The blockchain is a list of all transactions that have occurred using the Bitcoin currency. Please don't use this tag for the service named 'blockchain.info'.

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Where to place Bitcoin bootstrap.dat

I'm sure this has been asked many times before, but I've recently gotten into the whole cryptocurrency thing starting with Dogecoin, and I now want to use Bitcoin as well. I am on Windows 7. I found ...
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5answers
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How do you create a planet-specific cryptocurrency that will ignore longer block chains from other planets?

I'm sure that cryptocurrencies will play a huge part of the economy across the solar system, when we have colonized many different planets, moons, and asteroids. But there are problems with using a ...
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36 views

multiple parties to sign a transaction before being broadcast (or after, but either way be associated with)

Lets say someone was writing a transaction solely to denote the existence of something, or a timestamp, or writing something in OP_RETURN Could that transaction be signed by other addresses, kind of ...
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1answer
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How frequent are side-chain reorganizations of various lengths?

I'm wondering if anyone has collected statistics on how often reorganizations of side-chains with length 1 happen in comparison with lengths of 2, 3, or more. Related: What is the longest chain ...
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On quering the blockchain, can someone read what transaction took place? [closed]

Like considering the Alice Bob ex where Alice is the customer and Bob is the merchant. If Alice and Bob signed a contract where alice will pay bob on the delivery of a service. The transaction took ...
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1answer
89 views

Blockchain growth projections and risks

What is the projected block chain growth over time and could an attack on Bitcoin be lauched that creating an enourmous number of micro-transations to fracture the currency (e.g. spamming the system ...
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2answers
137 views

Block nonce predictable

Is the block nonce predictable in any way? It seems to be a proof of work on his own just like the block hash, but may a miner force a mined block to have a specific nonce? (if his hashrate allows him ...
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1answer
44 views

Include checksum in a transaction

Is it possible to include a file's checksum in a transaction? Not necessarily in Bitcoin's current blockchain due to the now limited OP_RETURN feature, but just in the blockchain/transaction concept ...
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1answer
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How does NXT prevent blockchain bloat since it does so many different things with its blockchain?

How does NXT prevent blockchain bloat since it has a built in message system and other features? Wouldn't the NXT blockchain grow to be really big in the future and pose a problem for people storing ...
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Why does Bitcoin store all transaction inputs and outputs, instead of just an “account/balance” ledger?

From what I can tell, the Ethereum blockchain just stores accounts and balances - why did the original Bitcoin developers choose the method of storing all transactions for validation instead of just ...
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Blockchain Pairing API

Have anyone of you figured out how can we use devices pairing in 3rd party applications? I've found that pairing QRCode looks like this: "1|<blockchain_login>|<some_hash>", where ...
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1answer
268 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, ...
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1answer
65 views

Is it possible that someone forks the chain?

I'm not sure I understood everything but all the clients always keep the longest chain, ok. So, what happen if an evil person inject bad transactions in a block and successfully mine it (given the ...
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Confirmation limit

When seeing transactions I see that the number of confirmations keeps increasing without any limit. I wanted to know if there is any time limit on including a already confirmed transaction in a block ...
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3answers
243 views

How To Lower The Disk Space Needed For Full Blockchain?

I'm looking to run bitcoind on a virtual machine. However the main nets Blockchain size is over 21GB, and growing. Is there a way to compress this down or lower the amount of disk-space needed for ...
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1answer
44 views

Blockchain and Bitcoin client difference of amount

I just made a transfer of 0.06 BTC, you can look it up on Blockchain.info The problem now is that my receiving client (Multibit) doesn't show those 0.06 BTC, it only shows 0.0001 BTC have been spend ...
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1answer
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Can you assume that all inputs to a Bitcoin transaction are controlled by the same person?

When you are looking at a Bicoin transaction in the block chain and it has inputs from multiple addresses is it safe to assume that those addresses are all controlled by the same ...
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1answer
116 views

What percentage of Bitcoins stored in a multi sign address?

I am looking for a statistic of the usage of multi-sig addresses over time. More concrete: what is the percentage of Bitcoins stored in a multi-sig address over time.
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145 views

What is current size of various databases in Bitcoin Core as of July 2014?

This question is related to question: What is the database for? What is size in MB of: blockchain itsef - blocks/blk*.dat blocks/index/* chainstate/* blocks/rev*.dat Is the size of chainstate and ...
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2answers
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Are NXT messages stored on the blockchain and are they encrypted or publicly viewable?

Are nxt messages stored on the blockchain? What is the character limit on these messages? And are the messages encrypted or publically viewable? If they are public, is there a site to just view all ...
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1answer
115 views

getrawtransaction doesn't work for every transaction with -txindex=1?

i put txindex=1 in bitcoin config and reindex blockchain after that when i call getrawtransaction for some transactions didn't exist in my wallet and work well like: [Working] getrawtransaction ...
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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 ...
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1answer
262 views

How big is the NXT blockchain in disk usage compared to the Bitcoin Blockchain as of June 2014? And rate of increase?

Currently I'm looking for the disk usage size of the NXT and Bitcoin blockchain size as of June 2014 and the current rate of of increase every day/week/year?
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56 views

What determines how many transactions end up in a given block?

What determines how many transactions end up in a given block? Blocks can have various numbers of transactions, so what decides how many are in a certain block?
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How do I prevent Bitcoin-qt from having to keep reindexing the blockchain?

Is it likely that anti-malware or anti-virus software is causing this issue? (I have told such programs to exclude the Bitcoin folders from scans)
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1answer
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What is the best way to implement withdrawal in online service?

Suppose we have a service, which holds user balance in Bitcoin. How to implement withdrawal from bitcoin perspective? Which RPC call to use? How to archive transaction to have a proof of sending ...
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blockchain - strange problem

I have Windows 7 and i’m using the bitcoin-qt client v0.8.6-beta. Last night i tried to open up the client – but there was a message that said i had some issues with the blockchain. Which is weird, i ...
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Custom altcoin won't sync with node and neither will accept a miner connection

I forked the BlackCoin source, changed the ports, generated the genesis block, merkle, blah blah blah. I set up a node on a DigitalOcean server and compiled my coin daemon there as well as on my local ...
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1answer
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Created genesis block and set up node. How to mine?

Everything seems to be going well creating my altcoin for fun. I forked the BlackCoin source on Ubuntu, successfully mined a genesis block, recompiled. I bought a droplet over on digitalocean running ...
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1answer
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Why is my new altcoin trying to connect to peers and sees almost 200k blocks remaining?

I downloaded and forked the Blackcoin source code. I changed all of the references to BlackCoin, changed the pszTimestamp string along with the current Unix timestamp. Then, I successfully mined the ...
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1answer
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Miners produced/ing duplicated hash values

This transaction is contained in two MainChain-Blocks: https://blockchain.info/tx/e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468 On Blockexplorer there is a note of this anomaly: ...
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1answer
363 views

what is Create wallet using blockchain api (PHP)

Im wondering to know, what is use of Create wallet programitically Block chain API Block Chain api here What it will provide? Where can i get the api code? Any tutorials ? Can i provide my ...
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1answer
58 views

How to find a block containing a transaction using transaction hash only?

Well, the title says it all. I have a transaction hash and I want to find this transaction in the blockchain. I am working with bitcoinj. I am probably missing something very obvious here, but I ...
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1answer
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Purpose of a BlockChain in local wallet application

I have installed the BitCoin wallet application on my PC, so that I can cold store my BitCoin. It's "Synchronizing with the network" and has 272 weeks of BC left to download (painfully slow!!) What I ...
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1answer
798 views

How many coins does Satoshi have? [duplicate]

There are rumors that the creator of Bitcoin, Satoshi Nakamoto, currently possess as much as 1.5m bitcoins. What are the steps involved to determine / guess how many coins Satoshi has?
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1answer
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How to choose address in BlockChain Android Application?

If I want to receive funds using the Blockchain Android application I click on the arrow on the top of the screen which brings up the Request Bitcoin screen, showing the QR-code for easy scanning. ...
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How to find utxo?

I might be over thinking this, but I'm trying to figure out the best way to build an unspent output pool. Should I just naively parse every block? Every input gets removed from the hash set, and every ...
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2answers
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Is there database of orphaned blocks?

Is there database of orphaned blocks? https://blockchain.info/orphaned-blocks does not work right now Does anybody keep them? Also I am looking for those transactions which were not included in ...
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1answer
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How can “undo” bitcoin transactions be “private”?

BitUndo private transactions: If you choose to make your undo transaction private, nobody will be able to see that you tried to undo a transaction, unless it succeed. You have to know that a ...
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1answer
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Wallet programming, search transactions by address

This may be a silly question, but I keep running in circles. Using either bitcoind or JSON-RPC is there a way to search all transactions involving a address hash? I understand every wallet and most ...
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How do we check the time when a transaction hits x confirmations?

Consider the transaction 948a427.. which has 3341 confirmations as of now: We can see that the time the relay is received at 8:36:30 and it has one confirmation at 08:50:04 (after 14 minutes). How ...
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1answer
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A clarification about Wallet and Addresses (In Armory)

I've just a dumb (Probably) question about bitcoin wallet and addresses (in Armory): If I've understood correctly (Correct me If I'm wrong), a wallet works as a "container" where you can store ...
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1answer
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Optimising the inputs for a transaction

I have a list of unspent outputs. Let's say: 0.4 BTC, 0.6 BTC and 1.0 BTC. Now I want to create a new transaction for a 0.5 BTC. How I understand it, it would be best to take the 0.6 BTC output as ...
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How does a Bitcoin client know its transaction has been accepted by the whole network?

Say Belly, Alice and Teddy are Bitcoin clients. Belly makes a transaction to send 1 btc to Alice. He broadcasts this transaction to the P2P network. Teddy calculates a valid hashcode and add Belly's ...
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1answer
238 views

How can Blockchain.info wallet send unconfirmed bitcoins?

So i just opened a Blockchain.info wallet after years of using Bitcoin-qt. My Blockchain.info wallet had an empty wallet, i sent some bitcoins to it and right after that without waiting for ...
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1answer
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How will the new Internet Neutrality Act affect Bitcoin?

How do you think the neutrality act that is being talked about as I write this post will affect the Bitcoin community. Not only in transactions, but mining, how will it affect Bitcoin economically ...
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1answer
88 views

Why doesn't the Bitcoin blockchain truncate past data? [duplicate]

AFAIK, verification of transactions on the blockchain doesn't require the full chain data and six to ten verification will be enough (which makes uses of a Merkle tree). Thus, why cannot it abridge ...
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2answers
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SHA256 * 2 on header - what am I doing wrong?

I've been experimenting with the php code here: https://en.bitcoin.it/wiki/Block_hashing_algorithm (after correcting the small bug of $x=; to $x=""; ) With these blocks 0 and 125552 (for example) it ...
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2answers
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How Is Block Assembled?

I think I understand mining well enough, but what I don't get is how the blocks of transactions are assembled. According to this post - What exactly is Mining? - the miners assemble the blocks and ...
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1answer
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Transaction verification up to coinbase?

Do full nodes verify the entire transaction chain up to coinbase when verifiying a single transaction to be included on the block which they are working on ?