I have read and I vaguely understand about how Proof of Work works and what does it do. But why PoW?

Or more bluntly, why do we need any algorithm at all to add new blocks.

What would happen if there wasn't any PoW algorithm in place?

If someone has any ref. links that would help me understand this better, please share.

Thanks in advance.


In this context, "consensus" means agreement about transaction order, not the state.

In case it is not clear, nodes can agree on the result after they agree on transaction order because they can work out, independently, what the state must be. It's similar to a replay log that enables reconstruction of a database.

Nodes learn about proposed transactions at different times due to network latency. Given that no one's clock is any more authoritative than anyone else's in a decentralized system, timestamps are not a solution to transaction order. If the goal is that no node is more authoritative than any other, how then to assign the privilege of deeming the contents of each block?

PoW makes it computationally expensive to gain outsized influence over the system. It can be thought of as a resiliently randomized election process. PoS is an alternative method that attempts to accomplish similar goals with improved performance.

Hope it helps.


It depends on what would be in the place of PoW. There has to be some logic/algorithm.

PoW and consensus are closely related: consensus needs some mechanism to limit the block production and in Ethereum it's currently PoW.

If everyone was allowed to add blocks to the blockchain at will it would be very hard to reach consensus as basically every node would form its own (possibly long) sub-chain. Currently consensus is reached by always taking the heaviest (almost the same as longest) chain as the canonical chain - the heavier it is the more nodes have put effort into it and therefore the more secure it is.

There are many alternatives to PoW and all have their pros and cons. Here are a few examples: https://hackernoon.com/beginners-guide-what-s-the-difference-between-proof-of-work-proof-of-stake-proof-of-burn-and-74c42df591ca

  • Okay. So, the intention is to limit the block production. But in that case, any set of systems which have higher compute capacity can join the network and add their own preferred blocks in the chain. – aash Sep 25 '19 at 9:59
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    If you have more computing capacity than 50% of the network then yes, you can join and add whatever blocks you wish. If you only possess for example 10% of the capacity it means you only get to add every 10th block, or so. But the blocks still need to be valid. – Lauri Peltonen Sep 25 '19 at 10:13

Because of the open, public and decentralized nature of blockchain, there exists no scope for authenticating the participants in the blockchain network. It becomes difficult to guarantee the legitimacy and genuineness of a participating entity.

The proof-of-work (PoW) mechanism solves this problem by exploiting the characteristics of practical resource-intensive operations also known as mining used for solving a complex mathematical problem. A participant or the miner needs to do the computations in real to add his proposed block to the blockchain. There, exists no shortcuts for solving the problem. The solution for the problem obtained by the miner is the proof that the participant has actually performed the operations and is a genuine, not a malicious one.

Answer to Point 2 and 3: The PoW consensus algorithm is the best and time tested consensus algorithm used to reach a consensus in a public blockchain. There exists other blockchain consensus algorithms but they lack in scalability in terms of the number of nodes and are much more prone to be exploited by attackers leading to centralization of block generation. The Bitcoin blockchain(the most matured blockchain) also relies on PoW for reaching a consensus. The only case when the algorithm will fail is when a malicious participant will have control over >50% of the computing resources in the blockchain network, which is practically not feasible for anyone to have.

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