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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How to fork an Altcoin Which has 0 Reward Block to continue mining after the LAST POW BLOCK

Im trying to learn how is it possible to Hard Fork an Altcoin Blockchain to Continue the Mining Phase after the LAST POW BLOCK. The Block Reward is already 0 and the LAST POW stops at Block 8000. And ...
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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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Double Spending - Does each node maintain a list of unspent transaction references?

My Understanding Of How Bitcoin Prevents Double Spending Each transaction contains references to the input transactions and ever node has to verify all transactions from time immemorial to ensure ...
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Querying insight-api to dump all addresses with a positive balance

It's been some time I've been using 'insight-api' (https://github.com/bitpay/insight-api) and I couldn't find any documentation / anything helpful to query leveldb in a way that all addresses with a ...
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1answer
6k views

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 ...
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How do I change the default blockchain Database download location for NXT?

I'm testing out the nxt client and was wondering how do i change the default database download location? Its currently downloading to the current folder (nxt_db).
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2answers
56 views

What methods are currently used to embed additional data into the Bitcoin blockchain?

Yes, I do understand that it is inappropriate to pollute the already large blockchain with data not necessary to make the currency work. But I know people are using Bitcoin as an underlying system for ...
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1answer
73 views

how to get one address from two public keys?

Parsing an input script of a transaction, I’ve come across two public keys in the script. Either public key is 33 byte long. I know how to transform a single 33 byte long public into an address. ...
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761 views

When downloading the blockchain for the first time using bitcoind, how do I know when it's done?

I'm using bitcoind on Ubuntu, headless. So there's no GUI to tell me when it's done. So how do I know?
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How to check Bitcoind block chain download progress level

i have installed bitcoind on ubuntu server, and when i run screen -x for btc it says error -10 blockchain is downloading, How do i know the progress level, currently 125600 blocks are downloaded, how ...
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101 views

Blockchain programming books C#?

EDIT 1: It seems that what I really want to learn is how to create software which makes use of a distributed hash table. ORIGINAL QUESTION: I want to learn about coding my own blockchain based ...
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how to parse input script of a transaction in blkzzzz.dat file?

In data files, an input script of a transaction appears to be in this form: [funky byte 1][signature][funky byte 2][public key] Bitcoind displays an input script in this shape: [signature][blank ...
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209 views

Best way to anonymize bitcoin transactions?

https://en.bitcoin.it/wiki/Mixing_service How do sites like this work? "Mixing services". I know it can be broken and traced back with coinsuduko but how exactly does it wash your coins. I doubt they ...
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2answers
87 views

How can I create a list of X richest bitcoin addresses?

I have looked around, but I can't find the code related directly to my question. I want to create a list in any format that contains the all accounts with balance over 0 for example. Thanks ahead for ...
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39 views

Calculating Account Balance [duplicate]

Is anyone familiar with how the standard Bitcoin client gathers account balances from the blockchain? I understand that the software will look through the blockchain to calculate the balance, but I ...
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2answers
46 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 ...
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1answer
28 views

Remove address from sequence in HD wallet

Is there a way to eject an address out of the sequence of an HD wallet? Lets say an address was used for a political donation to a regime in Namibia that may get international condemnation a few ...
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1answer
172 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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81 views

Why wait for several confirmations before shipping?

Suppose customers pay me bitcoins for their purchases. As far as I understand, I could check block chain that the proper payment amount has been made to the address I generate for each customer, and ...
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465 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?
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3answers
610 views

How often forks occur?

How often do forks occur in the block chain? I'm interested in the small, one block forks that happen when two miners create a block at the similar time.
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264 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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3answers
90 views

If using Bitcoin core client am I constantly going to be downloading data from the blockchain?

I understand you have to download the entire blockchain and sync in the beginning but don't you also have to constantly keep the software on if you want to buy/sell stuff, which means more data being ...
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When miners are working on their block, do everybody's block have the same transactions in them?

In this webpage https://en.bitcoin.it/wiki/Blocks, it says this "Bitcoin transactions are broadcast to the network by the sender, and all peers trying to solve blocks collect the transaction records ...
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2k views

get Armory to use an existing blockchain?

I'm trying to set up Armory but it wants to download the whole blockchain. The thing is I already have the blockchain downloaded on the same machine for bitcoin-qt. Is there any way to get Armory to ...
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1answer
2k views

Can the blk0001.dat and blk0002.dat files be deleted?

I have a Bitcoin installation on an SD card, and the blockchain files (blk0001.dat specifically) take up nearly 4 GB of disk space. Can the blk0001.dat and blk0002.dat files be safely deleted to free ...
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108 views

Problem with receiving bitcoins on my VPS

I installed bitcoind v.0.8 on my VPS (with Debian 6 (Squeeze)). Then I generated a wallet for it: 12VWVmNEM1q6N9zMjX9aH3wSfRUbjVkZ21. Here is my transaction to this wallet, but when I'm looking for ...
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43 views

How to store 30kb file using Decentralized Blockchain Data Storage on NXT (nxtcoin) by attach messages?

I'm curious to how would one store a 30kb file on the NXT blockchain since the NXT protocol can attach a 1000byte message. My test scenario is storing a 30kb midi file on the nxt blockchain and then ...
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176 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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Infinitecoin (IFC) transaction delay

A few weeks ago, I made a transaction from an online wallet (coins-e) to my personal (infinitecoin-qt) wallet. Initially I looked for the transaction ID using exploretheblocks for Infinitecoin's ...
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92 views

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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1answer
424 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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739 views

What keeps a dominant Bitcoin client vendor with the majority of the market share from unilaterally changing the protocol?

I've been asking this in the comments, but I'll be more direct. If a third-party Bitcoin client, say "iBitcoin" (for example), becomes the dominant client by acquiring most of the market share, what ...
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1answer
59 views

How does a blockchain store any data?

I read here that since Bitcoin is a networked ledger, it is a good way to back up data. I would like to know two things: How does a blockchain store 'any' data? I would like to know more about a ...
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1answer
72 views

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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2answers
873 views

Do you need to download the entire blockchain in order to mine bitcoins?

Do you need to download the entire blockchain in order to mine bitcoins? I'm downloading bitcoin-qt, and I'm afraid it will take up too much memory on my computer. Also, I just read that when another ...
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1answer
142 views

Retrieving all the funds from BIP32 derived wallets

An ecommerce site is using BIP32 wallets for receiving order payments from a tree of child keys where each leaf node is unique to one purchase transaction. Is it common for the site to immediately ...
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380 views

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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2answers
38 views

Block Chain API for BTC transactions

I want to fetch transactions for an address from the following api: https://blockchain.info/address/$btc_address?format=json The thing is understanding the json returned from the api, I don't ...
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1answer
43 views

Can side chains or “pegged” chains negatively affect the security of Bitcoin?

Regarding the concept of side chains or "pegged" chains which has been discussed since as early as 2011 and explored in this white paper, how can these negatively affect the security of Bitcoin? ...
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What are 'pegged' side chains are and how they will be useful for Bitcoin?

What seems to be a very important paper was released this past week (http://www.blockstream.com/sidechains.pdf). It centers around the idea of 'pegged' side chains, and being able to move coins from ...
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2answers
285 views

Does Proof of Existence lose bitcoins?

http://www.proofofexistence.com/about -- "Use our service to anonymously and securely store an online distributed proof of existence for any document." The document is certified via embedding its ...
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1answer
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What does the main_chain value returned by blockchain.info mean?

What does it mean that for bitcoin block to be on the Main Chain? What other chains are there? Is this as opposed to testnet? This is regarding the main_chain value in the blockchain.info api here: ...
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5answers
22k 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 ...
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1answer
35 views

How to exploit the possibilites of blockchain for proof of authorship?

I want to to create some kind of Proof-of-Authorship mechanism, that's something that many artists had asked before: How can I prove authorship of my work To accomplish my objective I need to deal ...
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1answer
147 views

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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1answer
175 views

Is a full blockchain fork possible?

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 ...
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If I want to run the Bitcoin client from another OS, can I direct Bitcoin to an already downloaded Blockchain on another OS' partition?

I have fast internet, and it wouldn't be too much of a struggle just torrenting the bootstrap.dat, but it would make sense to make use of an already existing blockchain and save space and time. I've ...
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Is it possible for corporate interests to incentivize securing alternate Blockchains instead of Bitcoin's Blockchain?

Is it possible for corporate interests to incentivize securing POW of alternate blockchains instead of Bitcoin's blockchain? Given the large amount of funding and/or "partnerships" announced the last ...
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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 ...