The Myth that Proof of Work creates Irreversibility
![](https://steemitimages.com/640x0/http://forklog.net/wp-content/uploads/2015/10/pospow.png)
Proof of Work does not make a blockchain irreversible. Many people have made this claim to me during recent interviews. They stated it with such certainty that I didn’t dare correct them on the spot.
I believe this myth has its origin in the defense of proof of work relative to proof of stake blockchains. The argument is that without proof of work anyone could rewrite the history of the blockchain. The erroneous conclusion is that proof of work makes the blockchain irreversible.
What Makes it Irreversible
There are three things that make a blockchain irreversible:
- hash-linked blocks
- public record
- public opinion
The reality is that blockchain irreversibility comes from a public broadcast where many independent observers have recorded the same events. These events are hash-linked which means the public cannot change one event without changing everything that happened after it. If someone wants to change the history, then everyone would see it is a change. Public opinion would be firmly behind the original order of events because any other history would be a lie.
You will notice that there is no need for computationally expensive proof of work to ensure the record is irreversible. You just need enough independent parties who agree on a common history.
Immutable is independent from Irreversible
A blockchain may log all events into an immutable record, but a record is meaningless on its own. What gives a record value is people’s opinion and perception. This means that people can choose to ignore or reinterpret the ledger without actually changing the ledger.
Ethereum is Reversing Transactions
The fact that Ethereum, a proof of work blockchain, is reversing the effects of a transaction is proof that having an immutable record doesn’t make transactions immutable. The people who use Ethereum have collectively decided to reinterpret the immutable history in such a way that produces a better outcome for almost everyone.
Value of Proof of Work
Proof of work provides an objective metric of value invested (sunk cost). This objective metric can be used to authenticate with high probability that a certain history had the backing of public opinion. Without the backing of public opinion the values represented by the data would be worthless. Hence, proof of work is strong evidence of public opinion, but not absolute proof.
Root of Confusion
This may be the root of the confusion. People are mixing up the evidence with the thing the evidence is proving. This would be like someone claiming that a particular set of finger prints cause murders. A person murders someone, the finger prints are just evidence.
Likewise, public opinion secures immutability and proof of work is just the evidence that someone believed the public opinion placed value on something in the past.
Who needs ETH? This entire project is amazing! I can't get off Steemit to do actual work.... whats the point? LOL
"The people who use Ethereum have collectively decided to reinterpret the immutable history in such a way that produces a better outcome for almost everyone."
This is what people don't seem to understand around their subreddits... I can't understand the whole panic selling price changes that happened after the Dao "hack", either bitcoiners are really good at spreading FUD or just manipulation and weak hands. When will people learn that these cryptocurrencies aren't some "get rich quick" scheme. Time pays off.
or the outcome could be worse for almost everyone when there is no more trust in the original promises of the system.
Some people confuse the map with the location. That's what I thought of what I read your explanation. This may also impact thinking about hard limits such as the number of mineable coins or the number of decimal points of precision. Ultimately, if enough people want it, it'll happen (either with a hard fork, rebranding, or voted for and agreed upon code change, etc). To me, that's the beauty of crypto. A mechanism for determining consensus where each actor works in their own self interest which happens to align with the interests of the entire group, all without coercion.
I remember watching Bitcoin in March 2013 as consensus was reached around the world to prevent a true hard fork. It was amazing to see, and I've been hooked ever since.
POW is not for creating Irreversibility.
POW is needed in order miners could trust each other. Trustlesness - what is POW for.
https://en.wikipedia.org/wiki/Byzantine_fault_tolerance
Has anyone thought of using a decaying isotope as a physical proof of work? You could tag each transaction with the current state (neutron output) of the radioactive substance. Each transaction would have a unique number, each lower than the next.
You're talking about Litecoin right?
exactly!
Let's fry our power stations with help of Proof-of-Work xD
This article is invalid. Nakamoto consensus implies relative immutability, that is a block N deep in the chain is more immutable than that of block N+1 in the chain. In the proof of stake, the immutability is corrupted trivially, by all stake participants to sign-of multiple histories, or in some cases, to claim that all possible histories have in fact happened. PoS does not prevent this, and thus double spend can, and will occur.
Double spend on steem is impossible. But it is still possible on Bitcoin.
I was initiated into ethereum due to the phrase "code is law" which I took to be the utopia of decentralisation. Unfortunately, I did find out the hard way that public opinion can cause reversal in an otherwise deemed irreversible chain. The incident with the DAO brought me to my senses, but also instilled fear that this has opened up a can of worms which regulatory authorities might jump at. Thereby negating the benefits of decentralisation using such a chain.
Nicely explained, I'd like to read a similar explanation on proof of stake.
CG
And when it will implemented in Ethereum
Proof of Vitalik creates bulletproof investments - either you make money or there is a PoW fork!
Live long and fork.
Did they do the hard fork yet?
It is alien ?!