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46 votes
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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&...
Murch's user avatar
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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 ...
David Schwartz's user avatar
20 votes
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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 ...
chytrik's user avatar
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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 ...
JakeW's user avatar
  • 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 ...
chytrik's user avatar
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12 votes
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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 ...
David Schwartz's user avatar
11 votes
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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 ...
Ava Chow's user avatar
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10 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 ...
Murch's user avatar
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10 votes
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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 ...
David A. Harding's user avatar
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 ...
Pieter Wuille's user avatar
10 votes
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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 ...
JBaczuk's user avatar
  • 7,428
10 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 ...
Raghav Sood's user avatar
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9 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 ...
Jannes's user avatar
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8 votes
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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 ...
Pieter Wuille's user avatar
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....
minnmass's user avatar
  • 181
7 votes
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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 ...
UTF-8's user avatar
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7 votes
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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 ...
Murch's user avatar
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7 votes
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How does a miner get selected in Proof Of Stake?

The minting algorithm for staking is different for various coins; for example, it is different in BlackCoin from Cardano. There are several approaches to staking, but most of them are susceptible to "...
dionyziz's user avatar
  • 1,012
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 ...
Rutger Versteegden's user avatar
7 votes
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In what sense does the security model of proof-of-stake require users to "log on to the internet every few months"

What Vitalik is talking about is the Slasher algorithm that he designed which punishes the block signer if he attempts to create a fork in the blockchain. However the way that slasher works is that ...
Ava Chow's user avatar
  • 71.1k
7 votes
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How does scrypt pow work?

It's the same: the proof-of-work is that the scrypt hash of the block header must start with a certain number of zeros (or, more precisely, be numerically less than a certain target value). However, ...
Nate Eldredge's user avatar
7 votes
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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 ...
G. Maxwell's user avatar
  • 7,727
7 votes

What hash algorithm is used in Bitcoin Cash?

BCH and BSV both use SHA256 as their POW algorithm, as does Bitcoin (BTC).
chytrik's user avatar
  • 18.3k
7 votes

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

Because Everyone can quickly use the transaction data to re-calculate the hash and check that it matches and is less than the target value. Computing the hash is not what takes time, it is altering ...
RedGrittyBrick's user avatar
7 votes

Would Bitcoin still work without a target difficulty?

It's not trivial a) to agree on the time in a distributed system, especially how much time has passed between two events, b) to establish when exactly a block candidate was found. Further, when a node ...
Murch's user avatar
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6 votes
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If SHA256 produces an alphanumeric hash, how can a hash be "less than a certain value"?

The hash is not alphanumeric, it's hexadecimal, that is base-16. You can convert that to a decimal number. In your case: 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 = ...
Jimmy Song's user avatar
  • 7,759
6 votes

Byzantine Fault Tolerance Threshold of Bitcoin: 1/2 or 1/3? (Edited)

It depends on what you're actually asking. Bitcoin doesn't exist within the normal model of BFT consensus so in one sense the answer is mu. Under conventional assumptions Bitcoin will converge on a ...
G. Maxwell's user avatar
  • 7,727
6 votes
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Proof of work - lottery approach

There's a lot going, but I'll do my best. QUESTION: Can the bitcoin network randomly select a subset of the existing nodes, for each block, who then compete to solve the hash? Selecting a subset ...
Tiago Loriato Simões's user avatar
6 votes
Accepted

What would happen if miners refused halving

What if after this phase the first miner or more than 51% of them decide to keep the current production rate ? Do their block will be refused like if they had produced a wrong block ? Exactly. This ...
chytrik's user avatar
  • 18.3k
6 votes
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How much more energy efficient is PoS (proof of stake) than PoW (proof of work)? Are there any figures on this?

When providing an equivalent amount of security, I don't believe PoS can be more efficient than PoW. I do understand how it may appear this way on the surface, but I think deeper consideration shows ...
chytrik's user avatar
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