<p><strong>The short answer is yes, PoW is an indispensable component in blockchain.</strong></p>
<p>First, let's discuss whether Bitcoin's <strong>proof-of-work-chain</strong> can be considered a consensus mechanism.</p>
<p>The article proposing the Bitcoin network concludes with the idea that the <strong>“proof-of-work-chain”</strong> consists of two parts: the proof-of-work mechanism and the chaining process, and this combination can be seen as a consensus mechanism.</p>
<p><a href="https://i.sstatic.net/zO4RskG5.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zO4RskG5.png" alt="enter image description here" /></a></p>
<p>However, Bitcoin’s <strong>“proof-of-work-chain”</strong> mechanism does not fully satisfy the '<strong>Agreement</strong>' condition required for consensus mechanisms.</p>
<p>In Bitcoin’s <strong>“proof-of-work-chain”</strong>, temporary forks can occur, especially during the creation of new blocks. Miners might find valid solutions to the cryptographic puzzle simultaneously, resulting in competing valid blocks. This leads to different parts of the network initially supporting different blocks.</p>
<p>While the network eventually converges to a single chain, and the longest-chain rule determines the canonical blockchain, there are brief periods when consensus is not unanimous, and different nodes might temporarily support different blocks. This temporary fork phenomenon is inherent in the probabilistic nature of Bitcoin’s proof-of-work mechanism.</p>
<p>The debate on whether the combination of proof-of-work and the chaining process in Bitcoin constitutes a consensus mechanism remains unsettled. The Bitcoin network mechanism does not fulfill all conditions of a consensus mechanism, which include Termination, Uniform Integrity, Agreement, and Uniform Validity. <em><strong>[citation]</strong></em></p>
<p><em><strong>[citation]</strong> Kshemkalyani, Ajay D., and Mukesh Singhal. Distributed computing: principles, algorithms, and systems. Cambridge University Press, 2011.</em></p>
<p>It is important to note that the designers of the Bitcoin network proposed the 'proof-of-work-chain' as a consensus mechanism, implying the combination of proof-of-work with the chaining process, not proof-of-work alone.</p>
<p><strong>Therefore, the early term 'proof-of-work-chain' might be more accurate than 'blockchain,' as it emphasizes the integration of proof-of-work and the chaining process. Separating these two elements affects the entire network, including the effectiveness of the chaining process without proof-of-work.</strong></p>
<p>Without PoW, the connected blocks can be entirely replaced by an altered chain. This is true whether there is a lack of a Sybil or DoS attack prevention mechanism—such as a sufficiently difficult proof-of-work proportional to the total hashing power of the network—or in a permissioned network.</p>
<p>In the absence of PoW, it is possible to replace the entire blockchain with a new valid one, where all blocks are generated based on the hash of previous blocks, thereby creating and replacing the existing blockchain with a new valid chain.</p>
<p><strong>Therefore, yes, PoW is an indispensable component in blockchain</strong></p>
<p><strong>A blockchain system without PoW does not make sense for preventing the alteration of transaction history.</strong></p>
<p>This is despite Bitcoin's proof-of-work-chain having its own problems and inefficiencies, such as consuming a large amount of energy while processing only 7 to 10 transactions per second.</p>
<p><strong>Important Note 1:</strong>
It is incorrect to argue that since Ethereum no longer uses PoW, a blockchain without PoW is also meaningful. The blockchain structure does not contribute to the security of Ethereum after the removal of PoW. In the current version of Ethereum, security is provided by other parameters and elements. Over time, this will become clear.</p>
<p><strong>Important Note 2:</strong>
I'm aware that many blockchain platforms simply chain stored data, which is why I started this discussion. Without sufficiently difficult PoW, if someone can manipulate one block, they can manipulate the rest. Conversely, if they can't manipulate even one block, it is not due to the &quot;chained blocks&quot;. However, this is not the case with PoW_Chain. The inability to manipulate the blocks in PoW_Chain is due to the existence of PoW with a sufficient level of difficulty. In PoW_Chain, someone might be able to manipulate one block but not two blocks, and this is due to the &quot;chained PoWs&quot;.</p>
<p><strong>Additional information and explanations:</strong></p>
<ol>
<li><a href="https://www.researchgate.net/publication/381187113_Narrated_PowerPoint_presentation_of_the_PhD_thesis/stats" rel="nofollow noreferrer"><strong>A Narrated PowerPoint (Click on the link)</strong></a></li>
<li><a href="https://www.researchgate.net/publication/379148513_Novel_Fault-Tolerant_Self-Configurable_Scalable_Secure_Decentralized_and_High-Performance_Distributed_Database_Replication_Architecture_Using_Innovative_Sharding_to_Enable_the_Use_of_BFT_Consensus_Mec" rel="nofollow noreferrer"><strong>A PhD Dissertation (Click on the link)</strong></a></li>
<li><a href="https://www.youtube.com/watch?v=EhBHfQILX1o" rel="nofollow noreferrer"><strong>A Video Presentation (Click on the link)</strong></a></li>
<li><a href="https://www.researchgate.net/publication/349537863_Permissioned_vs_Permissionless_Blockchain_How_and_Why_There_Is_Only_One_Right_Choice" rel="nofollow noreferrer"><strong>Permissioned vs. Permissionless Blockchain: How and Why There Is Only One Right Choice (Click on the link)</strong></a></li>
</ol>

CC BY-SA 4.0
2024-06-13T18:29:00.263Z
Unfortunately, [opinion is off-topic on bitcoin.se](https://bitcoin.stackexchange.com/help/dont-ask).  We (the moderators, and content curators) make a point of ensuring questions are on-topic, and the answers to those questions, are provably correct.  Opinion really has no place here.
Hannah Vernon
CC BY-SA 4.0
2024-06-13T00:10:55.387Z
2024-06-19T15:13:29.533Z
2024-06-19T15:13:29.533Z
Questioner
<p>&quot;blockchain&quot;, as used in your question without qualification, is an underspecified term. It can be, and is, used to refer to:</p>
<ul>
<li>The blockchain data structure used in various specific cryptocurrencies.</li>
<li>The consensus algorithm used in various specific cryptocurrencies.</li>
<li>A collective term for a whole industry based on vaguely related technology.</li>
<li>A buzzword to put on marketing slides.</li>
</ul>
<p>So let me answer more specific versions of your question in the title:</p>
<ul>
<li><strong>Is PoW an essential part of the Bitcoin blockchain data structure?</strong> The data structure does contain fields relating to proof-of-work, but those could be removed without breaking the data structure itself.</li>
<li><strong>Is PoW an essential part of the Bitcoin consensus algorithm?</strong> Absolutely. It provides the economic incentive for convergence, it provides denial-of-service protection, and indirectly controls the rate of subsidy dispensing. Certainly each of these components could be replaced with different technologies, but the result would lack the properties that Bitcoin has.</li>
<li><strong>Is PoW an essential part of every cryptocurrency consensus algorithm?</strong> Obviously not, as there are plenty of cryptocurrencies that do not use PoW. Clearly they provide different (and, in my view, inferior) properties, but without qualification about which blockchains you are asking about, it may or may not be treated as a necessity.</li>
<li><strong>Is PoW an essential part of the 'blockchain' industry</strong>? Most &quot;blockchain industry&quot; systems do - to the extent they are still around - not use proof of work.</li>
<li><strong>Is PoW helpful for marketing</strong>? These days, it appears that terms like &quot;AI&quot; and &quot;Staking&quot; are more popular.</li>
</ul>

CC BY-SA 4.0
2024-06-18T19:23:27.837Z
@Hannah Vernon, Continue censorship by deleting my comments in a "decentralized manner"... I might need to write my comments on the "immutable" Bitcoin blockchain...
Questioner
CC BY-SA 4.0
2024-06-18T23:04:52.667Z
@Hannah Vernon , Unfortunately you are not able to understand a simple sentence. The statement "I prefer a PoW-based blockchain" is quite different from the statement "Without PoW, the blockchain data structure does nothing to prevent the stored data from being tampered with."
Questioner
CC BY-SA 4.0
2024-06-19T02:38:11.503Z
I think most users here agree that proof of work is superior to other consensus mechanisms. The issues people seem to have with your answer are that they disagree with the absolute statements and the terminology
Murch
CC BY-SA 4.0
2024-06-12T21:39:36.303Z
2024-06-12T21:39:36.303Z
Pieter Wuille
<p>There is an argument that if the Proof-of-Work (PoW) mechanism is removed from the Bitcoin network or if the puzzle does not have a sufficient level of difficulty proportional to the computing power of the network, the chaining of transactions and blocks will not be effective in preventing the alteration of historical transactions. This is because without a sufficiently difficult proof-of-work proportional to the total hashing power of the network the entire blockchain can be replaced by a new valid blockchain, where each block is created based on the hash of the previous blocks.</p>
<p>Based on this argument, can we say that PoW is an indispensable component in blockchain?</p>

CC BY-SA 4.0
2024-06-13T21:56:13.340Z
You should make it clear when posting links to other platforms, or mention a product or company that you have a relationship with, otherwise you risk being perceived as a spammer.  Feel free to publish all you want on whatever platform you desire, but when posting on Stack Exchange sites, linking to other sites for the purpose of promotion without explicitly calling out the affiliation is against policy.
Hannah Vernon
<blockchain><hash><blockchain-fork><proof-of-work><consensus>
Is PoW an indispensable component in blockchain?
Questioner
# Is PoW an indispensable component in blockchain?

(Asked by: username_0 on 2024-06-12)

There is an argument that if the Proof-of-Work (PoW) mechanism is removed from the Bitcoin network or if the puzzle does not have a sufficient level of difficulty proportional to the computing power of the network, the chaining of transactions and blocks will not be effective in preventing the alteration of historical transactions. This is because without a sufficiently difficult proof-of-work proportional to the total hashing power of the network the entire blockchain can be replaced by a new valid blockchain, where each block is created based on the hash of the previous blocks.

Based on this argument, can we say that PoW is an indispensable component in blockchain?

**Tags:** blockchain, hash, blockchain-fork, proof-of-work, consensus

> **Comments:**
> **username_1**: You should make it clear when posting links to other platforms, or mention a product or company that you have a relationship with, otherwise you risk being perceived as a spammer.  Feel free to publish all you want on whatever platform you desire, but when posting on Stack Exchange sites, linking to other sites for the purpose of promotion without explicitly calling out the affiliation is against policy.  

---

## 2 answers

### Answer by username_0 on 2024-06-13. Score: -4 | Accepted answer

**The short answer is yes, PoW is an indispensable component in blockchain.**

First, let's discuss whether Bitcoin's **proof-of-work-chain** can be considered a consensus mechanism.

The article proposing the Bitcoin network concludes with the idea that the **“proof-of-work-chain”** consists of two parts: the proof-of-work mechanism and the chaining process, and this combination can be seen as a consensus mechanism.

[![enter image description here](https://i.sstatic.net/zO4RskG5.png)](https://i.sstatic.net/zO4RskG5.png)

However, Bitcoin’s **“proof-of-work-chain”** mechanism does not fully satisfy the '**Agreement**' condition required for consensus mechanisms.

In Bitcoin’s **“proof-of-work-chain”**, temporary forks can occur, especially during the creation of new blocks. Miners might find valid solutions to the cryptographic puzzle simultaneously, resulting in competing valid blocks. This leads to different parts of the network initially supporting different blocks.

While the network eventually converges to a single chain, and the longest-chain rule determines the canonical blockchain, there are brief periods when consensus is not unanimous, and different nodes might temporarily support different blocks. This temporary fork phenomenon is inherent in the probabilistic nature of Bitcoin’s proof-of-work mechanism.

The debate on whether the combination of proof-of-work and the chaining process in Bitcoin constitutes a consensus mechanism remains unsettled. The Bitcoin network mechanism does not fulfill all conditions of a consensus mechanism, which include Termination, Uniform Integrity, Agreement, and Uniform Validity. ***[citation]***

***[citation]** Kshemkalyani, Ajay D., and Mukesh Singhal. Distributed computing: principles, algorithms, and systems. Cambridge University Press, 2011.*

It is important to note that the designers of the Bitcoin network proposed the 'proof-of-work-chain' as a consensus mechanism, implying the combination of proof-of-work with the chaining process, not proof-of-work alone.

**Therefore, the early term 'proof-of-work-chain' might be more accurate than 'blockchain,' as it emphasizes the integration of proof-of-work and the chaining process. Separating these two elements affects the entire network, including the effectiveness of the chaining process without proof-of-work.**

Without PoW, the connected blocks can be entirely replaced by an altered chain. This is true whether there is a lack of a Sybil or DoS attack prevention mechanism—such as a sufficiently difficult proof-of-work proportional to the total hashing power of the network—or in a permissioned network.

In the absence of PoW, it is possible to replace the entire blockchain with a new valid one, where all blocks are generated based on the hash of previous blocks, thereby creating and replacing the existing blockchain with a new valid chain.

**Therefore, yes, PoW is an indispensable component in blockchain**

**A blockchain system without PoW does not make sense for preventing the alteration of transaction history.**

This is despite Bitcoin's proof-of-work-chain having its own problems and inefficiencies, such as consuming a large amount of energy while processing only 7 to 10 transactions per second.

**Important Note 1:**
It is incorrect to argue that since Ethereum no longer uses PoW, a blockchain without PoW is also meaningful. The blockchain structure does not contribute to the security of Ethereum after the removal of PoW. In the current version of Ethereum, security is provided by other parameters and elements. Over time, this will become clear.

**Important Note 2:**
I'm aware that many blockchain platforms simply chain stored data, which is why I started this discussion. Without sufficiently difficult PoW, if someone can manipulate one block, they can manipulate the rest. Conversely, if they can't manipulate even one block, it is not due to the "chained blocks". However, this is not the case with PoW\_Chain. The inability to manipulate the blocks in PoW\_Chain is due to the existence of PoW with a sufficient level of difficulty. In PoW\_Chain, someone might be able to manipulate one block but not two blocks, and this is due to the "chained PoWs".

**Additional information and explanations:**

1. [**A Narrated PowerPoint (Click on the link)**](https://www.researchgate.net/publication/381187113_Narrated_PowerPoint_presentation_of_the_PhD_thesis/stats)
2. [**A PhD Dissertation (Click on the link)**](https://www.researchgate.net/publication/379148513_Novel_Fault-Tolerant_Self-Configurable_Scalable_Secure_Decentralized_and_High-Performance_Distributed_Database_Replication_Architecture_Using_Innovative_Sharding_to_Enable_the_Use_of_BFT_Consensus_Mec)
3. [**A Video Presentation (Click on the link)**](https://www.youtube.com/watch?v=EhBHfQILX1o)
4. [**Permissioned vs. Permissionless Blockchain: How and Why There Is Only One Right Choice (Click on the link)**](https://www.researchgate.net/publication/349537863_Permissioned_vs_Permissionless_Blockchain_How_and_Why_There_Is_Only_One_Right_Choice)

> **Comments:**
> **username_1**: Unfortunately, [opinion is off-topic on bitcoin.se](https://bitcoin.stackexchange.com/help/dont-ask).  We (the moderators, and content curators) make a point of ensuring questions are on-topic, and the answers to those questions, are provably correct.  Opinion really has no place here.  

---

### Answer by username_2 on 2024-06-12. Score: 6

"blockchain", as used in your question without qualification, is an underspecified term. It can be, and is, used to refer to:

* The blockchain data structure used in various specific cryptocurrencies.
* The consensus algorithm used in various specific cryptocurrencies.
* A collective term for a whole industry based on vaguely related technology.
* A buzzword to put on marketing slides.

So let me answer more specific versions of your question in the title:

* **Is PoW an essential part of the Bitcoin blockchain data structure?** The data structure does contain fields relating to proof-of-work, but those could be removed without breaking the data structure itself.
* **Is PoW an essential part of the Bitcoin consensus algorithm?** Absolutely. It provides the economic incentive for convergence, it provides denial-of-service protection, and indirectly controls the rate of subsidy dispensing. Certainly each of these components could be replaced with different technologies, but the result would lack the properties that Bitcoin has.
* **Is PoW an essential part of every cryptocurrency consensus algorithm?** Obviously not, as there are plenty of cryptocurrencies that do not use PoW. Clearly they provide different (and, in my view, inferior) properties, but without qualification about which blockchains you are asking about, it may or may not be treated as a necessity.
* **Is PoW an essential part of the 'blockchain' industry**? Most "blockchain industry" systems do - to the extent they are still around - not use proof of work.
* **Is PoW helpful for marketing**? These days, it appears that terms like "AI" and "Staking" are more popular.

> **Comments:**
> **username_0**: @username_1, Continue censorship by deleting my comments in a "decentralized manner"... I might need to write my comments on the "immutable" Bitcoin blockchain...  
> **username_0**: @username_1 , Unfortunately you are not able to understand a simple sentence. The statement "I prefer a PoW-based blockchain" is quite different from the statement "Without PoW, the blockchain data structure does nothing to prevent the stored data from being tampered with."  
> **username_3**: I think most users here agree that proof of work is superior to other consensus mechanisms. The issues people seem to have with your answer are that they disagree with the absolute statements and the terminology  

---

