PoW idea was originally published by Cynthia Dwork and Moni Naor back in 1993, but the term “proof of work” was coined by Markus Jakobsson and Ari Juels in a document published in 1999. But, returning to date, Proof of work is maybe the biggest idea behind the Nakamoto’s Bitcoin white paper – published back in 2008 – because it allows trustless and distributed consensus.

In Blockchain, this algorithm is used to confirm transactions and produce new blocks to the chain.

With PoW, miners compete against each other to complete transactions on the network and get rewarded. In a network, users send each other digital tokens. A decentralized ledger gathers all the transactions into blocks.

However, care should be taken to confirm the transactions and arrange blocks. This responsibility bears on special nodes called miners, and a process is called mining. The main working principles are a complicated mathematical puzzle and a possibility to easily prove the solution.

PoW is particularly for cryptocurrencies, and the most utilized system of all. This is presumably the case because since 2009 it has officially demonstrated its strength and security.

Mining is the central part of the majority of the modern digital forms of money and prominent Blockchain applications. Additionally, for the Ethereum, a transaction must be bundled into blocks with a specific goal to be declared as a major aspect of the history. Thus, it has been named as Proof of Work.

Basically, it portrays the conditions that members of the system must demonstrate how many functions they have spent so as to have the capacity to confirm transactions. In this way, they get compensated for each block that they approve and confirm. The surplus on the compensating sums is a benefit for the miners and serves as an incentive. Altogether, the reward for a block comprises of the general block remuneration and the total of all expenses from all exchanges contained in the block.

Moreover, the high monetary contribution of miners guarantees that the produced coins are really upheld by genuine incentive in respect of fiat money. Thus, mining is the flow of fiat cash into coins of a digital currency.

The main goal of PoW is deterring cyber-attacks such as a distributed denial-of-service attack (DDoS) which has the purpose of exhausting the resources of a computer system by sending multiple fake requests.



Proof of stake first idea was suggested on the bitcointalk forum back in 2011, but the first digital currency to use this method was Peercoin in 2012, together with ShadowCash, Nxt, BlackCoin, NuShares/NuBits, Qora, and Nav Coin.

Unlike the proof-of-Work, where the algorithm rewards miners who solve mathematical problems with the goal of validating transactions and creating new blocks, with the proof of stake, the creator of a new block is chosen in a deterministic way, depending on its wealth, also defined as stake.

Also, all the digital currencies are previously created in the beginning, and their number never changes. This means that in the PoS system there is no block reward, so, the miners take the transaction fees. This is why, in fact, in this PoS system miners are called forgers, instead.

Like in a business entity, shareholders have a privilege of partaking in this consensus mechanism thus, it is known as Proof of Stake (PoS).

With Bitcoin’s high cost of mining, blockchain drivers looked for less expensive options that didn’t require consuming high measures of energy. The energy utilization is constrained to the use and approval actions of users and isn’t misleadingly expanded by superfluous complicated calculations. The first of these choices is PoS, which allows the level of duty in keeping up general community ledger to a node as indicated by the number of coins it handles. The more coins a node carries, the more possibilities it has of being chosen to refresh the ledger.

As POS needs neither particular hardware nor the burning of energy, it is one of the least expensive blockchain consensus conventions. It is additionally amongst the most comprehensive since all the coin holders in a system have an opportunity to take an interest in the mining procedure.

Proof-of-stake currencies can be more energy efficient than currencies based on proof-of-work algorithms.

Incentives also differ between the two systems of block generation. Under proof of work, miners may potentially own none of the currency they are mining and thus seek only to maximize their own profits. It is unclear whether this disparity lowers or raises security risks. Under proof of stake, however, those “guarding” the coins always own the coins, although several cryptocurrencies do allow or enforce the lending of staking power to other nodes.



Now we approach an intriguing type of Proof of Stake called Delegated Proof of Stake (or DPOS) presented by University of Michigan researchers Eric Wustrow and Benjamin Vander Sloot. EOS is utilizing this mechanism to scale up to a large number of exchanges every second. Other blockchains that use this mechanism are Lisk, Steem, BitShares, and Ark.

DPoS seeks to speed up transactions and block creation, while not compromising the decentralized incentive structure at the heart of the blockchain. Initially, any individual who holds tokens on a Blockchain coordinated in the EOS programming can choose the block makers through a constant approval voting network. Anybody can partake in the block generator election and they will be provided a chance to create blocks proportionate to the aggregate votes they get with respect to every single other generator. In the event that they can really pull it off, at that point they will have the DPoS to thank.

They are much faster than tradition Proof of Work and Proof of Stake systems. Their incentives and structures enhance the security and integrity of their blockchains, and each user has an incentive to perform their role honestly. No specialized equipment is required to become a user, witness, or delegate. A normal computer is enough. They are energy efficient compared to power-hungry Proof of Work hashing algorithms.

DPoS is the next step in the evolution of consensus mechanisms. It builds on the original Proof of Stake consensus mechanism and drastically increases speed and scalability.



Proof of burn is a method for distributed consensus and an alternative to Proof of Work and Proof of Stake. It can also be used for bootstrapping one cryptocurrency off of another.

The idea is that miners should show proof that they burned some coins – that is, sent them to a verifiably unspendable address. This is expensive from their individual point of view, just like proof of work; but it consumes no resources other than the burned underlying asset. To date, all proof of burn cryptocurrencies work by burning proof-of-work-mined cryptocurrencies, so the ultimate source of scarcity remains the proof-of-work-mined “fuel”.

Value of one digital currency can be exchanged then onto the next through the Proof of Burn (PoB) mechanism. This implies a node takes part in a lottery to choose the status of the blockchain by burning value they as of now hold, as another cryptographic money, for example, bitcoin or ether.

To locate the following block, the node transfers bitcoin, ether or some other digital currency to an unspent address. In return, the node gets a reward in the coins local to the Blockchain it supports to sustain.

The principal Blockchain to effectively apply the PoB mechanism for mining was Slimcoin an alternative cryptocurrency based on Peercoin, uses Proof of burn as part of its consensus algorithm and alternative mining/minting method.

Participants with full Slimcoin nodes can earn coins finding Proof of Burn blocks. The probability of a participant (identified by its address or public key) to find a block is being determined by a score called Effective Burnt Coins based on the number of coins burnt from its address. Burnt coins decay over time: the Effective Burnt Coins score is reduced every Proof-of-work block, dropping to zero after several years.

Its system consolidates Proof of Burn with PoW and PoS, making it the first cryptocurrency to join three consensus mechanisms.



Practical Byzantine Fault Tolerance (pBFT) is one of these optimizations and was introduced by Miguel Castro and Barbara Liskov in an academic paper in 1999 titled “Practical Byzantine Fault Tolerance”. It aims to improve upon original BFT consensus mechanisms and has been implemented and enhanced in several modern distributed computer systems, including some popular blockchain platforms.

The PBFT model primarily focuses on providing a practical Byzantine state machine replication that tolerates Byzantine faults (malicious nodes) through an assumption that there are independent node failures and manipulated messages propagated by specific, independent nodes. The algorithm is designed to work in asynchronous systems and is optimized to be high-performance with an impressive overhead runtime and only a slight increase in latency.

Distributed networks could use Practical Byzantine fault-tolerant (PBFT) mechanism. Every node distributes a public key. Messages getting through the node is designated by the node to confirm its organization. When enough indistinguishable reactions are achieved, at that point a consensus is met that the message is a legitimate transaction.

PBFT is a network formed for the low-latency storage framework. This is pertinent to digital resource-based platforms that don’t need a lot of throughputs yet ask numerous transactions. Besides, trust is completely decoupled from asset possession, which makes it feasible for a non-profit to keep capable small organizations legit.

One of the primary advantages of the pBFT model is its ability to provide transaction finality without the need for confirmations like in Proof-of-Work models such as the one Bitcoin employs. If a proposed block is agreed upon by the nodes in a pBFT system, then that block is final. This is enabled by the fact that all honest nodes are agreeing on the state of the system at that specific time as a result of their communication with each other. Another important advantage of the pBFT model compared to PoW systems is its significant reduction in energy usage. With pBFT not being computationally intensive, a substantial reduction in electrical energy is inevitable as miners are not solving a PoW computationally intensive hashing algorithm every block.

Limitations – The model only works well in its classical form with small consensus group sizes due to the cumbersome amount of communication that is required between the nodes. The pBFT model is also susceptible to Sybil attacks where a single party can create or manipulate a large number of identities (nodes in the network), thus compromising the network. This is mitigated against with larger network sizes, but scalability and the high-throughput ability of the pBFT model is reduced with larger sizes and thus needs to be optimized or used in combination with another consensus mechanism.

Not at all like PoW and PoS, a PBFT consensus mechanism does not require any hashing energy to approve exchanges in a blockchain, which implies there is no requirement for high energy utilization and the danger of centralization is lower than in both of those blockchain mechanisms.PBFT is presently being utilized by the Hyperledger venture, which enables developers to fabricate their own particular digital resources on a disseminated ledger.


Proof of Identity (PoI) is cryptographic evidence (piece of data) which tells that any user knows a private key that compares to an authorized identity and cryptographically attached to a specific transaction. Every individual from some group can create a PoF (only a block of data) and present it to anyone for instance to the processing node.

Proof of Identity, establishes the person as one and only one person, therefore entitled to one and only one vote.



Proof of elapsed time (PoET) is a blockchain network consensus mechanism algorithm that prevents high resource utilization and high energy consumption and keeps the process more efficient by following a fair lottery system. The algorithm is often used on the permissioned blockchain networks to decide the mining rights or the block winners on the network.

PoET endeavors to direct the issue of PoS which arbitrary determination of members proposing blocks is expected to guarantee that each member has a reasonable opportunity to offer a block and, in this manner, produce prevalent advantages.

In this, every member asks for a hold-up time from its local reliable enclave. The member with the briefest hold-up time is next to offer a block after it hold-up for the allotted waiting time. Each privately trusted enclave signs the potential and the result so other members can confirm that none has deceived the waiting time.

All things considered, it has been asserted by the people broadcasting PoET that it serves the qualities of PoS.


The last variation from the consensus mechanisms that we will discuss is the Proof of Importance (PoI). The primary cryptographic money platform to execute this was NEM. With PoI, it isn’t just the coin balance that values.

Proof of Importance is the mechanism that is used to determine which network participants (nodes) are eligible to add a block to the blockchain, a process that is known by NEM as ‘harvesting’. In exchange for harvesting a block, nodes are able to collect the transaction fees within that block. Accounts with a higher importance score will have a higher probability of being chosen to harvest a block. In order to be even eligible for the importance calculation, the NEM protocol requires that an account hold at least 10,000 vested XEM in order to be eligible for harvesting.

NEM’s consensus network depends not only the number of coins but on the possibility that productive system action ought to be remunerated. The chances of staking a block are a component of various factors, including notoriety (controlled by a different purpose-designed framework), balance, and the number of transactions made to and from that position. This gives a more all-encompassing image of a ‘helpful’ system member.

These are chosen utilizing a specific algorithm, not just by probability and size of their shares. Likewise, their significance for the system and the significance that the system clearly has for them stream into the procedure. A recognition of fake use and manipulative models is, obviously, included in this idea to avoid spammy members to pick up a higher importance score.

Furthermore, just a particular sort of stake is considered for the mechanism to be considered as possessions. Coins in the NEM wallet are not considered as wealth until the point that they are vested. 10% of the un-vested coins for every 24 hours will be charged to this vested wallet. Accordingly, members get an incentive to make just vital transactions and can just increment the importance score gradually by demonstrating their association with the system.

Blockchain networks that utilize PoS incorporate Nem, Dash, and Peercoin. Likewise, Ethereum is thinking to move its protocol from PoW to PoS when it embraces its Casper network.

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Blockchain research analyst at Nvest Labs
Graduated as a Computer Science engineer from VTU in 2017. Currently pursuing my Masters in Software Engineering from University of Visvesvaraya College of Engineering (2017-19 batch). Interning as Blockchain research analyst at Nvest Labs.
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