45 votes
Accepted

Why doesn't Bitcoin migrate to proof-of-stake?

Proof of Stake is basically a case of having your cake and eating it, too. PoW is a simple work-around to a coordination problem that was previously thought to be unsolvable. It sort of "cheats&...
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  • 63.5k
21 votes

Why doesn't Bitcoin migrate to proof-of-stake?

I think there are at least four reasons: The miners are stakeholders in the bitcoin ecosystem. Mining solves a problem for them. Taking away PoW mining would make bitcoin no longer work for one of ...
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20 votes
Accepted

How does proof of work inspire trust when the work is just guessing?

Forget PoW for a second: lets instead imagine that you have a box, and you've placed a lock on it, in order to secure its contents. Now, if someone asks you how secure the contents are, then the ...
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  • 17.3k
14 votes

Why do we need Proof of Work in bitcoin?

Proof of Work (PoW) basically makes sure that miners don’t cheat. There is no way to trust that everyone in the network is honest, so there has to be some way to prevent miners from creating new ...
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  • 141
14 votes

Why doesn't Bitcoin migrate to proof-of-stake?

I think there are some very convincing theoretical arguments to be made, but there is also just a very practical consideration: Right now, a very large portion of BTC is being held in the cold ...
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  • 17.3k
12 votes

Is there a way to set up proof-of-work systems so they would be even more useful?

Assume for a second that we found a proof of work algorithm that had all of the good properties of sha256, but was also useful for SETI and maintaining world peace. Now suppose a group of miners ...
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  • 431
12 votes
Accepted

Why do we need Proof of Work in bitcoin?

Imagine I have 1 bitcoin. And imagine I can form a transaction to send that bitcoin to Alice or I can form a transaction to send that bitcoin to Charlie. Now, what stops me from forming both ...
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11 votes
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Probablity Distribution of mining

The time between consecutive blocks follows the exponential distribution, with mean (roughly) 10 minutes. This means that the variance is 100 minutes^2.
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11 votes
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What Value does mining provide?

As you mentioned, bringing coins into the network is one of the main purposes of mining. But this reward is just an incentive to do the other more important part of mining: 'processing' transactions. ...
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  • 13.7k
11 votes
Accepted

Does proof-of-work contribute directly to prevent double-spending?

There are multiple definitions of the term "double spending" at play here. First, there is the actual definition of double spending: to spend the same money multiple times. A simple example of this is ...
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  • 61.4k
10 votes

What other whitepapers are there for coin distribution models like POW (proof of work) and POS (proof of stake)?

I don't know of any such list yet, but no reason we can't start making one. :) Others should feel free to add their findings via an edit. Proof of Work Proof of Stake Proof of Activity Proof of ...
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  • 13.7k
10 votes
Accepted

What prevents similar time-warp attacks in Bitcoin as happened to Verge?

Nothing directly prevents it in Bitcoin, and indeed the attack has been demonstrated on testnet3 many times---it's the primary reason that testnet3 currently has almost three times as many blocks as ...
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10 votes

Is proof-of-work required in Bitcoin?

Proof of work does not create trust. It creates incentive. Miners are paid if their block is eventually part of the main version of history ("blockchain") that the network accepts. They must ...
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10 votes
Accepted

Why is the winner of Pow different everytime?

Because each miner may select the transactions (and the order in which they are included) in each block. Also, they do not all start on the same exact nonce, in fact they are changing more than just ...
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  • 7,060
9 votes

Beginner's question: Why must proof-of-work be useless?

In addition to the technical factors mentioned by MCCCS, it's important to consider economical factors as well. If the problem being solved has value outside of the Bitcoin network, it allows miners ...
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  • 16.5k
8 votes
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What's the difference between PoW and PoS?

The following points try to simplify/abstract: A cryptocurrency has its own blockchain to store all the transactions that occurred. A proof of work/stake algorithm are different methods (or ...
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  • 2,204
8 votes

If SHA256 produces an alphanumeric hash, how can a hash be "less than a certain value"?

Not that other answers are wrong here, but just to approach your confusion from another angle: SHA256 hashing algorithm, which produces alphanumeric hashes. That's not true. The hashing algorithm ...
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  • 6,189
8 votes

51% attack and rewriting to the latest checkpoint

As long as both competing chain-tips are adhering to the same rules, the chain with the most aggregate difficulty ("heavier") will win, regardless of height. Nodes performing the initial sync would ...
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  • 63.5k
8 votes
Accepted

Is Bitcoin PoW actually SHA256 + Merkle generation? Or have I misunderstood coinbase/append?

You are correct that effectively Bitcoin PoW involves computing the Merkle root every now and then in addition to the hash grinding. However, this is negligable. Even ignoring nTime rolling, the ...
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8 votes

How does a blockchain relying on PoW verify that a hash is computed using an algorithm and not made up by a human?

A Hash Function maps "data of arbitrary size to fixed-size values". As an incredibly simple hash, consider a function only works on numbers and simply returns the last 3 (decimal) digits (ie....
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  • 181
7 votes

Who are you solving algorithms for and why?

The algorithm of choice is two rounds of SHA256, which has completely arbitrary outputs and a massively unsearchable output space. To this end, there is no data mining or valuable calculation actually ...
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  • 14.3k
7 votes

Why can't we design a bitcoin that does useful work?

In addition to PrimeCoin, there was also PermaCoin proposed as a solution to archival of public knowledge: Excerpt from the abstract: We propose a modification to Bitcoin that repurposes its ...
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7 votes

Probablity Distribution of mining

The expected time (mean) for a new block is of course 10 minutes, assuming constant hashrate, and no block propagation time. The tricky part is that there is no such thing as a point in time. You can ...
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7 votes
Accepted

Why does an adversary have to control 50% of the computing power to double spend?

There are two assumptions in your question that aren't completely correct. 1) Each node would then require 68 minutes to find a proof of work (trying 2^52 hashes). The process of finding a new block ...
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  • 63.5k
7 votes
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What is the most lightweight proof-of-work algorithm?

Contrary to the name the proof of work used in Litecoin is significantly more difficult than SHA256 to verify (it slows sync times noticeably), while simultaneously not achieving it's goals of being ...
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  • 15k
7 votes
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Why was finding a hash beginning with a certain number of zeroes chosen as the proof of work?

It reuses the HashCash construct invented by Adam Back (a scheme for proving work was done to send an email, resulting in it being treated as less spammy by spam filters), though with a newer hash ...
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7 votes
Accepted

How does Proof of Burn work?

Attention: Ambiguity! Note that the term (or abbreviation) "PoB" can be used differently. For example, some cryptocurrencies allow users to get some of their coins for provably burning money in ...
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  • 3,154
7 votes
Accepted

Chain with most proof of work - hash target or block header hash?

It's the sum of difficulty targets, not the individual difficulty scores. Therefore, two blocks at the same blockchain height are always the same cumulative difficulty¹. If it were individual ...
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  • 63.5k
7 votes

Why don't the miners just take profit from our coins and make the coin worthless?

Because miners do not actually own/ or have access to the bitcoins which are being spent in a transaction. They simply choose a number of transactions which have valid signatures, and put them ...
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7 votes
Accepted

PoW 51% attack vs. BFT 1/3 attack?

So from what I understand, Bitcoin's PoW is prone to 51% attack, but as a distributed system it is also prone to BFT's 1/3 attack right? No. Bitcoin is not a "consensus system" by any of the ...
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