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Why does Ethereum plan to move to Proof of Stake?

The fundamental flaw of Proof of Work (PoW) is that the costs of attacking the system are equal to what is spent to run the system. High security thus can only be achieved at high operating costs. The ...
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100 votes
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What happens when a transaction nonce is too high?

Summary Transactions with too low a nonce get immediately rejected. Transactions with too high a nonce get placed in the transaction pool queue. If transactions with nonces that fill the gap between ...
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64 votes

Why does Ethereum plan to move to Proof of Stake?

There are two key motivations for the move to Proof of Stake: Ethereum developers and researchers believe that consensus algorithms based on Proof of Stake (PoS) can provide a higher degree of ...
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58 votes

What is an uncle/ommer block?

Uncles are stale blocks that contribute to the security of the main chain, but are not considered the canonical "truth" for that particular chain height. In contrast to orphan blocks (which have no ...
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57 votes
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Why is the average block time 17 seconds?

Due to advances in blockchain research, it was shown that significantly lower block times were possible and perhaps beneficial given the current connectivity of the internet. One of the potential ...
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54 votes
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What proof of work function does Ethereum use?

The PoW algorithm used in Frontier and Homestead is called Ethash, and it was created specifically for Ethereum. The primary reason for constructing a new proof of work function instead of using an ...
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  • 20.9k
53 votes

What's the difference between proof of stake and proof of work?

Let us start by what they have in common: they are both algorithms for reaching consensus on the blockchain. Without going into too much details, we need consensus because anyone can create a block; ...
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  • 1,334
50 votes
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What is an uncle/ommer block?

From the glossary Uncle: a child of a parent of a parent of a block that is not the parent, or more generally a child of an ancestor that is not an ancestor. If A is an uncle of B, B is a nephew of ...
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  • 5,808
37 votes
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What exactly is an Ethereum client and what clients are there?

An 'Ethereum client' is just a term. It refers to any node able to parse and verify the blockchain, its smart contracts and everything related. It also allows you/provides interfaces to create ...
33 votes

Why does Ethereum plan to move to Proof of Stake?

That is very complicated topic. Considered Proof-of-Work waste energy to maintain security of a public censorship resistant consensus ledger. Though there is a long standing debate about this point. ...
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31 votes
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What's the difference between proof of stake and proof of work?

The goal of a consensus algorithm in a public blockchain network is to let many different users agree on the current state of the blockchain even though they don't trust each other or any central ...
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  • 20.9k
30 votes

What was the reason to invent the EVM?

Vitalik Buterin gave a presentation about Ethereum to Hyperledger April 28 2016 and had this slide: EVM Requirements ● Small code size (so that very many contracts from many users can be stored by one ...
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  • 78k
26 votes

How does the Casper proof of stake algorithm work?

The friendly Ghost Casper is a security-deposit based economic consensus protocol. This means that nodes, so called bonded validators, have to place a security deposit, an action called bonding, in ...
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24 votes
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What was the reason to invent the EVM?

So the important point in your question is why a new VM and not a java VM. ok let's choose a Java VM instead, what do we get? : 1- complex and voluminous Bytecode => how to store it, in the ...
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  • 17.4k
21 votes
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Is Ethereum secure against an attack by quantum computers?

Currently, Ethereum uses elliptic curve cryptography, which is not quantum resistant. In the upcoming Serenity upgrade, however, accounts will be able to specify their own scheme for validating ...
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  • 33.9k
21 votes
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Does every node execute the contract code for each transaction?

Yes, the answer is quite logic. Every node has to verify the results of a transaction which invokes a smart contract. The result is that at least every full node will execute the code. The hash of ...
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  • 31.3k
19 votes
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How many transactions per second can Ethereum currently handle? What changes will allow the network to be able to handle more?

I did the math to show the aprox tx/s: The block gas limit is 7,999,992 Transaction costs 21,000 gas (let's assume nothing else is attached) That's ~380 transactions per block With a block time of ...
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  • 2,735
16 votes
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What is casper?

There are a number of reasons I much prefer Casper over PoW: In PoW, any coalition of >50% (or 25-33% if selfish mining) can very profitably censor and revert history. In Casper, it takes close to ...
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15 votes

What exactly is an Ethereum client and what clients are there?

There are a couple of "reference implementations" that the Ethereum foundation is supporting. Ethereum C++ (known as Eth or "TurboEthereum") Go Ethereum (known for the command line client Geth) ...
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  • 1,765
14 votes
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During a 51% attack, What Can the Attacker Actually Accomplish?

In a temporary 51% attack, the attacker can: censor or reorder transactions at will (i.e. prevent you from using your money or any dApps) doublespend ether/tokens/shares at will to drain non-...
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  • 20.9k
13 votes

What's the difference between proof of stake and proof of work?

Short version - POW requires miners or physical computer to be turned on and processing the transaction. This can be inefficient since better computers are created and optimized for mining which may ...
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  • 4,598
13 votes

Does every node execute the contract code for each transaction?

Every full node processes every transaction. The miners choose which transactions to execute, based on gasprice. Once a block is mined, every node must rerun all of the contract executions in order to ...
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  • 33.9k
13 votes
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When there is an unexpected hardfork, what is the procedure taken by the core team?

We've had an unexpected fork in the past that caused a split between clients. While no hardfork is like any hardfork we generally follow these rules and steps: Identify and announce the issue; Create ...
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  • 1,889
12 votes
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What is GHOST and what is its relationship to Frontier and Casper?

GHOST is short for the Greedy Heaviest Observed Subtree chain selection rule which was a proposed modification for the Bitcoin blockchain (Paper). GHOST orignally was a protocol modification, a chain ...
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  • 31.3k
11 votes
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Bitcoin : Ethereum :: Raft : Paxo

No; Ethereum and Bitcoin's consensus algorithm is very different from Raft and Paxos. Ways in which they differ: In both Raft and Paxos, the systems elect a leader. There is no leader in Ethereum and ...
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  • 6,540
10 votes

How does the Casper proof of stake algorithm work?

https://gitter.im/ethereum/research is an open, highly technical channel where the most details about Casper can be obtained currently. Here are some background references that can help before ...
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  • 78k
10 votes

What is casper?

A different explanation of Casper was written by Vlad. Some of the points from the post include: It is an eventually-consistent blockchain-based consensus protocol It favours availability over ...
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10 votes

What does it mean to "seal a block"?

"Seal a block" is a proposed term to describe "mine a block" in a private chain. Private chains typically do not need to use proof-of-work mining, so a different term can be helpful. Specifics of ...
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  • 78k
10 votes
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QuorumChain Consensus vs Raft Consensus vs Istanbul consensus quorum

I'm not an expert on this Quorum world. But as i've read, the main difference between the three mechanisms you mentioned is the % of BFT (Byzantinism Fault Tolerance). BFT is defined as: ...
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  • 2,735
9 votes
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How can I compare two consensus protocols?

There are several different ways to answer this question. For example, you could try to measure the percentage of the network that must misbehave in a malicious or "byzantine" manner before agreement ...
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  • 20.9k

Only top scored, non community-wiki answers of a minimum length are eligible