Questions tagged [blockchain]

The journal of all confirmed Bitcoin transactions. The blockchain consists of a linked sequence of blocks and each block contains a list of transactions.—Please use [blockchain.info] for the eponymous UK-based company.

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Can someone explain how the Bitcoin Blockchain works?

I'm trying to figure out how the blockchain works and how to read it via blockchain.info website. Is there a laymen way of explaining how the block chain works and how to read the blockchain to trace ...
Patoshi パトシ's user avatar
51 votes
3 answers
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How can I run bitcoind in pruning mode?

I read this comment: You could consider running a pruning node, which is practically the same as a full node (including security), except it throws away some of the old history. Version 0.11 ...
user's user avatar
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41 votes
4 answers
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What are the keys used in the blockchain levelDB (ie what are the key:value pairs)?

I am wondering if I can use node.js and levelup to access a copy of the blockchain database directly. But from what I can see, I need to know the name of the key(s) before I can get any data, as this ...
T9b's user avatar
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66 votes
9 answers
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How anonymous are Bitcoin transactions?

I read some sources that say Bitcoin transactions are anonymous, some that say they are semi-anonymous, and some that say they are not anonymous at all. In what ways are the transactions anonymous ...
Michael McGowan's user avatar
62 votes
6 answers
68k views

What is the Merkle root?

The Bitcoin wiki Vocabulary article explains why the Merkle root exists: Every transaction has a hash associated with it. In a block, all of the transaction hashes in the block are themselves ...
Steven Roose's user avatar
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32 votes
9 answers
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Why don't the timestamps in the block chain always increase?

The timestamps starting at block 145044 are: 145044: 2011-09-12 15:46:39 145045: 2011-09-12 16:05:07 145046: 2011-09-12 16:00:05 // ~5 minutes before prior block 145047: 2011-09-12 15:53:36 // ~...
Mocky's user avatar
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29 votes
2 answers
6k views

Are there any studies into the size of the blockchain scaling over time?

After watching some of one of the 28c3 talks, It got me thinking about just how scalable Bitcoin really is. With the size of the blockchain currently, given the number of transactions/users, will the ...
Sean Chapman's user avatar
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80 votes
7 answers
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Can I download the whole block chain from somewhere?

Every time I turn on the Bitcoin client it takes days to catch up with the block chain. Are there alternatives to getting it trickling through the peer-to-peer network? Can I just download it ...
Thilo's user avatar
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33 votes
1 answer
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What is the database for?

I see the block chain is stored according to the block chain format specification. But I also see there is a database, which is currently a leveldb database. Why is the block chain stored in two ...
turtlepower's user avatar
6 votes
4 answers
13k views

What can I do when the blockchain synchronization is stuck at a specific block?

I hadn't started/used my Bitcoin client for ages. Now, whenever I start the client, it is downloading block 135407 and does not progress past it. What can I do?
Patrick's user avatar
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35 votes
3 answers
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What is the block maturation time?

I was reading the wiki article about the blockchain and I didn't understand the part in bold: When a block becomes an orphan block, all of its valid transactions are re-added to the pool of ...
nmat's user avatar
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12 votes
1 answer
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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, ...
morsecoder's user avatar
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39 votes
4 answers
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What are checkpoints?

I often read that checkpoints protect the network from a 51% attack because an attacker cannot reverse transactions made before the last checkpoint. How exactly does this checkpoint mechanism work? ...
nmat's user avatar
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10 votes
2 answers
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Will the proof-of-work system end when all bitcoins have been mined?

This article from ArsTechnica is claiming that Bitcoin is not such an environmental disaster, and one of the reasons they mention is that mining will come to an end. Ok, fair enough, there is an end ...
knocte's user avatar
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23 votes
2 answers
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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?
kermit's user avatar
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27 votes
4 answers
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What is a double spend?

What is a double spend? As someone who uses Bitcoin, what do I need to know about how the Bitcoin system prevents double spends? Are there still circumstances where they can occur?
Dr.Haribo's user avatar
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25 votes
1 answer
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How does Bitcoin read from/write to LevelDB

I know that Bitcoin Core uses LevelDB since 0.8 version. However, I couldn't find detailed explanation about how Bitcoin stores and retrieves from LevelDB. E.g. If B transaction uses an output from ...
Yangrui's user avatar
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15 votes
6 answers
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Creating my own bootstrap.dat?

Since I have been tearing down and setting up bitcoin clients a lot for some experiments lately, I was wondering whether there is a simple way to speed up the synchronization with the network. One ...
cdecker's user avatar
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0 votes
1 answer
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Reg: Watch only Address

I have been given " Watch only Address" by one of my friends. To make the funds credited into my account or to use the BTC, what is way to get the private key? Do we need to pay anything to ...
Lakshmana's user avatar
31 votes
5 answers
4k views

What would happen if a portion of the Bitcoin network was separated from the rest of the network?

Yesterday I asked a question over at SuperUser, so that I could have my facts straight before asking this question. The scenario sets the basis for this question. Regarding bitcoin, what would ...
RLH's user avatar
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28 votes
2 answers
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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?
vi.su.'s user avatar
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25 votes
1 answer
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What is a hard fork?

When people talk about possible changes to how Bitcoin works they sometimes say a particular change would require a hard fork. What does that mean? Can a hard fork cause problems?
Dr.Haribo's user avatar
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2 votes
1 answer
436 views

How does solving a block work in relation to the first letter/number after the 0's?

I did a terrible job of explaining it in the title so I'll explain here. Say the target hash to solve for a block is 00004aef... etc. does that mean that you can't solve the block if you get 00005fad (...
L M 's user avatar
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44 votes
1 answer
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What do the different .dat files contain?

What data do different Bitcoin .dat files contain? How about the other files in the same folder? The wallet.dat file is somewhat documented and there are some ways to convert it to human-readable ...
ThePiachu's user avatar
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39 votes
11 answers
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How to check if the block chain is up to date using bitcoind or json-rpc?

I read the full api method list and did not seem to find one. I suppose there is no command specifically for that purpose, so what is the general way of doing this? I would consider checking the ...
Steven Roose's user avatar
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20 votes
3 answers
5k views

What is the "blockchain"?

What is the blockchain? I keep hearing about other "blockchain technologies", does this mean other cryptocurrencies or what?
lemonginger's user avatar
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8 votes
3 answers
2k views

At what point is a new wallet known by the Bitcoin network?

I was just showing a deterministic wallet to a friend who asked "At what point is the wallet known to the network?" and I could only guess by saying that it is known only when a transaction is ...
T9b's user avatar
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8 votes
2 answers
2k views

What is the size of different Bitcoin transaction types?

I found this interesting take on Bitcoin transaction type trends from 2015. As that article is from 2 years ago, I am wondering: a. Are there any newer transaction types? b. What is the average ...
Nona Shah's user avatar
  • 101
20 votes
3 answers
2k 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 ...
CQM's user avatar
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14 votes
3 answers
8k views

What is a step by step way to insert data in OP_RETURN?

I was following https://bitcointalk.org/index.php?topic=453086.0 for creating a message in OP_RETURN. I am able to decode my raw transaction, but on signrawtransaction it gives error: {"code":-22,"...
wizgot's user avatar
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13 votes
1 answer
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File format -- rev*.dat

Can anyone help me to find out the format of rev*.dat file? There is an array with [F9BEB4D9 + 32byte number + variable raw data] for each element. What is that 32b number? And may be how to ...
Denis Leonov's user avatar
12 votes
2 answers
4k views

How can I read information from the blockchain?

I don't want to use an existing service, like Blockchain.info or BlockExplorer.com. Is there some library out there that will let me read the blockchain programatically?
Shamoon's user avatar
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0 votes
2 answers
208 views

Is it true that all the bitcoins in existence are on the blockchain (the ledge), but it just depends on who the owner (address) is?

It seems that for the 18.5 million bitcoins generated, plus even the 6.25 bitcoins that were rewards just 10 minutes ago, are all recorded in the blockchain (the ledger), but it just depends on who ...
nonopolarity's user avatar
0 votes
1 answer
806 views

How to differentiate between BTC transactions and BRC20 transactions on a blockchain?

How to differentiate between BTC transactions and BRC20 transactions on a blockchain using the RCP interface? This is a transaction record that contains BRC20 tokens which I found on a blockchain ...
Mashaji's user avatar
47 votes
8 answers
108k views

Where are the user's bitcoins actually stored?

On the person's computer? On bitcoin.org? :) Where does that information reside that tells others and me how much bitcoins I have? I assume it can't be on my PC because I could easily hack the file ...
Alex's user avatar
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45 votes
4 answers
86k views

How do I see the IP address of a bitcoin transaction?

How do I see the IP address that someone used to send or receive bitcoins with? Is it stored in the blockchain?
lemonginger's user avatar
  • 5,432
18 votes
4 answers
18k views

Why does each block store a Merkle root?

I understand how a Merkle root is calculated and stored in the block. But how do miners verify a transaction using the Merkle root? Here are 18 conditions that verify a transaction. None of them uses ...
Mohit Munjani's user avatar
12 votes
1 answer
14k views

How to transfer only the blockchain to a friend's computer?

After installing the bitcoin client (Qt) a friend got interested as well. He doesn't have as fast an internet connection, though, so I thought of burning some DVDs with the blockchains for him to have....
Joe Pineda's user avatar
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12 votes
0 answers
2k views

How can an earlier block have a later timestamp? [duplicate]

Block #180966 has a timestamp of 2012-05-20 23:02:53. Block #180967 has a timestamp of 2012-05-20 23:02:13. How has the software permitted a later block to have an earlier timestamp than its ...
Peter's user avatar
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10 votes
1 answer
30k views

Whats the process of Creating a Block on the BlockChain

have been mining on pools and blindly going a long for the ride of > generating a block Can somebody walk through the process in simple terms of the steps involved in creating a block on the ...
BitCoin New Guy's user avatar
8 votes
1 answer
5k views

Order of transactions within a block

Does the Bitcoin protocol guarantee that within a valid block, if transaction B spends the outputs of transaction A, A will always precede B? Or is it possible to have B before A?
Flavien's user avatar
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6 votes
2 answers
3k 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 ...
Haddar Macdasi's user avatar
6 votes
3 answers
15k views

Lost my Bitcoin wallet and have only 11 out of 12 mnemonic seed phrase words. How can I get my Bitcoins?

I am new to the whole Bitcoin thing, and I am having my first attempt almost going sour. I lost where I created my wallet. I have my Bitcoin address and only 11 of my mnemonic seed phrase words (of 12)...
Perry's user avatar
  • 111
5 votes
1 answer
1k views

What is a block?

I know bitcoin has a block chain that is from my best representation a list of blocks. I know the block holds many transactions. But i'm still very much lost as to what a block is and how a block can ...
Patrick W. McMahon's user avatar
3 votes
2 answers
2k views

Understanding how ordinals work with the Bitcoin blockchain. What is exactly stored on the blockchain?

Supposedly someone uploaded a Doom clone to the bitcoin blockchain: https://ordinals.com/content/521f8eccffa4c41a3a7728dd012ea5a4a02feed81f41159231251ecf1e5c79dai0 But I'm a bit confused on exactly ...
Patoshi パトシ's user avatar
36 votes
5 answers
36k views

How are transactions broadcast to the rest of the network?

If a person sends a transaction to another person, and Bitcoin is a peer-to-peer application, how will the transaction get to the rest of the Bitcoin community? How does everyone have the same ...
Patrick W. McMahon's user avatar
36 votes
6 answers
9k views

How do I reduce the size of the block chain data on my machine?

The block chain file is getting rather large, ~500MB. Is there a way to trim it or clean up, or maybe configure it to be limited in the future? I am using the stock Bitcoin client on Ubuntu.
browep's user avatar
  • 654
17 votes
2 answers
3k views

Is "Reclaiming Disk Space" already implemented? How effective will it be?

Some people are concerned about the scalability of Bitcoin. The blockchain already has reached nearly 1 GB to download and store, which is not exactly in the spirit of a modern thin client, especially ...
herzmeister's user avatar
  • 3,507
17 votes
1 answer
11k views

What happens when you send a transaction that ends up in an orphaned block. Is it recoverable?

I've found a lot of information regarding orphan blocks, but I can't find an answer to this simple question. If I send a payment to a user and my transaction happens to end up in an orphaned block, ...
RLH's user avatar
  • 2,172
15 votes
3 answers
5k views

Can Bitcoin-Qt be configured to trim the blockchain?

I run Bitcoin-Qt and Bitcoin Armory on a laptop. I don't have the space to store the whole 20 GB (or however big it is now) blockchain. I understand the need to run through the entire thing for ...
Sai's user avatar
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