockchain is maintained by a small number of approved validators, meaning it is not truly decentralized.

  • Becoming a validator requires a lot of fiat, making it harder for most people to participate in the process.

Proof of capacity (PoC)

PoC – also known as proof of space – requires miners to have available disk space to obtain mining rights and validate transactions. Similarly to PoW, in PoC, the rights to produce a new block are assigned proportionally to the space (instead of computational power) a given miner dedicates to the PoC system.

Blockchains using PoC include Chia, Signum (formerly known as Burstcoin), SpaceMint, and Storj.


  • Block mining does not require high energy consumption as block producer election depends on available disk space.

  • Any standard hard disk is compatible with PoC.

  • The drive can be used for any other data storage purpose after mining data has been removed, unlike in PoW mechanisms where hardware is only used to mine.

  • Nodes do not require hard drive upgrades or specialized hardware, they only require disk space.


  • If the PoC model gains greater popularity, the mechanism could increase demand for higher capacity storage to boost a miner’s chances of validating a block.

Proof of useful work (PoUW): a new and sustainable consensus mechanism

The blockchain industry is still relatively new, having existed for not much longer than a decade. Organizations and blockchain projects continuously look into how to build and improve on consensus mechanisms.

Input Output Global is one such example with its recent research into Ofelimos – a novel proof of useful work (PoUW) consensus mechanism that seeks to minimize the energy wastage in a PoW mechanism.

At the time of writing, no blockchain uses PoUW and any pros and cons of this consensus mechanism are only theoretical. Here's a possible advantage and a presumed disadvantage of Ofelimos:


  • PoUW ensures that at least some of PoW’s computational energy expenditure is used to solve complex real-world problems. Examples might include DNA sequencing, distributed computation, protein unfolding, urban planning, and more.


  • The PoUW model requires a continuous stream of complex real-world queries to solve, otherwise, there’s an unnecessary loss of computational power like in PoW protocols.

Learn more about this new model by reading this in-depth article.










プルーフオブワーク(Proof of work:PoW)



ErgoEthereum ClassicもPoWを使用しています。



  • PoWチェーンを攻撃するためには、ネットワークの計算力の51%をコントロールすることが必要となる、すなわち、ハッカーにとってプロセスが高額になりすぎる


  • クエリの解決にエネルギーを大量に消費する(_すべて_のマイナーがブロックのマイニングのために積極的に競争するため)ことは、PoWチェーンの大きな欠点

  • マイナーになるためには、高額な専用ハードウェアが必要であるため、分散化の妨げとなる

  • PoWはネットワークの設計上スケーラビリティに限界があるため、ブロックサイズと生成時間が限定される

プルーフオブステーク(Proof of stake:PoS)


2012年に立ち上げられたPeercoinは、最初のPoSプロジェクトです。CardanoPolygonTezosは、三大PoS ブロックチェーンです。イーサリアムは最近無事に「マージ」して、PoWからPoSに移りました。


  • Cardanoネイティブトークン保有者がいつでもステークを引き出したり他のバリデーター(ステークプール)に委任することができる流動ステーキング(ロック無し)が可能

  • ステーキングを始めるには最初に2.17ADAという少額の資金が必要

  • 意図したとおりに運営しないノードにステーキングしたデリゲーター(委任者)を不当に罰する怖れのあるスラッシング機能はない

Ouroboros(ウロボロス)はCardanoのPoSコンセンサスプロトコルであり、最初の証明可能安全性を持つPoSプロトコルです。言い換えれば、Ouroborosは攻撃に対し_数学的に検証可能な_安全性を持ちます。このプロトコルは、ステークの51%が誠実な参加者に保有されている限り、安全であることが保障されます。Google scholarによれば、オリジナルの論文は1400回以上学術的に引用されており、このプロトコルのバリエーションが他のPoSチェーンで使用されています。 




  • PoSコンセンサスプロトコルによっては、バリデーターが少額の資産をロックする必要があり(プレッジ)、この資産は一定期間ステークできない


  • ステーク資産の最大額を持つ、あるいは複数のプールを持つバリデーターがトランザクションの検証に大きな影響を及ぼすことで、セキュリティリスクにつながる恐れがある

  • チェーンによっては、バリデーターが不正確なトランザクションを有効とする、または、他のバリゲーターと一緒にオフラインになる、ネットワークを攻撃するなどした場合に、デリゲーターとバリデーターがステークした資金の一部を失う(スラッシング)リスクがある


  • アクティブなバリデーターが少数のPoSシステムや、一元的にホストされているクラウドサービス(対してベアメタル、セルフホストノード)に過剰に依存しているPoSシステムは分散化が低下する

委任型プルーフオブステーク(Delegated proof of stake:DPoS)






  • DPoSネットワークではバリデーターの数が限られていることからコンセンサスが迅速であり、トランザクションの高速化が可能 

  • DPoSコンセンサスプロトコルブロックチェーンでは投票を介して安全性が保たれる。疑わしい行動をするデリゲートは即座に投票で落とされる

  • DPoSブロックチェーンは非常にエネルギー効率が良い


  • DPoSネットワークはバリデーターの数が比較的少数であることから、51%攻撃に対してより脆弱となる可能性がある。この攻撃は、チェーンで50%を超えるステークが1個人や1グループにコントロールされると発生する

  • DPoSブロックチェーンは、バリデーターの数が他に比べて少ないため、他の一部のコンセンサスメカニズムのチェーンよりも中央集権化しやすい

  • 多くのステーク資産を持つ投票者ほど、影響力が増す

プルーフオブオーソリティ(Proof of authority:PoA)



VeChainや、JP MorganのCoin Systemsといったプライベートネットワークはこのメカニズムを採用しています。




  • ブロックチェーンは承認された少数のバリデーターによって保守されるため、真の意味で分散型とは言えない

  • バリデーターになるには多額のフィアットが必要であるため、ほとんどの人にとってプロセスに参加することは困難

プルーフオブキャパシティ(Proof of capacity:PoC)




  • ブロック生成者はディスク容量に基づいて選定されるため、高い電力消費は必要にならない

  • PoCは標準ハードディスク対応

  • ハードウェアをマイニング専用にしか使えないPoWシステムとは異なり、ドライブはマイニングデータの削除後に別のデータストレージとして利用可能

  • ノードによりハードドライブのアップグレードや専用ハードウェアが必要となることはなく、必要なのはディスク容量のみ


  • PoCモデルの人気が高まると、マイナーがブロックを検証するチャンスを高めるために、より大容量のストレージの需要が高まる可能性がある

プルーフオブユースフルワーク(Proof of useful work:PoUW):サステナブルな新型コンセンサスメカニズム


Input Output Global最近の研究Ofelimosはその好例です。これは、プルーフオブ_ユースフル_ワーク(PoUW)という新しいコンセンサスメカニズムで、PoWメカニズムのエネルギー浪費を最小に抑えることを目指しています。



  • PoUWは、PoWの計算にかかるエネルギー消費の少なくとも一部を、複雑な実世界の問題を解決するために使用する。この例としては、DNA塩基配列決定、分散コンピューティング、タンパク質のアンフォールディング、都市計画など


  • PoUWモデルでは、解決を要する複雑な現実世界のクエリの継続的なストリームが必要。そうでなければ、PoW同様に計算能力を無駄に損失することになる