Questions tagged [consensus]

Questions about the consensus system of Bitcoin and the protocol rules that are consensus critical.

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49
votes
2answers
22k views

What happens if two miners mine the next block at the same time?

The process of mining as described in the answer to this question is simultaneously repeated by multiple miners. Is it possible for two miners to find the next block at the same instant? If it is, ...
39
votes
3answers
16k views

Why can’t the genesis block coinbase be spent?

According to the bitcoin wiki: The first 50BTC block reward went to address 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa, though this reward can't be spent due to a quirk in the way that the genesis block is ...
28
votes
1answer
12k views

What is proof-of-stake?

As we know one of the important mechanisms of Bitcoin is proof-of-work. How does the concept of proof-of-stake work? How does it differ from proof-of-work?
26
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2answers
15k views

What does the term "Longest chain" mean?

What does the term "Longest chain" mean, as there is only one 'right' blockchain exists? How another longer chain would make the 'right' chain invalid?
23
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2answers
5k views

What are the pros and cons of Ripple's consensus as compared with Bitcoin's proof-of-work?

One of the major differences between Bitcoin and Ripple is how they process transactions. I can think of three ways in which Ripple's "consensus" scheme is superior to Bitcoin's proof-of-work: Less ...
20
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2answers
82k views

How does one mine Stellar

I was able to mine Ripple for a time using boinc, will Stellar offer something like this? are there other ways to mine Stellar?
18
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3answers
5k views

Are there alternatives for proof of work?

Bitcoin uses proof of work to secure the network, Ripple uses a global consensus system and PPCoin uses proof of stake. Are there any known alternatives to the above methods?
17
votes
1answer
1k views

What happens when a miner does not claim all fees/generated coins?

Suppose that a miner for some reason has the generation transaction of their blocks not take all the possible coins. This can happen for a variety of reasons, almost all of which are bugs: An off-by-...
12
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3answers
6k views

How can we trust supply won't be increased in 2140 by just a few lines of code?

How can we trust supply won't be increased by just a few lines of code?
12
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3answers
5k views

Byzantine fault-tolerant consensus - Why 33% threshold

Can somebody tell me why in dbft the threashold is 1/3 for malicious nodes? I mean that seems pretty abitrary. I have no problem if it is abitrary but is it? Note: I'm not referring to Bitcoin. I ...
12
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2answers
2k views

Bitcoin without mining

Several months ago I've stumbled an interesting question about the Ripple system: How does Ripple solve the double-spend problem? Specifically about how double-spending is solved in Ripple. As you ...
11
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2answers
6k views

Bitcoin without mining - what needs to be implemented

I have read this related question - Bitcoin without mining and I am trying to understand the very basics of Bitcoin network and the blockchain. I wonder, if we take the mining out of Bitcoin, what ...
11
votes
3answers
1k views

Do "the official bitcoin developers" control Bitcoin?

Is there one person or organization that controls Bitcoin? What if Gavin Andresen, the lead developer, or Bitcoin Foundation, "the official bitcoin organization", decide to change something? What if ...
11
votes
1answer
467 views

Did the introduction of VerifyScript cause a backwards incompatible change to consensus?

My question is about the changes to bitcoin done by commit range [a75560d8, 6ff5f718], and their effect on consensus. Out of this range of four commits (all attributed to satoshi) during the dates ...
11
votes
1answer
634 views

How does Ethereum achieve consensus?

It appears that Ethereum will start out with PoW and switch to PoS later. If I remember correctly, the block interval is planned to be fairly short in Ethereum. How does Ethereum manage to achieve ...
9
votes
3answers
904 views

How is Bitcoin governed by mathematics?

I keep hearing talks from Bitcoin evangelists that claim Bitcoin isn't governed by any central authority, rather it's governed by mathematics. What exactly do they mean when they say "governed by ...
9
votes
3answers
6k views

How does Proof of Burn work?

I have been trying to make a comparison between PoW, PoS and Proof of Burn. While I understood the other two, I want to know how exactly Proof of Burn helps in attaining the consensus. One burns ...
9
votes
2answers
3k views

Is there a maximum size of a scriptSig/scriptPubKey?

Previous research: Transaction's maximum size What is the maximum size of a transaction? The maximum size of a standard transaction is 100k bytes. Are there any consensus rules that prohibit ...
9
votes
2answers
1k views

Why are banks and other centralized entities interested in block chains?

Apparently banks and other centrialized entities are interested in block chain technology. My question is, why? The whole point of block chains is for decentralized, trustless, consensus. Bitcoin, ...
8
votes
2answers
2k views

How do Bitcoin devs make sure that their modifications do not affect the consensus rules or the running network protocol?

I understand that Bitcoin consensus rules are enforced by every single node individually. However, most people run the default version of Bitcoin Core, which makes the implementations done by Bitcoin ...
7
votes
2answers
597 views

How does the BTC protocol guarantee that a "main" blockchain emerges?

I'm reading up on the bitcoin/blockchain technology. Usually, the part about proof of work and how to create a block is well explained. However, what is never explained is how/why the communication of ...
7
votes
4answers
1k views

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? I think it's mathematically proven that in a distributed system,...
7
votes
1answer
1k views

What is the exact consensus protocol Ripple uses? [closed]

Ripple supposedly incorporates transactions into the ledger using a consensus protocol. I have been looking everywhere for a clear, formal, and precise specification of the protocol and could not find ...
7
votes
1answer
152 views

CVE-2012-2459 , possible code and performance improvement, is my logic correct?

ok so, in my effort to create a fullnode from scratch both for learning purpose and need (not a topic for discussion, thanks), I was looking at the code that check Merkle Root to not be vulnerable to ...
6
votes
4answers
1k views

What is the problem that mining solves?

Of course, the function of mining is to secure the blockchain, but I'm looking for a more abstract summary of what the exact problem is that mining tries to solve? I believe its called the Byzantine ...
6
votes
2answers
520 views

What does 'signal' and 'lock-in' mean in a BIP?

I have a vague idea about the jargon used over there, but what exactly do 'signal' and 'lock-in' mean specifically?
6
votes
1answer
5k views

How does a new block get distributed

I understand how a new block gets created, and verified by the miner that created it. But then, does it advertise this new block to near nodes? And how do these nodes go about verifying this? Do they ...
6
votes
2answers
380 views

What is the reason for using PoW in bitcoin?

As we know bitcoin uses Proof of Work Concept and it introduces never ending long block chain and some other issues. Why is it not designed in a way to use consensus algorithms what ripple uses? What ...
6
votes
1answer
698 views

Why does Ripple's consensus process have a 80% threshold?

A transaction is confirmed if 80% of the nodes in the UNL accept it. Where does this 80% number come from? Could it just as well have been 79% or 81%? What about 51%? Can different nodes have ...
6
votes
2answers
401 views

How does Ripple solve the sock-puppet problem during consensus?

I'm under the impression that Ripple uses a consensus based system in order to determine which of two payments is the authoritative one, with the other getting rejected due to a lack of proponents. ...
6
votes
1answer
390 views

Why bother having limitations on Bitcoin Coinbase Transaction Scriptsigs?

There are a few limitations on the structure of the coinbase (reward) transaction in a block. There is only one input. vin.size() == 1 (source) It doesn't reference any previous output. vin[0]....
6
votes
1answer
189 views

What happens in an extreme case if Ripple fails to make a consensus? Will that part of the network be segmented off?

What if the Ripple trust network becomes many trust hubs and spokes, and the hubs don't trust each other? In this extreme case, that could exist due to extreme network segregation, massive trust-...
5
votes
4answers
2k views

Would Bitcoin still work without a target difficulty?

Suppose that Bitcoin nodes had no target difficulty at all, and instead just accepted the block with the largest PoW every 10 minutes. Ignoring the increased bandwidth (since nodes would be ...
5
votes
2answers
2k views

How is a blockchain split resolved?

Let's say two miners created 2 different blocks and broadcast them into the network. Now some clients see blockchain 1 and other blockchain 2 which are different from each other. I would like to ...
5
votes
4answers
602 views

Why can malicious miners not award themselves with any number of bitcoins?

Why can malicious miners not award themselves any number of bitcoins? Is that because the award itself is a transaction which has to be confirmed by a random miner? And if so, what if the miner ...
5
votes
2answers
328 views

Why didn't Bitcoin implement segwit in the first place?

Why didn't Bitcoin implement segwit in the first place? Why and how does non-segwit Bitcoin enable a miner to change a transaction's txid? From Mastering Bitcoin ch. 7 § "Transaction identifiers": ...
5
votes
3answers
247 views

Has PoS really been proven secure under comparable assumptions as Bitcoin?

I am just reading this paper which claims to be a formal proof that Cardano's latest Ouroboros PoS protocol ("Genesis") gives similar security guarantees than Bitcoin's PoW protocol. Unfortunately, it ...
5
votes
1answer
329 views

In what sense does the security model of proof-of-stake require users to "log on to the internet every few months"

This is primarily a question about something I heard Vitalik Buterin say in an interview the other day. (Unchained podcast's January 9, 2018 episode, at 34 minutes, 15 seconds) I quote: As far as ...
5
votes
2answers
637 views

How do transaction fees exacerbate instability in Bitcoin in the future?

I came across the paper On the Instability of Bitcoin Without the Block Reward where it says that in the near future where the incentives are only due to the transactions, instability issues will ...
5
votes
2answers
427 views

Is Bitcoin a decentralized time-stamping authority?

Can Bitcoin/blockchain be thought of as a decentralized time-stamping authority (TSA)? Is there true consensus in the Bitcoin network on a mined block's time, or just that the block was mined?
4
votes
4answers
3k views

where is difficulty target inserted?

All miners at any time must have a consensus on the "difficulty target" to be able to achieve the correct nonce (as answer of proof-of-work). Assume that the target has been updated (it means that ...
4
votes
1answer
497 views

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

According to this answer: https://bitcoin.stackexchange.com/a/58908/41513 a Byzantine Fault Tolerant (BFT) consensus threshold is 1/3. On the other hand, there is a common belief that Bitcoin network ...
4
votes
2answers
242 views

what if the timelock is in the past?

I just started learning about bitcoin scripting and wonder: what if the timelock in CLTV is in the past? what if the timelock in nLocktime is equal to 500.000?
4
votes
1answer
459 views

Who decides the block reward in Bitcoin?

I know that when a miner mines a block, he will be rewarded with some bitcoins. But who decides how much bitcoin he will get? If it is decided by all the miners (as they are the ones verifying ...
4
votes
1answer
281 views

Why was BIP34 (Block v2, Height in Coinbase) not implemented via the coinbase tx's locktime or nSequence?

At some point in 2011/12 miners started using custom mining algorithms ignoring the best practise to mine to a different new public key (hash) for each subsequent block. This lead to a lack of ...
4
votes
3answers
882 views

How does a miner get selected in Proof Of Stake?

I am trying to understand POS. I get that POS uses currency held analogous to the hash power held in POW system. More the stake we have, more are our chances of mining the block. At various sources I ...
4
votes
1answer
2k views

List of Bitcoin consensus rules?

Is there a comprehensive list of Bitcoin's core consensus rules anywhere? In the Bitcoinwiki "Full Node" article it says: Here are examples of consensus rules, though there are many more: ...
4
votes
1answer
893 views

IOTA Security with Tangle

I don't know if this is the best place to ask this, but I've been reading about an interesting cryptocurrency called IOTA which doesn't use a blockchain exactly but instead uses a directed acyclic ...
4
votes
1answer
210 views

How does Bitcoin avoid splitting into multiple p2p networks?

So since Bitcoin is completely decentralized what stops multiple p2p networks from being formed? And what happens with the block chain when two separate P2P networks eventually reach each other? Will ...
4
votes
1answer
986 views

Ripple Distributed Consensus Algorithm

What kind of a Consensus Algorithms does ripple use? Is that a leader or leaderless distributed consensus algorithm? Then what?

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