Questions tagged [best-chain]

Discusses the rules by which one chain-tip gets chosen over another, including questions about heaviest/longest chains. Closely related to [chainwork], [chain-reorganization] and [blockchain-fork].

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45
votes
2answers
20k 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, ...
10
votes
1answer
4k views

Strongest vs Longest chain and orphaned blocks

Satoshi writes at the bottom of page 3 of his white paper that "If two nodes broadcast different versions of the next block simultaneously, some nodes may receive one or the other first. In that case, ...
21
votes
2answers
4k views

How does a client decide which is the longest block chain if there is a fork?

Is it only the block height or is it the effort that went into the forks? In other words: does this decision account for different difficulties?
25
votes
2answers
14k 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?
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 ...
8
votes
2answers
4k views

What is chainwork?

If I run the RPC call getBlock on the bitcoin-qt client it gives me field called chainwork containing a hash. I cant find any information what this value is about. Request: getblock ...
18
votes
3answers
1k views

Countrywide Internet isolation, inevitable fork

Many countries around the world have provisions for shutting off the Internet as well as isolating itself from the Internet (where networking within borders still flourishes), any transaction ...
8
votes
2answers
809 views

Can the blockchain be outpaced by a chain of low-difficulty blocks?

Let's say someone creates a blockchain fork starting from the genesis block, when the difficulty was absurdly low compared to today; then he starts mining new blocks from there up to the current block ...
6
votes
2answers
316 views

Why aren't block hashes used directly as scores for difficulty purposes?

Why does Bitcoin apply a difficulty function to block hashes and then use the output of this function to add up and determine the "longest" chain? Why not just e.g. add together all block hashes (as ...
3
votes
2answers
235 views

How do I know I can trust the head of the blockchain

I'm trying to understand how the mining process works. Specifically, my understanding is the local miner works on blocks and add them to their local blockchain if they succeed. It may turn out that ...
1
vote
2answers
190 views

How can Segwit increase transaction throughput if the same amount of data is stored in the blockchain?

I'm posting this after reading the answers to this: Where is the Signature stored in a SegWit transaction? I've found out from reading that, that in Segwit, the "witnesses" (or signatures) that ...
6
votes
2answers
2k views

What happens to extinct blockchains, and transactions inside of them?

While understanding the concept of block chain and proof of work, few things are confusing me. Miners always consider the longest chain(by difficulty) and work on expanding it. Now, lets say two ...
6
votes
1answer
210 views

How does Bitcoin Core know it's on the longest chain?

In trying to implement a client, I am wondering what is the most efficient approach to figure out if you are on a fork. Let's say you pick a peer at random and go through IBD using the headers-first ...
7
votes
2answers
6k views

What does “Activating Best Chain” mean?

What does "Activating Best Chain" mean? My Bitcoin Core doesn't freeze, it just takes a while. I'm curious as to what it's doing.
3
votes
1answer
180 views

Why Block Chain not Block Tree?

Why is the Blockchain intended to be a chain and not a tree? Why do orphaned blocks get trimmed off? Would you please provide a detailed answer.
2
votes
2answers
97 views

Can there be stale blocks in “header first” implementation?

The Bitcoin developer guide mentions stale blocks as not being in the longest chain, then moves on to orphan blocks. It states you don't get orphan blocks, "and if you do" they are just dropped. But ...
7
votes
2answers
570 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 ...
4
votes
1answer
253 views

When does a blockchain fork resolution happen?

I understand that forks are resolved by largest proof-of-work etc. but when do the miners decide to resolve a fork? Is it a question of network consensus or does each individual miner resolve at their ...
4
votes
1answer
151 views

How often does temporary fork occur and how long does it last?

I was wondering, how often does temporary forks occur? They appear when there are two different blocks mined based on the same previous block (parent block), but what are chances for that? And if fork ...
1
vote
2answers
261 views

Tie Breaker to reduce orphaned chains?

When two different miners find the same block number at roughly the same time, the chain is forked, and there is a bit of a race to develop a longer chain, leaving the alternative orphaned. Why is ...