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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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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How to establish connection for mining testnet blocks?

I am new here. I really want to know how scryptcoins work so i wanted to create and altcoin to learn on something. I learned c++ years ago so i know i have some basic knowledge but sometimes i get ...
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Are there any works of science fiction out there that relate to blockchain technology?

It feels like science fiction is lagging behind Bitcoin and the blockchain technology that is powering it. Are there any writers who have discussed similar technology in their stories? Even in the ...
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(JAVA) Get address balance from the blockchain

I'm a merchant that is currently developing client that I will use for receiving transactions for my business. I would like my client to be able to check how much Bitcoin the address sending to me ...
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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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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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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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48 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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556 views

Uses of computing power by bitcoin miners

How much of what this article says is true? I thought I had read that bitcoin miners are the ones who maintain the blockchain. Do they also do something other than maintaining the blockchain? In ...
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Query Transaction data based on past transaction id?

The blockchain.info API allows for quering information about a particular Transaction by its ID. But if you want to follow the coins to the next transaction, I'm not seeing what the next query should ...
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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 ...
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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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New To Bitcoin…Please Help! Bitcoin not received from sender to Armory Wallet!

I am in desperate need of assistance! I am new to Bitcoin so please apologies for the lack of knowledge in these matters guys....We all have to start somewhere ;) I sent my Bitcoins from the ...
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“Watch only” wallet and a private key

i recently bought a BTC wallet from my friend, it has a cold storage wallet ("Watch only") and a private key (which is a bunch of numbers and letters) for Blockchain. How do I use it in Blockchain? ...
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157 views

Can the Bitcoin blockchain eliminate the need for Trusted Computing in Smart Contracts?

Let me preface this by saying that I'm a novice, but this is my rough understanding of how Bitcoin's blockchain works. (This is largely based on blog posts like this one.) If person A wants to ...
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56 views

Cannot allocate memory

EXCEPTION: 11DbException Db::get: Cannot allocate memory bitcoin in ProcessMessage() Downloaded 250k blocks, now it won't run anymore i'm running ubuntu 12.04, I have 20GB HD and 1gb ram. any way to ...
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137 views

Trust Less Database Design?

I'm a young developer and have been following the bitcoin community for some time now and have wanted to contribute to a project. Have not fully read through the bitcoin protocol, but from my ...
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32 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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229 views

Bitcoins Stuck?

This morning I attempted to send BTC to my Bter account from my Mt Gox account. I sent them and they seemed to reappear. I sent them again and there was a little left over, I sent that. Now the ...
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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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Possible to use BlockChain.info and Bitcoin-QT synced?

I've used both BlockChain.info and Bitcoin-QT. Is it possible to use the same addresses on both? I don't have a incredibly large amount of bitcoins, so I'm not worried about it getting hacked into, ...
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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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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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How much space does the blockchain take up per day and per hour when running bitcoinQT on my computer?

the blockchain is about 20GB today, but i was wondering how much space does it take up each day if i were to leave bitcoinqt on regularly? also by hour? reason why im asking is im thinking about just ...
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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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131 views

Blockchain API support - receive payment IPN

I'm having some real trouble setting up the Blockchain API on my server First off is it possible to test it offline with local host? Secondly, how do I set it up so when a tx is made through my ...
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Chronologically sorting transactions within a block

Is there any way to chronologically sort transactions within a block?
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Is there a database of all transactions?

The blockchain is a database of all valid transactions, but is there a company/project that also logs all transactions which were broadcasted, but didn't made it to the chain? Blockchain.info for ...
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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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If more than one coin did the “mini-blockchain” proposal, would that make the weaker coin vulnerable?

So, I was reading this paper as a proposal to the ever growing blockchain problem. In summary, it's security is provided without a full blockchain by having a proof chain with these fields: Previous ...
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366 views

Armory client shows transaction unconfirmed

I am new to btc and am using the Armory client. Yesterday I transferred some btc to wallet from my MtGox account. The wallet showed the btc received within minutes, but, after 12 hours it still shows ...
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What's the formula giving the % of succesfully maliciously messing the blockchain?

With the recent (early 2014) GHash.io concerns about that particular mining pool getting too big, many people have talk about what a powerful miner could do if it wanted to "harm" bitcoin or ...
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395 views

Details on Genesis Block

The question asked here displays the genesis block in pretty good detail. I am still trying to get a breakdown of some of the elements seen here (and some others not seen here): The Merkle Root Time ...
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228 views

How do I scan my bitcoin receipt into my wallet?

I bought Bitcoins from the Robocoin ATM (I'm told it's the only one) and it gave me a receipt with a QR code to scan into my wallet. I downloaded Blockchain, but don't see where in the app I can scan ...
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pending payment

Three days ago I sent a payment via my MultiBit wallet but it is still marked as unconfirmed, only 4 confirmations. How long it will take this transaction to become fully confirmed? Thanks.
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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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How to get current BTC rate for BRL(real) using php cURL or javascript

Is there anyway to get current rate of BRL = BTC. I saw the blockchiain ticker. But the value for BRL currency is not updated As listed here in preev. I want to get the current 1BTC= how much BRL ...
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293 views

“offline” blockchain querying library

Is there a library which provides all the same address/transaction querying information as blockchain.info, depending only on having a bitcoind synchronised database? There are a number of queries ...
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How did transaction malleability/DDOS attacks allow an exchange's internal accounting system to get “out of sync”?

This Coindesk article says that: “So as transactions are being created, malformed/parallel transactions are also being created so as to create a fog of confusion over the entire network, which ...
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Query unspent outputs for arbitrary address

Is there a way to query all unspent outputs for an arbitrary address (which I don't have the private key for), without resorting to a third party service (like Blockchain.info). bitcoind apparently ...
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78 views

How do I iterate through the entire Blockchain using RPC?

I'd like to iterate through the entire block chain using RPC. The process I intend to do is: getblockhash 1 getblock (input of #1 here) iterate through each transaction with GetRawtransaction ...
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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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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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>50% crash induced by stakeholders of current financial systems

This is a though I had a few days ago. There are stakeholders of our current financial systems who would like to secure their wealth. If these stakeholders sense bitcoin as a threat to their wealth, ...
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Location of blockchain locally on different platforms, and structure of blockchain file?

I just downloaded Bitcoin-QT, and torrented a snapshot of the block chain that is a couple weeks old. I put the bootstrap.dat in ~/Library/Application Support/Bitcoin and started up the app. Right now ...
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Listening for changes to my own wallet in the blockchain

I would like to be notified of changes to any of my many wallet address as soon as they happen and then programmatically take action. I have been using wallet notify but this has been giving me really ...
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256 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 ...
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46 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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320 views

Bitcoin-qt falls behind on blockchain, how to replace?

On Apple Mac, bitcoin-qt is 14 days behind. Never approaches current time. Have downloaded current blockchain from trusted source. Where to install? What procedure?
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209 views

How to calculate bitcoin days destroyed percentage

I understand the concept of bitcoin days destroyed but on the wiki https://en.bitcoin.it/wiki/Bitcoin_Days_Destroyed And the site calculating it http://abe.bitcoinstats.org:2750/ They give a ...