Questions tagged [blockchain]

This tag should be used for questions pertaining to the blockchain. The blockchain is a list of all transactions that have occurred using the Bitcoin currency. It consists of blocks which are linked to each other, and each block consists of transactions. DON'T USE THIS FOR THE SERVICE NAMED 'blockchain.info'!

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10
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2answers
1k views

Does block validation get more difficult as the blockchain grows?

I just downloaded Bitcoin 0.5 and started downloading the blockchain from scratch. The process was rather fast early on but slowed down noticeably later. That could of course be related to network ...
7
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1answer
205 views

Is the time a transaction was done recorded in the block chain?

Is there something like a timestamp of each transaction recorded in the block chain, or only the mere fact that the transaction was done?
4
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3answers
1k views

Limit size of data files

As the mere size of the constantly changing data file tampers with my backup concept, I would like to ask if there is a way to split this file into many smaller pieces. I have no problem with the size ...
25
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2answers
8k views

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 ...
8
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1answer
1k views

Where can I see the average transaction fee payed in the last 100 blocks?

Is there a site that shows what's the average transaction fee payed in the last X blocks? Or just raw data about this? I checked BlockExplorer and Sytes and they don't seem to show this information.
9
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1answer
227 views

One dataset for many wallets… how?

It takes a while to download and process the transaction log. Doing that for dozens of wallets would be a big waste. I want to run just one client full time as a log processor. Then for each wallet, ...
15
votes
1answer
1k views

How can a non-miner store data in the block?

If I am not a miner and would like to put arbitrary data in the block chain, is there currently any method or protocol to get a miner to add it for me?
8
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2answers
2k views

Are private keys published to the blockchain after spending coins from a wallet?

Always I spend coins the final balance of the address that is used for transaction will go to zero. The remaining coins comes back as a change to a new address. Will this indicate that the private key ...
38
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3answers
10k views

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? ...
29
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5answers
3k 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 ...
8
votes
2answers
768 views

Why isn't there a fast blockchain update inside a LAN behind a router between two Bitcoin clients?

This is the scenario: 2 computers on a LAN with private IPs (192.168.X.X) router forwards port 8333 only to one of them (the 2nd one). one computer has the full blockchain updated in its Bitcoin ...
45
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8answers
101k 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 ...
7
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3answers
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Largest number of bitcoins at a single address at one time?

What is the largest number of bitcoins that were stored in a single address at any one time to date? I know there were >474320 BTC at this address at 2011-07-18 (identified to be MtGox's from the 424 ...
11
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1answer
769 views

Is there a limit to how much extra data can be put into blocks via scripts?

According to this answer, miners can include extra data in blocks. Is there an upper bound to how much a miner can add? How much?
4
votes
1answer
531 views

When will the official client support partial blockchain downloads?

Are there concrete plans for the official client to be able to download just a portion of the blockchain? By concrete I mean what's the issue tracking this on github, is there a planned version for ...
9
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2answers
1k views

Does encoding Namecoin/messages into the blockchain bloat it?

I read today twice concerns about inflating the blockchain: NameCoin Bitcoin Message Service So, does using these services "over inflate" the blockchain? The way I see it, if another protocl rides ...
12
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3answers
3k views

What will happen when SHA 256 needs to be replaced?

MD5 used to be the hash algorithm. Everyone loved it, but now, not so much. What will happen to bitcoin if flaws are found in SHA256 in the future?
10
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1answer
701 views

Strange transaction (block 71036)

What happened to this transaction? Can someone explain it? http://blockexplorer.com/t/9eHTFRi3Qq
13
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2answers
628 views

What was the most recent change to the official client that broke block validity?

There have been suggestions that various bitcoin protocol rules (max block size, mining reward policy, etc) could be changed in the future by everybody "agreeing to update their client". The ...
4
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1answer
523 views

Raw block / other messages

Where can I find a raw version of the Bitcoin blocks and other messages that are sent between the Bitcoin clients?
2
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1answer
806 views

How do the clients agree on the target to hash for? [closed]

Edit: They do not agree on a specific target hash. Any hash lower than or equal to the difficulty is sufficient. This means clients only have to agree on difficulty.
6
votes
4answers
276 views

Can new types of transactions be included the current block chain?

I was putting an answer for this question together when I realised my idea would require a new type of transaction to be invented and included in blocks. Then I wondered how that could work. There ...
5
votes
1answer
685 views

How are transactions in discarded forks merged back into the blockchain?

It sounds like transactions in discarded blocks are propagated back to the network to be included in the next block to be generated, is that the case? If so, is that triggered in the client when it ...
21
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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?
14
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3answers
1k views

Bitcoin usage charts

There is a lot of data out there about BTC prices, but are there any simple charts which show how much is Bitcoin really used? Something like number of Bitcoin transactions per day/week, or daily ...
27
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9answers
5k views

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 // ~...
44
votes
1answer
8k views

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 ...
5
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2answers
417 views

What incentive is there for a miner to not include a bad transaction?

'A' has got 1BTC legitimately. He sends out a transaction to transfer that one bitcoin to 'B' with a 1BTC transaction fee added on. (i.e. a bad request.) 'C' is a miner who cares nothing for ...
75
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7answers
77k views

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 ...
9
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2answers
448 views

What prevents bitcoin from breaking down in case of a “transaction attack”

Let's say that I want to kill Bitcoin by means of a transaction attack. What in the bitcoin system prevents the following approach: I buy a limited number of bitcoin in the market. Using a small ...
18
votes
1answer
3k views

Is the timestamp in the genesis block relevant?

Bitcoin's genesis block contains this text published in The Times on January 3rd, 2009: The Times 03/Jan/2009 Chancellor on brink of second bailout for banks According to the Bitcoin Wiki, this ...
5
votes
1answer
1k views

Why does the Bitcoin client require at least one confirmation before I can spend?

If I accept bitcoin for payment, provide a new address for each payment and make it clear to payers that I consider payment complete only after waiting the ~10 minutes for a confirmation, is there a ...
19
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3answers
1k views

How would the Bitcoin protocol be impacted if nodes only stored the blocks they cared about?

Right now, full clients of the Bitcoin network store every block ever generated (while "thin" clients instead rely on a node which does so). This greatly increases first-time initialisation for the ...
26
votes
2answers
9k views

When and how did Bitcoin start?

Exactly when was the first block mined and the first bitcoins generated? How many people knew about the project at this point? Had the project been publicly announced before the first block was mined ...
8
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3answers
379 views

How can you find out what is the latest block number?

When running a fresh client, or after not being connected for a while, the client takes some time downloading new blocks. How can you find out what is the target block number (the id of the newest ...
10
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4answers
2k views

Decentralized escrow functionality built into Bitcoin?

AFAIK there are a few websites out there that offer escrow services for Bitcoin. Those however are central, i.e. I have to "trust" them. Is it being discussed, is it theoretically possible, or does ...
36
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6answers
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.
15
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2answers
3k views

How can I view the current blockchain size?

How can I view the current size, preferably in bytes, of the blockchain? Is there a CLI command for bitcoind? Or a website that displays the size?
43
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4answers
62k 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?
9
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2answers
1k views

Is there an easy way to search all the transactions?

Is than an easy way to search the list of all bitcoin transactions? For example to find all the bitcoins sent to or from an address?
19
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4answers
5k views

What is the “blockchain”?

What is the blockchain? I keep hearing about other "blockchain technologies", does this mean other cryptocurrencies or what?
3
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0answers
327 views

Are there really messages in the blockchain? [duplicate]

Possible Duplicate: How can one embed custom data in block headers? Someone told me a hacker put messages in the blockchain. What does this mean? Edit: related asked/answered question How can ...
37
votes
10answers
26k views

How is it possible to launder bitcoins?

Some services, such as bitcoinlaundry.com, claim that they can launder your bitcoins. Since all bitcoin transactions are publicly logged, how is this done? Wouldn't it be possible to trace back the ...
10
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4answers
3k views

Is there a way to use the block chain as entropy in random number generator? [closed]

I want to create a transparent gambling/lotto site and use the block chain as entropy for lotto numbers, dice rolls, that kind of thing. Would the transaction hash of the latest transaction be the ...
63
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9answers
34k views

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 ...

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