Questions tagged [bitcoin-core]

This tag should be used for questions pertaining to Bitcoin Core. Bitcoin Core is an MIT-licensed Qt 5 GUI application for the original Bitcoin codebase. Additional/previous names include "Bitcoin-Qt", "Satoshi-Client", and "Standard Client". This tag should be used when referring to the Bitcoin Core software.

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How do I import a private key into Bitcoin-Core?

How do I import a private key into Bitcoin-Qt? bitcoind is nowhere to be found, and pywallet says it requires "bsddb" when I run it, which is also nowhere to be found. I generated some vanity ...
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43 votes
2 answers
77k views

How can I export the private key for an address from the satoshi client?

If I want to transfer an address from the satoshi client into a different client, how can I find its private key to do so?
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21 votes
4 answers
25k views

How can I setup Bitcoin to be anonymous with Tor?

Bitcoin is billed as many things, among them its anonymity is highly regarded. While it is true that a transaction does not identify a user or wallet, recent news shows that there is the potential for ...
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42 votes
4 answers
74k views

Where is the data folder for Bitcoin-Qt?

Where can I find the blockchain, wallet.dat, etc. on each of the operating systems Bitcoin-Qt supports?
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22 votes
5 answers
45k views

Bitcoin-Qt setup: Change block-chain file location, settings? documentation?

I am installing Bitcoin-Qt and have been reading about Bitcoin basics, but I found very little information on the client. I have a few questions about the Bitcoin-Qt program (v0.8.1-beta under Windows ...
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  • 323
18 votes
3 answers
18k views

Are there Bitcoin password crackers I can use to recover forgotten passwords?

I've lost the password to one of my wallets (it's a small one, don't worry). I was sure I remembered the password ... but evidently I don't. Is there a program that I can use to brute-force my ...
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49 votes
4 answers
196k views

Import wallet.dat into a new Bitcoin-Qt client

I had Bitcoin-Qt on my computer with several bitcoins in my wallet, using Vista. Then my computer crashed. Finally I was able to get my computer fixed and download a new version of Bitcoin-Qt. Now I ...
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  • 491
20 votes
5 answers
28k views

Sync with bitcoin-qt very slow (0,01%)

I have the issue that my node's synchronisation is very slow. I am 14 weeks behind and it estimates to take 12 weeks to get synced. The synchronisation rate per hour is only 0,01%. I have a fast ...
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  • 301
24 votes
1 answer
14k views

Why the signature is always 65 (1+32+32) bytes long?

A signature created by the Bitcoin-Qt client can always be decoded (base64) to a 65-byte array. This array seems (according to https://github.com/bitcoin/bitcoin/blob/master/src/key.cpp#L217) to ...
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  • 2,701
6 votes
4 answers
11k 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?
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  • 211
33 votes
1 answer
53k views

How can I restore my wallet?

I just purchased a new laptop and I want to decommission my old one. I have a back-up of my wallet.dat file copied to my new PC. What do I need to do to restore it to my Bitcoin (Windows) client? ...
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16 votes
1 answer
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How does "Sign Message" work?

How does "Sign Message" option in the Bitcoin QT client work? I can't find any description or documentation of it. Do I have to use this option to sign some message when I receive bitcoins? If so, ...
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  • 263
5 votes
2 answers
2k views

HTLC (Hash Time Lock Contract) using bitcoin-qt

Is it possible to manually create a HTLC using the bitcoin-qt command line? I know how to manually creating createrawtransaction/sendrawtransaction using the bitcoin-qt clients command line, and ...
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23 votes
4 answers
36k views

How do I import private keys from Bitcoin-qt to Multibit client?

Question says it. I spent 20 mins Googling. Saw several links on bitcointalk.com but amazingly found no solution to this. Am I the first one trying to do this? Note the following are not the ...
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16 votes
5 answers
26k views

How can I transfer a Bitcoin-qt wallet to Electrum?

I am switching from bitcoin-qt to Electrum, and it seems as if I will need to download the blockchain again. Can I copy and paste my wallet.dat into Electrum's files?
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  • 161
11 votes
1 answer
3k views

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 ...
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30 votes
2 answers
32k views

How exactly does -rescan work?

-rescan is a command line argument that is passed to the bitcoin client after restoring wallet.dat from backup. Which files get recalculated? Which files does the rescan command read? Why is it a ...
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12 votes
1 answer
13k 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....
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5 votes
9 answers
8k views

Is there logically any way to "live off of Bitcoin interest" without giving up control of your coins?

All my life, I've been told that rich people don't need to spend any of that wealth. Instead, they just have a bank account where they receive a percentage of the total sum on the account every year ...
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29 votes
2 answers
17k views

How can I combine all the tiny amounts I've received to minimise transaction fees, and do I need to?

Important parts in bold, for those who don't want to read the detail! I've received lots of tiny transactions, in amounts sometimes as low as 0.000003BTC. Even though I've also received (relatively) ...
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13 votes
2 answers
8k views

How to run bitcoind in a low memory environment

I have a Raspberry Pi with 925 MB of memory. Bitcoin Core, operating as a full node, uses between 600-900 MB. How can I reduce bitcoind's memory usage? I tried setting maxmempool to its minimum ...
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  • 4,307
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 ...
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  • 313
13 votes
3 answers
8k views

What is the exact formula for calculating transaction fees?

According to the Wiki: If the blocksize is more than 250 kB, transactions get increasingly more expensive as the blocksize approaches the limit of 500 kB. Sending a transaction when the blocksize ...
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9 votes
2 answers
4k views

Is there a way to change the wallet.dat location without changing the entire data directory?

I know that Bitcoin supports the -datadir command line option which specifies that the wallet.dat and blockchain should be stored in a custom location rather than %appdata%\roaming\bitcoin but is ...
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6 votes
1 answer
2k views

Get notified of incoming Bitcoin transaction, as soon as it broadcasted

After a few weeks of searching for an answer, I decided to ask here. I want to accept a Bitcoin payment, to a specific wallet, and immediately, when the user approved the payment, to receive an ...
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2 votes
1 answer
1k views

What is the length of largest known reorganization in bitcoin? [duplicate]

Usually there is an assumption, that a transaction is fully finalized after 6 confirmations, e.g. 6 blocks mined on top of the block, which includes given transaction. What is the length of largest ...
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10 votes
2 answers
9k views

What does Bitcoin Core's "Coin Control Features" do and how do I use it?

What is Bitcoin Core's "Coin Control Features"? How do I use it, and what can I do with it?
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9 votes
2 answers
2k views

Is there developer documentation for the Bitcoin Core source code?

Is there a documentation somewhere to understand the C++ code of Bitcoin Core (available on Github) "from a to z" and being able to recreate it ?
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  • 305
1 vote
2 answers
10k views

How to activate the mining process in the standard bitcoin client?

I have done the whole synchronization and now it should be mining bitcoins from what I understand but I don't see anything showing that it is actually mining for bitcoins nor any activity from my cpu… ...
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  • 21
1 vote
1 answer
2k views

Bitcoin Mining as a Newbie (link wallet to another person's miner) [duplicate]

I'm new in bitcoin mining. I would wish to mining to make some profit. I have just talked to someone and he has told me I can partner with him to use his miner. I have some bitcoins ready with me and ...
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22 votes
1 answer
17k views

Get non-wallet transactions using bitcoin rpc (gettransaction)

I am playing around with Bitcoin-qt. I want to iterate all blocks and all their transactions. So far I've been able to get a list of all tx's in the blocks I want to. Now I want to get information ...
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24 votes
2 answers
14k views

Bitcoin URL scheme

What is the URL scheme that is used by Bitcoin to copy transaction information directly into the client? Which versions of Bitcoin clients support it?
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16 votes
1 answer
16k views

How do I specify in which directory Bitcoin blocks and other data should be stored? [duplicate]

I am on Windows and installed the Bitcoin wallet. The block folder seems to grow bigger everyday and is stored on my C drive in the roaming directory. I would like to set this to some other folder on ...
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17 votes
2 answers
10k views

What are the safety guidelines for using the Sign Message feature?

bitcoin-qt's dialog box states, "Be careful not to sign anything vague, as phishing attacks may try to trick you into signing your identity over to them. Only sign fully-detailed statements you agree ...
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  • 5,451
9 votes
1 answer
16k views

How do I configure Bitcoin Core to connect always to a particular node?

By reading https://bitcoin.org/en/full-node I've decided that I want to run a FULL node (let's call it 'X'), to contribute to the P2P network. So, I'll leave its ports open, or have a DMZ zone with a ...
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  • 1,668
5 votes
5 answers
21k views

My client stopped synchronizing, how can I access my wallet?

My wallet has been stuck synchronizing for 21 days, my transfer is in the block chain but I can't get it to sync with my wallet. I've closed firewalls, uninstalled and reinstalled QT with back up and ...
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  • 51
4 votes
1 answer
2k views

dumpwallet output documentation & explanation?

Where do I find complete documentation on what the console command "dumpwallet" output means? Sample of my testnet output: # Wallet dump created by Bitcoin v0.21.0 # * Created on 2021-01-...
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  • 164
10 votes
3 answers
36k views

How to resolve "no block source available"?

I've got some trouble using bitcoin-qt. It stays on: "No block source available... 242 weeks behind." And "Catching up ... Processed 0" etc... Map port using UPnP is activated, and proxy disabled ...
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  • 101
8 votes
2 answers
5k views

Can wallets be shared by different machines?

I have a bitcoin client installed on machine one. Let's say it has 5 coins in there. I then have another machine, with another client on it. Can both machines see the same wallet? Do I have to have a ...
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  • 81
8 votes
2 answers
8k views

Backing up my bitcoin wallet - is wallet.dat all I care about?

I know that there are many duplicates of this but I'm hoping that the way in which I word this explains and helps not just me, but others as well. In any of the coin wallet bitcoin and the alt coins,...
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4 votes
1 answer
1k views

"New rules activated" warning after upgrading to 0.20.0

I've upgraded a node from the previous release. It's up and running but for some reasons I get this warning. How can it be related to the upgrade? $ bitcoin-cli -testnet getblockchaininfo | jq { "...
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  • 43
2 votes
1 answer
556 views

How can I get address's balance that doesn't belong to my Bitcoin core wallet?

I have been looking for a way to see the address's balance that doesn't belong to my own Bitcoin core wallet. I don't like to use an external API, I have this full node and I really wonder if this is ...
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9 votes
1 answer
859 views

What are the trust assumptions in --assumed-valid in bitcoin core 0.14?

Please help me understand and distinguish the trust assumptions in the following three cases shown below. Specifically, please elaborate the attacks possible (even though completely theoretical) and ...
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  • 1,224
8 votes
1 answer
15k views

How do you apply "-zapwallettxes" on Windows?

On May 27 I tried to sell some Bitcoins(for the first time). Since that day the transaction is in the status "unconfirmed". The amount is booked from my wallet, but isn't booked to my bank account. ...
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  • 81
2 votes
1 answer
3k views

How to get xpub or mpk(bip32) for my bitcoin core wallet?

I m not getting any such option in bitcoin-core Ui and documentation http://bitcoindaily.org/bitcoin-guides/bitcoin-core-tutorial/
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2 votes
2 answers
2k views

How do I get rid of an unconfirmed transaction on Bitcoin Core 0.14.1?

Can somebody please help me? I have been trying to send .045 Bitcoins (approx $120 USD) I am using Bitcoin Core. I have tried to get rid of the unconfirmed transaction by using -zapwallettxes ...
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1 vote
2 answers
132 views

1 MB Block Size as a Anti-DoS Attack Measure

Wikipedia explains the rationale behind the 1 MB block size limit as follows: The one megabyte block size limit was added in 2010 by Satoshi Nakamoto as a temporary anti-DoS measure A SE post ...
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  • 399
0 votes
1 answer
79 views

What can I expirement with BitcoinCore on my own?

I have a simple faculty assignment where I have to do some experiments with transactions or experiment with the Bitcoin protocol or maybe with wallet code. Work on that assignment shouldn't last more ...
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  • 449
0 votes
1 answer
124 views

Bitswallet core

Please does anyone know how to synchronise bitswallet with network. Have been trying to synchronise mine with network. But it does not seem to be synchronising with the network. I need help fixing it. ...
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20 votes
2 answers
47k views

How to use the "Bootstrap.dat" file with bitcoin-qt?

I have searched around, and nothing I find works for me. Downloaded the approx. 10 GB Bootstrap.dat file. Now stuck on trying to link it with Bitcoin-QT. Tried the following command in the console ...
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