# Proof-of-Work (PoW)

> Proof-of-Work (PoW) is a consensus mechanism used in blockchain technology, originally implemented by Bitcoin, to validate transactions and prevent fraudulent activity, with miners racing to solve a hard hashing puzzle to add the next block.

- Canonical URL: https://iq.wiki/wiki/proof-of-work-pow
- Categories: Glossary
- Created: 2023-01-24T09:47:40.986Z
- Last updated: 2026-06-18T14:38:04.830Z
- Source: IQ.wiki — the world's largest blockchain and crypto encyclopedia (https://iq.wiki)

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**Proof-of-work (PoW)** is a system used in computer science to validate transactions or computations and to prevent malicious activities such as denial of service attacks. It is the original [crypto](https://iq.wiki/wiki/cryptocurrency) consensus mechanism used to prove that certain calculations have been done and to prevent double-spending. It was first used by [Bitcoin](https://iq.wiki/wiki/bitcoin). [\[4\]](#cite-id-66oq5isbbgf)[\[5\]](#cite-id-2u17y0jgiue)\


# Overview

It is called “proof of work” because the network requires a huge amount of processing power. Proof-of-work blockchains are secured and verified by virtual miners around the world racing to be the first to solve a math puzzle. The winner gets to update the [blockchain](https://iq.wiki/wiki/blockchain) with the latest verified transactions and is rewarded by the network with a predetermined amount of [crypto](https://iq.wiki/wiki/cryptocurrency). [\[3\]](#cite-id-71g94plvwsi)

The purpose of proof of work is to ensure that only legitimate users are able to generate valid solutions and to prevent malicious activities such as double-spending. In [Bitcoin](https://iq.wiki/wiki/bitcoin), proof of work is used to ensure that the [blockchain](https://iq.wiki/wiki/blockchain) remains secure and valid.

The idea for Proof of Work(PoW) was first published in 1993 by Cynthia Dwork[\[6\]](#cite-id-f8yi4i6ugjn) and Moni Naor[\[7\]](#cite-id-oqt826j7udq) and was later applied by [Satoshi Nakamoto](https://iq.wiki/wiki/satoshi-nakamoto) in [Bitcoin](https://iq.wiki/wiki/bitcoin) whitepaper in 2008. The term “proof of work” was first used by Markus Jakobsson[\[1\]](#cite-id-u4drzymp7fm) and Ari Juels[\[2\]](#cite-id-ugw6rzw8gkg) in a publication in 1999. [\[5\]](#cite-id-2u17y0jgiue)

# Technology

[Bitcoin](https://iq.wiki/wiki/bitcoin) is a [blockchain](https://iq.wiki/wiki/blockchain), which is a shared ledger that contains a history of every Bitcoin transaction that ever took place. This blockchain is composed of blocks — each block with the most recent transactions stored in it.\
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Proof-of-work is a necessary part of adding new blocks to the [Bitcoin](https://iq.wiki/wiki/bitcoin) blockchain. Blocks are developed by miners, the players in the ecosystem who execute proof of work. The network accepts a new block each time a miner comes up with a new winning proof of work, which happens roughly every 10 minutes.\
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Finding the winning proof-of-work is difficult and requires expensive, specialized computers. Miners attempt to guess a matching computation and, if successful, will earn bitcoin. The computations they make are known as "hash" which takes an input and produces a random string of letters and numbers.\
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Miners aim to generate a hash that matches Bitcoin's current "target". It requires a hash with a large number of leading zeroes, which is a highly improbable occurrence. Despite this, miners around the world compute trillions of hashes per second, typically taking around 10 minutes to reach the target.\
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Whoever reaches the goal first will be rewarded with a batch of [Bitcoin](https://iq.wiki/wiki/bitcoin) cryptocurrency. The Bitcoin protocol then creates a new value, which miners must hash, and miners compete to find the winning proof-of-work. [\[8\]](#cite-id-ytybi0x1kk)

# Feature of PoW

* It is difficult to find a solution to a mathematical problem.
* It is easy to verify the correctness of that solution. [\[5\]](#cite-id-2u17y0jgiue)

# Challenges With PoW

## The 51% risk

If a controlling entity owns 51% or more than 51% of nodes in the network, the entity can corrupt the blockchain by gaining the majority of the network. [\[5\]](#cite-id-2u17y0jgiue)

## Time-consuming

Miners have to check over many nonce values to find the right solution to the puzzle that must be solved to mine the block, which is a time-consuming process. [\[5\]](#cite-id-2u17y0jgiue)

## Resource consumption

Miners consume high amounts of computing power in order to find the solution to the hard mathematical puzzle. [\[5\]](#cite-id-2u17y0jgiue)

## Non-instantaneous transaction

Transaction confirmation takes about 10–60 minutes. It takes some time to mine the transaction and add it to the [blockchain](https://iq.wiki/wiki/blockchain) thus committing the transaction. [\[5\]](#cite-id-2u17y0jgiue)