text:
Compiling bitcoin-core from source Ubuntu 17.10
Hey everything has usually been fine compiling from source until i updated to Ubuntu 17.10
I've configured using --disable-wallet and i'm using the most up to date master branch
chris@chris-GE60-2PL:~/bitcoin$ sudo make
Making all in src
make[1]: Entering directory '/home/chris/bitcoin/src'
make[2]: Entering directory '/home/chris/bitcoin/src'
make[3]: Entering directory '/home/chris/bitcoin'
cd . && /bin/bash ./config.status src/config/bitcoin-config.h
config.status: creating src/config/bitcoin-config.h
config.status: src/config/bitcoin-config.h is unchanged
make[3]: Leaving directory '/home/chris/bitcoin'
make[3]: Entering directory '/home/chris/bitcoin'
make[3]: Leaving directory '/home/chris/bitcoin'
make[3]: Entering directory '/home/chris/bitcoin/src/secp256k1'
make[3]: Leaving directory '/home/chris/bitcoin/src/secp256k1'
  CXX      libbitcoin_util_a-clientversion.o
  AR       libbitcoin_util.a
  CXXLD    bitcoind
  CXXLD    bitcoin-cli
  CXXLD    bitcoin-tx
  CXXLD    test/test_bitcoin
  CXXLD    bench/bench_bitcoin
  CXX      qt/qt_libbitcoinqt_a-moc_bitcoingui.o
qt/moc_bitcoingui.cpp: In static member function ‘static void
BitcoinGUI::qt_static_metacall(QObject*, QMetaObject::Call, int,
void**)’:
qt/moc_bitcoingui.cpp:217:21: error: ‘class BitcoinGUI’ has no member
named ‘setEncryptionStatus’; did you mean ‘setDockOptions’?
         case 6: _t->setEncryptionStatus((*reinterpret_cast< int(*)>
(_a[1]))); break;
                     ^~~~~~~~~~~~~~~~~~~
                     setDockOptions
qt/moc_bitcoingui.cpp:218:21: error: ‘class BitcoinGUI’ has no member
named ‘setHDStatus’; did you mean ‘setStatusBar’?
         case 7: _t->setHDStatus((*reinterpret_cast< int(*)>(_a[1])));
break;
                     ^~~~~~~~~~~
                     setStatusBar
qt/moc_bitcoingui.cpp:219:33: error: ‘class BitcoinGUI’ has no member
named ‘handlePaymentRequest’
         case 8: { bool _r = _t-
>handlePaymentRequest((*reinterpret_cast< const SendCoinsRecipient(*)>
(_a[1])));
                                 ^~~~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:221:21: error: ‘class BitcoinGUI’ has no member
named ‘incomingTransaction’
         case 9: _t->incomingTransaction((*reinterpret_cast< const
QString(*)>(_a[1])),(*reinterpret_cast< int(*)>(_a[2])),
(*reinterpret_cast< const CAmount(*)>(_a[3])),(*reinterpret_cast<
const QString(*)>(_a[4])),(*reinterpret_cast< const QString(*)>
(_a[5])),(*reinterpret_cast< const QString(*)>(_a[6]))); break;
                     ^~~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:222:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoOverviewPage’
         case 10: _t->gotoOverviewPage(); break;
                      ^~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:223:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoHistoryPage’
         case 11: _t->gotoHistoryPage(); break;
                      ^~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:224:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoReceiveCoinsPage’
         case 12: _t->gotoReceiveCoinsPage(); break;
                      ^~~~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:225:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoSendCoinsPage’
         case 13: _t->gotoSendCoinsPage((*reinterpret_cast<
QString(*)>(_a[1]))); break;
                     ^~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:226:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoSendCoinsPage’
        case 14: _t->gotoSendCoinsPage(); break;
                      ^~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:227:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoSignMessageTab’
         case 15: _t->gotoSignMessageTab((*reinterpret_cast<
QString(*)>(_a[1]))); break;
                      ^~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:228:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoSignMessageTab’
         case 16: _t->gotoSignMessageTab(); break;
                      ^~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:229:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoVerifyMessageTab’
         case 17: _t->gotoVerifyMessageTab((*reinterpret_cast<
QString(*)>(_a[1]))); break;
                      ^~~~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:230:22: error: ‘class BitcoinGUI’ has no member
named ‘gotoVerifyMessageTab’
         case 18: _t->gotoVerifyMessageTab(); break;
                      ^~~~~~~~~~~~~~~~~~~~
qt/moc_bitcoingui.cpp:231:22: error: ‘class BitcoinGUI’ has no member named ‘openClicked’; did you mean ‘optionsClicked’?
     case 19: _t->openClicked(); break;
                  ^~~~~~~~~~~
                      optionsClicked
Makefile:7129: recipe for target 'qt/qt_libbitcoinqt_a-moc_bitcoingui.o'
failed
make[2]: *** [qt/qt_libbitcoinqt_a-moc_bitcoingui.o] Error 1
make[2]: Leaving directory '/home/chris/bitcoin/src'
Makefile:9361: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/chris/bitcoin/src'
Makefile:746: recipe for target 'all-recursive' failed
make: *** [all-recursive] Error 1

Can you please clarify what exactly you're asking... is it how to fix the error?

Welcome to Bitcoin.SE! Can you please state what platform you are compiling for?

Do make clean then rebuild.
If that doesn't work, reconfigure (./autogen.sh and ./configure) then make clean again, then make.

It is usually better to build a tagged version than from just off the top of master which may have additional changes.
More recently there were some dependancy changes[1].
In the /bitcoin directory you need to:
sudo apt install zlib1g-dev
git clean -fdx

Get on the master branch:
git checkout master

Pull down the current master including tags. Depending on how you are configured, how to do this will vary but could be as simple as git pull origin --tags
Then, you should definitely check out a tagged version. The current highest tagged version as of writing is v0.16.0 - you can check what tags exist with git tag - I usually do that this way into a branch:
git checkout v0.16.0 -b v016

Then, follow the specific build instructions in /bitcoin/doc/*.md. For example, Ubuntu 17.04 is specifically supported in build-unix.md
rel:
[1] github.com - "Ok, I've identified the issue. It is because one of the dependencies ..." - https://github.com/bitcoin/bitcoin/issues/12515#issuecomment-368283657


text:
Have I lost all my Bitcoin, having sent them to a Bitcoin Cash wallet?
I made a pretty big mistake of sending my Bitcoin that I had on Coinbase to a Bitcoin Cash wallet that I own on my Exodus wallet instead of the Bitcoin wallet. I can see on Coinbase that the address it went to is the Coinbase Cash wallet that I have on Exodus and the transaction has now been completed, but nothing appears in Exodus.
I understand that sometimes this can be ok depending on the address format and I'm not entirely sure how long it is supposed to take until you see it. Do I take it that I've just lost all those coins since they haven't appeared at all? Also if so where do those coins go?

Keys are interchangeable on both chains. If you export the private key of the address you sent it to on the bitcoin cash wallet , and import it back into another wallet (Exodus for Bitcoin?) , you should see your bitcoins.

I would upvote your answer if you would elaborate a bit on the "import it back" part of your answer.

Bobo is correct
The private key on Bitcoin Cash is identical to the private key on Bitcoin.
So, just import the seed phrase from your Bitcoin Cash wallet into a Bitcoin wallet.  Your funds will be there
If there is a address compatibility issue, just use a different wallet, such as Coinomi, it has good compatibility

I must not be understanding this, because it sounds like  a way to get infinitely rich.  I have some Bitcoin Cash with private key "A".  I send it to a different Bitcoin Cash address with private key "B".  I import the key "B" into a Bitcoin wallet and claim the BItcoins.  Then I send my Bitcoin Cash to a new Bitcoin Cash address with private key "C".  Then I import the key "C" into a Bitcoin wallet and claim the Bitcoins.  Repeat forever.  What have I thoroughly misunderstood here?

The coins never leave the chain, the keys are just the same.  So, if you send the coins (on Bitcoin) to a Bitcoin Cash address, you have really just used an identical Bitcoin address which you now also control, since your Bitcoin Cash seed phrase can be used on Bitcoin.  Bitcoin uses the same key infrastructure, so you can control any Bitcoin addresses you have BCH keys for. Ordinarily this is useless, but in this case it can recover the funds

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Why not issue all the Bitcoins at once
What is the point of mining the Bitcoin and thus issuing new Bitcoins over the span of some time versus simply issuing all 21 million coins at once?

Ask yourself this .... if they were all issued at once, who would they be issued to?

Would be great if it was me.

If they were all issued to you, they would be worthless. A currency's value comes from its being useful as a medium for multipe parties.

That was a bad joke.

In a way, all bitcoins were issued with the genesis block: The total number was fixed and the distribution schedule defined with the rules put in place then. However, distributing them over a longer period of time allows for the bitcoins to be spread out more, creates incentives for miners to contribute work to the Bitcoin network and probably also helped fewer of them getting lost during the emergence of Bitcoin when many people just tried it briefly and likely didn't properly store their coins.

Good points....

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Recover BTC sent to a BCC address
I accidentally sent my BTC to a BCC address. Is there a way to recover them? Is there somebody that can help me with this matter? If there is a charge to recover my coins, I will pay for it.


text:
Segwit address creation
I'm unable to create a segwit address in Bitcoin Core 15.0.1 64-bit Windows
I have tried multiple times but keep getting the same error.  The following is the output from the console
$ getnewaddress
1KxN5zBSMqCiMfaXpbgpbDipo3fdrWmWnF
$ addwitnessaddress 1KxN5zBSMqCiMfaXpbgpbDipo3fdrWmWnF
Public key or redeemscript not known to wallet, or the key is uncompressed (code -4)

I have also tried changing my encryption password but it did not help.  I do not want to create a whole new wallet.  What else can I do?  Thanks

Can you post the output of the getwalletinfo command? The address likely corresponds to an uncompressed public key so it cannot be witnessified.

Your wallet is probably old enough that uncompressed public keys are used instead of compressed public keys. Segwit only works with compressed public keys so you cannot currently use segwit with your addresses.
However you can upgrade your wallet to using compressed keys. To do so, first start Bitcoin Core with the -upgradewallet option. That will upgrade your wallet to use compressed keys by default. Then you will need to call getnewaddress ~1000 times in order to get to addresses using compressed public keys keys. I don't believe that there is a way to regenerate the keypool without emptying it by requesting all of the addresses from the keypool.

Yes my wallet is from 2012.  So the "getnewaddress" command will give me about 1000 receive address.  Is there a way to delete some of my receive address?  Thanks for you replay

No, addresses cannot be deleted.

Seems like it would be best if I would backup my wallet.dat and delete form the from "C:\Users\user\AppData\Roaming\Bitcoin" folder and have it create a new one.  The new then should be able to create segwit address.

Yes. You can move all of your coins there by getting some addresses from the new wallet and sending your Bitcoin to those addresses from your old wallet. This also has the benefit of migrating your wallet to the HD wallet type where one backup can theoretically backup all of your private keys ever, although periodic backups are still recommended.


text:
Does my Electrum wallet become less secure if I keep generating seeds until I see one I like the look of?
Let's say I want to create a new electrum seed... I didn't like the initial seed words, since I want to remember them and these didn't look too appealing. Looking "too random" for my taste. When I repeat this process like 100 times, chances are that I like the combination then more, because it looks "less random" or "more logical to me" (looking like a short story being summarized) which is easier to remember.
Is doing this insecure? Do I increase my risk of randomly creating a not-so-random seed by redoing the seed creation until I get a seed that I like?

No, this does not reduce your security. You are not choosing a seed to use that is not random, you are still allowing the random number generator to create a seed for you which you then chose. There is still sufficient randomness in this process as the seed is still randomly generated.

Yes, this does reduce your security. The fact that the seed words were generated randomly becomes meaningless if you use a non-random process to select the seed that you actually use. For instance, it is entirely possible (though very unlikely) that a random password generator would generate a phrase such as "Columbus sailed the ocean blue in 1492". You might say gee, what luck - that is a great password to remember, I'll use that one. Yet, a password cracker that tries meaningful phrases before moving on to random strings will be able to crack this password in the initial phase, even though the probability of randomly generating such a phrase is the same as for any other character string of the same length.

why the down vote? even though op's process might not be too bad, other practices like looking for a word (words) that have special meaning to you might not be the greatest idea.


text:
Should you protect your Bitcoin address like your credit card number?
Today, I recieved this scam email:

We have reached the biggest milestone in our history – over a million wallets.
https://[removed] will celebrate with some big prizes.
In October 2013, the lucky user who created the 500,000th wallet was rewarded with 10 BTC.
Read more about this: http://[removed]
We have discovered that you created the wallet with number 1.000.000
[removed] want to reward you with 50 BTC.
To prove that you are the rightful owner of the lucky wallet,
     please reply to this email and send us your mnemonic ( the long string of words generated randomly when your account was created)
After verification, your wallet will be credited instantly with the 50 BTC.
Thank you that you have chosen https://[removed]

I am guessing this is a scam as (a) it was sent to two separate email addresses I have, (b) the sender's email is in no way affiliated to the websites listed in the email and (c) I don't think anyone is willing to just give away 50 BTC which is close to $42,000 USD. I was wondering if I were to give them my Bitcoin address, what would happen next? Would they be able to use it like a credit card number? Or would they just be asking for more personal information?

A bitcoin address is not like a credit card number. You can safely give your bitcoin address out publicly.
What the email is asking for is something you should never give out publicly: the mnemonic that you use (e.g. if you use Electrum, they have a 12-word mnemonic code), from which you can calculate your private keys. With this, they can easily steal all bitcoins on any address that was generated using that mnemonic.
If they actually wanted to know that you are the owner of an address, they could ask you to sign a message. There's not normally much of a reason to do this, though: I don't see a scenario in which a signed message is needed in order to give you money, instead of just the address.
If they actually just wanted to send you money (as they claim), all they need is your address.

A legit reason for verifying the adress first is to prevent sending 50 BTC into nirvana, when you don't have the private key for the adress anymore.

Giving away your public address wouldn't be the same as giving away your credit card. But what I think the sender of this email is might be trying to do is the following:

Collect BTC loaded public addresses.
Run (with brute force) common phrases, or even with common words to crack it
Collect any BTC with addresses which have weak private keys.

If I would have done this, I would have used vanitygen to verify the common passwords (private keys), against the public addresses. Given that you can check 60k-300k private keys per second (with an i5 core), it'll be fairly easy to check all of the submitted addresses.
-Besir

Even simpler, the scam is simply asking for the original seed used to generate a deterministic private key. No brute force needed, they'll simply steal your money if you give them what they ask for.


text:
Is there a Trading API that spans multiple independent sites, preferably from open source websites?
To experiment a little with automatic trading I'm looking for a trading api (like mtgox has) which is used on multiple independent websites so that if one goes under that I then don't have to redo my whole program. If possible one from open source bitcoin trading websites so that I can setup one in a vm and use that to test against.
I'm currently running my tests against Mt.Gox but that can be a bit expensive when the script doesn't perform too well.

The Java XChange library could help
It might not be exactly what you're after, but the XChange project provides a demonstration of a general purpose API for communicating with multiple exchanges.
You could repurpose the code to create your own mock trading endpoints and run up a collection of virtual hosts. In this manner you can test against a reasonably well known set of APIs for the usual failure modes.

goxcli could also be an interesting codebase to make your own multi exchange trading api, goxcli provides an interesting and a shell api you can use as a backend to build your own frontend on top of it. for no goxcli supports only mtgox, but its open source and you can fork it on github : https://github.com/Trasp/GoxCLI
see also : https://github.com/neofutur/bitcoin_simple_php_tools


text:
Why does calling BlockExplorer's checkaddress JSON API do nothing?
I need some help with using JSON and the bitcoin / blockexplorer json calls. I'm not even sure if this is going to work. Basically I'm trying to validate a bitcoin wallet address. I want it to check against the blockexplorer to see if it's a "valid" address or not.
Here's what I've done so far:
function checkAddress(){
  var address = $('#wallet').val();
  $.getJSON('http://blockexplorer.com/q/checkaddress/'+address+'?format=json',{"format":"json"},function(data){
    alert('xxx == '+data);
  });
}

But it doesn't seem to be doing anything at all.. Is it even possible for me to use the blockexplorer with JSON to get the results? I'm incredibly new to bitcoin and I'm not entirely sure what I'm doing.

You are trying to cross domains.
Look into jsonp for that:

https://github.com/jaubourg/jquery-jsonp

Don't cross the streams!


text:
Should the current value of 1 BTC really be $2.50 USD?
The real value of a currency depends on the value of the goods that can be purchased with it. If we assume the majority of bitcoin transactions for 'real' goods (not  currency speculation) are on silk road we can do the following calculation.
The demand in USD is about 1.9 million per month (http://arstechnica.com/tech-policy/2012/08/study-estimates-2-million-a-month-in-bitcoin-drug-sales/)
which works out to be $63,333 per day (the demand)
There are currently 10118337 bit coins that have been created and each coin is spent on average once every 399.357 days (http://abe.bitcoinstats.org:2750/)
This means that each day there are 10118337 / 399 = 25,359 bitcoins available to use for transactions each day (the supply)
The price of 1 BTC should then be supply / demand =  $63,333 / BTC 25,359 = $2.49 USD per coin
Does anyone have alternative suggestions for calculating the price or is Bitcoin in a bubble?

It appears you are trying to come up with the valuation based on the velocity of money, but aren't making a clear case. The largest number of transactions are for online gambling, so that's one instance of demand for coins.

Thanks Stephen, how would I find out the largest number of transactions are for online gambling? All the reading I've done points at silk road being the main place coins are spent.

As famous as it is, I believe Silk Road isn't the reason for Bitcoin's existence or its success.
There are plenty of private individuals who value Bitcoin for international money exchange,  its low cost trading capability, its irreversability, its lack of a central authority and its upper limit on the number of bitcoins.
If you analysed the transactions over time and experimented with deposits to various exchanges and traders, you would be able to build a partial picture of who is holding the existing bitcoins. You might be able to determine an upper limit on how many bitcoins are being held by speculators.
However, the value of Bitcoin as a system is dependent on its popularity, so current events can have a strong effect on the value.
Realistically, the best way to value a bitcoin is to look at the market price over time on a major exchange.


text:
How can I work with multiple testnets?
Apart from running a private testnet-in-a-box there are also the public testnet instances. You can use this instead of the regular (production) bitcoin network by setting testnet=1 in your bitcoind configuration file. However, the fact that there are multiple instances and not just one testnet can be confusing.
Is it my version of bitcoind that determines which testnet I am on, or something else?
How can I see which testnet I am using?
Is it possible to switch testnet? If I was on testnet 2 and wanted to use testnet 3 would it require upgrading bitcoind? Would upgrading bitcoind automatically bring me over on the new testnet, deleting all my old blocks, transactions and coins from the old one?
Are there other bitcoin clients that support testnet and if so which one(s) do they use?
If I want to use blockexplorer or something similar, do they only support the "latest edition" testnet?

If you are using Bitcoin version 0.7, you are on testnet 3. Updating to that version will put you in the newest testnet. Blockexplorer and Testnet Faucet use that version.


text:
Why is my client saying "A fatal error occured. Bitcoin can no longer continue safely and will quit. "?
i am running bitcoin client on OSX. I am by no stretch of the imagination any good at using terminal. I had over 300 btc in there and my computer went black and now client keeps giving me this message "A fatal error occured. Bitcoin can no longer continue safely and will quit.
EXCEPTION: 22DbRunRecoveryException
DbEnv::open: DB_RUNRECOVERY: Fatal error, run database recovery
bitcoin in Runaway exception
"
I can pay somebody to help me fix this problem. dont want to lose the coins i have there. thanks. you'll have to bear with me though. not too good at this.

If you don't already have a backup of your wallet.dat file, make one now. If you do already have one, make another but don't overwrite the old one with this one. So long as you have some file that contains your private keys, you will ultimately be able to recover the coins.

And be cautious if you proceed to hire someone to help.

That alone doesn't provide enough information to know which database file the error is occurring with.   The debug.log might give a more precise indication.
If it is a problem with the blockchain, that is easily resolved.  If the problem occurred after your computer crashed, that is likely what happened.
First though check to eliminate that the problem is that your hard drive partition is filled with no disk space remaining.  That probably isn't the case on your Mac, but just in case, check first.
So, after making yet another backup up your wallet.dat, then you can do this to get a new copy of the blockchain:
These instructions are for mac.  For Linux and Windows the directory names would be different.
 $ cd ~/Library/Application Support
 $ mv Bitcoin Bitcoin-bak
 $ mkdir Bitcoin
 $ cd Bitcoin
 $ cp ../Bitcoin-bak/wallet.dat .

Then launch Bitcoin-Qt as normal.  It will re-download the blockchain.  This could take 24 hours or more, depending on a number of factors.
You might speed that up a bit by getting the blockchain as-of block 170,000 from here:

http://sourceforge.net/projects/bitcoin/files/Bitcoin/blockchain

After it downloads, extract those files into your new ~/.bitcoin directory.
If after Bitcoin-qt downloads the blockchain to the most recent block and everything works fine (shows your wallet balance and transactions properly), you can then remove the .bitcoin-bak directory:
$ cd ~/Library/Application Support
$ rm -rf Bitcoin-bak

Also, the blockchain download is faster if you are on the most recent release of Bitcoin-Qt, v0.6.3.

I am embarrassed to say that I cannot even find the wallet.dat file. like i previously stated I am a complete novice and cannot navigate terminal well at all. I am following what i have read as best i can and keep getting terminal messages that say there is no such file.

but i would like to say thank you to you guys thus far. really appreciate it

Oops, I had the wrong directory names, ... Mac is different.  Updated the post.  Try again please.

Also, I added a note about the disk space.  Just check that the disk isn't full -- that could cause this as well.

got terminal working. buuuuut it still doesnt think there is a wallet.dat file: miltons-MacBook-Pro:Bitcoin milton$ cd ~/Library /Application Support
miltons-MacBook-Pro:Library milton$ mv Bitcoin Bitcoin-bak
miltons-MacBook-Pro:Library milton$ mkdir Bitcoin
miltons-MacBook-Pro:Library milton$ cd Bitcoin
miltons-MacBook-Pro:Bitcoin milton$ cp ~/Bitcoin-bak/wallet.dat .
cp: /Users/milton/Bitcoin-bak/wallet.dat: No such file or directory
miltons-MacBook-Pro:Bitcoin milton$

thanks again for all th help. still havent fixed it but i think i am on the right path, as everything worked except the last command line

Sorry, fixed my typo.  Try this:
$ cd ~/Library/Application Support/Bitcoin
then
$ cp ../Bitcoin-bak/wallet.dat .

should i try these two command lines after, $ cd ~/Library/Application Support
$ mv Bitcoin Bitcoin-bak
$ mkdir Bitcoin
$ cd Bitcoin

I'm sorry, stack exchange comments suck as far as communicating.  If you'ld like further assistance, please request help in the #bitcoin IRC channel: http://webchat.freenode.net/?channels=#bitcoin


text:
Help sending bitcoin to bitcoincash wallet
I've used an UPHOLD wallet to buy an AntMiner S9 from www.bitmain.com.
Bitmain provided a bitcoin cash address for payment.  However, by mistake, I sent bitcoin worth $1450 USD to their bitcoin cash wallet. Now, they have not confirmed the payment. And now I do not know what to do?  Where is my money?
Uphold gave me a BlockChain confirmation address and the transfer appears but as (not spent).  Neither bitmain.com nor Uphold has given me any reply.
I did this on Friday, November 17 and today, Monday, November 20, I have not received a response.
What should I do?  Can someone help me? I cannot afford to lose $1450 USD.

If you control both the sending (BTC) and receiving (BCC) wallets, you can recover the money by restoring the private key from the BCC wallet into a new wallet created on the BTC BlockChain.  Unfortunately, in this case it appears you have sent money to a BitCoin Cash wallet you do not control.
If you do not control the receiving address, sending a Bitcoin payment to a Bitcoin Cash address will almost certainly result in total loss of the money sent to the Bitcoin Cash address.  When you send Bitcoin, you are sending it to another address on the Bitcoin BlockChain.  There is no built-in method of sending Bitcoin to Bitcoin Cash directly; you should convert the Bitcoin into currency, then purchase Bitcoin Cash with that currency, typically through an exchange.
If you do not own the receiving wallet, the only way to get that money back would be in the highly unlikely event you sent it to an address that happens to exist in the Bitcoin BlockChain, and the person who owns that Bitcoin address decides to be nice, and send the money back to you.
As always, it pays to understand how a currency works by using a small amount of money at first.  You wouldn't give your 4 year old $1,500 to play with, would you?

Hello, thanks for answering. The money in bitcoin was sent to a wallet of the company bitmain.com and this was to buy an antminer s9, I got it in a page that gives me uphold.com to confirm my transfer in blockchain which are these:
ID DE LA TRANSACCIÓN EN RESERVECHAIN
ed6fdc73-796d-48a7-881f-b8307188594f
Transacción llevada a cabo utilizando Uphold Android Wallet
ción?
View sources
BLOCKCHAIN TRANSACTION ID
322855dabca7f30e3389d5a1f22426cc06c68c6dfe7bc8b4ecd27b30e817f2d2
But I do not understand.


text:
Unable to Connect Trezor
My trezor worked fine until the other day it wouldn't connect.  I tried myehterwallet, trezor app in Chrome, and the trezor.io site--nothing.  I've tried using different cables, different computers, different usb ports and even followed the trezor instructions for emergency reset.  Nothing is working to open my Trezor and allow access to my currency stored on it.

I don't see any question. We can't help you fix broken hardware.

You should have your Trezor recovery card with 24 words you have written down. With these 24 words (the recovery seed) you can access your coins without a Trezor. Here is an explanation.
If this doesn't help you might want to contact Trezor support.


text:
How do miners handle transactions when a different miner creates a new block?
If all transactions are broadcast to all nodes, and all nodes are mining these transactions into blocks.  When a block is created and the block is broadcast to all nodes, it may contain transactions that other nodes are currently trying to put into their blocks.....what happens in this scenario?

They waste time mining until they get the newest block. This time lag, or rather, attempts to lessen it by not validating before mining on top of it, is what caused the last network split. Generally it's only a few seconds and 2 miners rarely find blocks at the same time. If they do, then the chain splits until one side finds the next block fastest, and everyone moves there and orphans the competing chain.

@Luke Mlsna please post answers as answers rather than comments :)

@LukeMlsna .... so, if a new block comes in, does a miner stop mining their current block? ....and start on a new block with new transactions?

Yes, they immediately drop what they are doing and start mining on top of the newest block. Because any time spent mining a stale block is wasted.

Not all blocks are mining the same transactions in their respective proofs-of-work. Each miner collects enough transactions via gossip until they reach the block size limit. Not all transactions will make it into a certain block, so those will be more likely candidates to make it into the next block. Miners decide which transactions to include in a block with the following equation:
priority = sum(input_value_in_base_units * input_age)/size_in_bytes


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Block chain receive payment api not working
I am building a little online app to accept bitcoin payments in my website. I have a blockchain.info wallet and I am following their Receive Payments Api, which can be visited here: http://blockchain.info/api/api_receive
The monetary part works great, but the HTTP Callback Notification does not take place and my online store is not notified of the payment. However, the TEST callback does work.
I think it is a problem on his application.
Has anyone implemented the "Receive Money API" successfully?
Is there any other alternative for received instant payment notifications? (To several different addresses)
A friend of mine reports the same issue. We need a little help :)


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How to restore wallet from wallet words after hard drive crash with no back up?
If I lost wallets on hard drive crash, how do I restore with just my wallet words? Restoring data from back up is not working

Since you added the Electrum tag to the question, I'll assume you're using Electrum.
When you first start up Electrum, you get the choice of creating a new seed or creating a wallet from an existing one. At that point you would select to enter your existing seed words, and it should recover your wallet.


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Why the leading zeros in the desired hash pattern?
Why are leading zeros desired in the block chain hash?  I have searched the internet but cannot find why.

The leading zeros are there to control the difficulty of the problem. More zeros mean a lower space of possible solutions and hence harder problems (more hashes to try before you find one that wins).

Thank you.  I wasn't sure if it had something to do with sequencing.  It makes sense that it's just to control the difficulty.  It's fascinating.

Why making it harder? Why it should be difficult to sign a block?


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What if same transaction is added in more than one block of different miners?
I know that miners have freedom to choose transactions from memory pool,
Let say there are 5 transactions Tx1 Tx2 Tx3 Tx4 and Tx5 in memory pool,
There are 3 miners M1 M2 and M3
M1 has created block with Tx1 Tx2 and Tx3
M2 has created block with Tx2 Tx3 and Tx4
M3 has created block with Tx2 and Tx5
==
M1 successfully solves the block and get reward in terms of bitcoin and transaction fee
at same time M2 and M3 successfully solves the block,
In this case, will M2 and M3 gets reward and transaction fee? as Tx2 was already part of M1's block which was already confirmed.

No, the blocks from M2 and M3 will most likely end up being discarded. The reason being that as soon as M1 broadcasts its block most miners will drop their current block and start trying to solve the next one.
There's nothing to stop M2 and M3 broadcasting their blocks after M1 in the hope that they will also be able to generate the next block and take over the longest chain. The problem is that these days the cost of generating a block is in the 10's of thousands of dollars in electricity so it's an expensive gamble to try and solve two blocks in a row.
And in answer to your main question if a transaction that's already included in a block appears in a subsequent block then the new block will be rejected as invalid by full nodes and other miners.

What will happen to Tx4 and Tx5 in this case ? as blocks by M2 and M3 are rejected.

"In this case, will M2 and M3 gets reward and transaction fee?" Simple answer -> Yes. But block rewards are not spendable right away. They are timelocked for 100 blocks.
When this happens other miners will imply which one of these 3 blocks(M1,M2,M3) they accept by exerting pow on top of it. Within a couple of blocks one the blockchains will outcompete the other two. The rewards in the block that is now in the longest chain will be spendable AND accepted by anyone that follows that chain once the 100 block limit is achieved.


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Why can't we make the Bitcoin software start the blockchain from the beginning?
I"m really wondering: you see 13 gigabytes (current blockchain size) is big enough only because there are all of transactions.
Can Bitcoin developers create such a piece of code which will shrink the size of the blockchain by collecting information of all addresses and representing some kind of inputs without using a Merkle tree, but in "database" style (like 4.5 bitcoins belongs to Alice, 2.3 belongs to Bob, ... ,.. .. and so on)
If blockchain size could be shrinked once in a year, then that would be a great solution.
Why isn't such a model allowable or what is the probability that Bitcoin developers will adopt this kind of protocol?
My solution here implies that everything on Bitcoin goes on the same way, but except for the fact that there will be a blockchain limit like 250 gigabytes for the blockchain - once the network will reach that limit, the network will agree on the last included block of transactions, after which the whole network will switch to a new blockchain file which won't wipe out everybody's bitcoins, but which will just create the genesis blocks based on previous files with all previous inputs belonging to their owner's addresses.
Please don't just say "it won't work".

And how exactly would the network agree on the last included block in order to spawn your new blockchain? That would be kind of complicated.
In my opinion Merkle tree is already fixing the problem. Downloading the headers of each block is enough to verify payments.
Remember that only miners actually need all of the blockchain data. Clients don't.

Pruning the whole Bitcoin ledger information is possible, and there are some alternative clients that use that, to reduce de current block chain a lot, but recreating a new block chain with only the unspent outputs is not that easy as it sounds as that would require regenerating all the hashes according to the difficulty at each time.
Even with the increasing hashing power (which is not guaranteed to continue that way) it will be an enormous task to recreate a pruned valid block chain. Also, there will be some problems with snapshot block hashes that are inside the client code.
If you go for another system that avoid creating a valid block chain, then I think that it is already possible for non-mining nodes. Some light clients will trust some kind of central server that has the full block chain. That way, you can get a reduced version or just delegate transacion verification to it.
If the client is modified that way for mining nodes having only one "trusted" server, it could be a solution, but then you have a centralized server and not a P2P.
So to get a fully decentralized system you need to be able to trust no one and thus having all the information on your own is the only way without reimplementing the whole protocol to create a new reduced blockchain that is safe and unique.

Individual clients could do this; if they select an (arbitrary) starting block, and calculate the location of all the bitcoins at that time, they could start off from there. They would be unable to see transactions that happened before this, of course, but they would know all the balances.
For example, as I write this, we are at block 286293; I could call this my "first" block (after verifying every transaction leading up to it), with a "starting block hash" of  0000000000000000258d8d361e9510df41e6da81751c98134083bf167088390 and make a list of all the balances so far. My software would be completely compatible with all other bitcoin software, except that it takes on faith that this is the starting block, and it would be unable to view prior transactions.
This does depend on there not being a fork (or, at least, not being on the wrong side of the fork) at the new starting block. For this reason, I would expect such a block chosen would not be the most recent block, but, say, one that is a few days old. You would, of course, be depending absolutely on the trustworthiness of the starting block.
Most software already does a variation of this to save having to process the entire blockchain for every transaction it sees.


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Saved .bitcoin directory full ~9 GB block data, won't work when copied to another system
I had to delete my .bitcoin directory in Ubuntu 12.10, after months of getting the near 9 GB of blk data files.
I copied everything over to another machine (and back to the original too) and it gives me:

A fatal error occurred. Bitcoin can no longer continue safely and will quit.

     EXCEPTION: St13runtime_error
     CDB() : can't open database file blkindex.dat, error 22
     bitcoin in Runaway exception

I tried chmod +w on the files, but still no go.

Two things come to mind as possible reasons.
The most probable reason is that you've switched client versions. There was a switch between 0.7 and 0.8 in how the block index (not the block data itself) was stored; it was changed from BerkeleyDB to LevelDB. If you remove the blkindex.dat (and really want to keep an index around, which is unlikely) you can restart the client with -rescan and -txindex. It will take a while (an hour?) to complete the indexing.
The other reason that I can think of is that it's genuinely corrupt, but that's unlikely.

No I used the same client version, bitcoinqt, each time. I tried this on the original system used for DL'ing all the block files. Which was ubuntu 12.04 LTS and another newer system Ubuntu 12.10. Both with the 0.7 bitcoin. I'm not familiar with running bitcoin from command line yet. Silly question but can you use (send , receive bitcoins , etc) without having to get all those massive block files? I could fine no answer to this anywhere else.

I deleted (moved to temp directory) the blkindex.dat file and then started ./bitcoind from command line with -rescan and -txindex options. It started running but it wiped out most of the blk0004.dat file and so wants to download yet another 2 gigs of data. Is this the only way?


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Is there a way to set up proof-of-work systems so they would be even more useful?
One of the arguments made against Bitcoin's design choices is that it wastes resources authenticating transactions. In particular, finding small hashes is completely useless for the world.
Are there approaches (or other crypto-currencies) that use proof-of-work by working on some useful difficult problem? There are plenty of projects like SETI@home or Folding@home that distribute difficult but potentially useful calculations among different users, is there a way to use such useful calculations for building a proof-of-work system in a crypto-currency, or is there a fundamental reason (economic or computational) that a proof-of-work must involve useless work?

This question is invalid; useless is arbitrary. What you are describing as useless is useful. The proof of work system in place allows for even distribution for bitcoins

@user9704 I set up a clear criteria for what I mean by useful work. I.e. work that provides utility outside of simple authenticating interactions.

@Serith I disagree with your change of title to this question. There are a few users who are offended by my use of the word 'useless' but I really use it in the setting of computation that is useless for things except bitcoin. It would be better to edit my question to make this clear instead of making the question itself suggest that the current proof-of-work system is performing a useful computation and not just wasting cycles in order to authenticate.

NooShare is such a proposal - http://www.reddit.com/r/Bitcoin/comments/pve08/btclike_cryptocurrency_with_arbitrary_tradeable/

@ripper234 : Please consider putting this answer as a response, with a bit more detail.
This is by far the best response, that answers correctly the question. It's a shame it is hidden in the comments.

@RaphaelJolivet - done. http://bitcoin.stackexchange.com/a/9395/78

Here is an example of it being set up: Hybrid Mining: Exploiting Blockchain’s Computational Power for Distributed Problem Solving

I think the premise of the question is not correct. The work is not useless, it secures the transactions. The public hash chain ensures that Bitcoins can only be spent once. The mechanism piles computations on top of legitimate transactions so that the recipient knows that an attacker would need at least as much computing ability to "undo" the transaction.
There is currently no known way to make the work more useful. The problem is that the primary purpose of securing transactions imposes a number of requirements on the work done:

The work must be much, much easier to verify than to do. So it pretty much has to consist of searching for something rare, doing billions of searches to test if an input has a particular characteristic. That way the verification simply requires confirming that the input you found has that characteristic.
The work must in fact secure the transactions and not be severable from them. If I see that you sent me 10 Bitcoins and then billions of computations are piled on top of that, it must not be possible to remove that transaction and then pile those same computations on top of a conflicting transaction. So you can't use the result of an arbitrary chunk of work to prove work on the Bitcoin chain.

It's hard to imagine any additional useful work that could be accomplished while still meeting these requirements.

I think question title is a bit misleading and should be change to "Is there a way to set up proof-of-work systems so it would be even more useful?"

How about finding prime numbers? That should at least fullfil criteria 1. I do not know how useful it is, though.

@David: How is finding prime numbers attached to Bitcoin transactions useful?

@DavidSchwartz I meant finding new prime numbers, which had previously not been discovered.

Finding prime numbers is the basis behind Primecoin. Finding primes is useful to some extent.

I'm not able to answer because I don't have enough reputation, but there's this paper on the topic: https://eprint.iacr.org/2017/203.pdf

NooShare is an idea for:

a decentralised ledger similar to Bitcoin with the novel feature that
  its proofs of work are iterations of essentially arbitrary
  Markov-Chain Monte-Carlo (MCMC) chains, the scheduling of which can be
  purchased using the currency itself. It is a novel economic basis for
  sharing fallow computational resources.

I don't know if it moved passed the initial design phase, but it's worth a read.

That does sound interesting, but are MCMC chains useful?

It looks like NooShare is insecure and never took off since I cannot find NooShare being used anywhere. NooShare was just an idea but it does not seem to have worked in practice.

The problem is that no one has come up with a proof-of-work system based on useful work that also:

Generates easily verifiable solutions
Can have the difficulty of finding a solution adjusted

For example, if the system were searching for prime numbers, the solutions would take a long time to verify as being prime.  The difficulty of finding the next prime also can't be controlled, it just continues increasing.

any NP-complete problem, by definition has an easy to verify solution. It is relatively easy to gradually increase the difficulty by increasing the input size. Further, useful NP-hard problem abound in science: say protein-folding, or circuit-layout optimization.

The problem with @Artem's suggestion is that you can pre-compute the solutions to a lot of problems. The blockchain makes block N+1 depend on block N, so it's impossible to calculate in advance.

@ripper234 my suggestion is definitely wrong, since otherwise it would be in use. However, the point of my comment was as a counterexample to what Chris suggested as an answer. However, people seem to like his answer. It would be nice if he explained how a general NP-hard problem does not qualify, though. As for my comment, it can be made to depend on previous blocks by making the input to the next problem to solve depend on the previous block (say there is a database of hard problem instances to solve, then hash of block N can be used to chose next problem to solve).

You would need as many problems as hashes. Otherwise, the proof of work doesn't actually prove work. (Someone can simply choose transactions to get the hash that selects the problem they already solved.) The proof of work must conclusively depend on at least the hash of the previous block and the transactions in it such that the proof of work is provably impractical to attach to any other work.

Assume for a second that we found a proof of work algorithm that had all of the good properties of sha256, but was also useful for SETI and maintaining world peace.
Now suppose a group of miners collectively have more than 51% of the hashing power. In which of the following scenarios are they more likely to collude to double spend via a 51% attack:
A) When the proof of work algorithm     is something like sha256 and is only useful for securing the bitcoin network
B) When the proof of work algorithm helps find aliens and maintain world peace in addition to securing the bitcoin network.
In Scenario B, if BTC lost all of its value due to a 51% attack/double spend,  miners' hardware would still be valuable because although it couldn't mine bitcoin, it could still find aliens and maintain world peace.
In Scenario A, if BTC were to lose its value, miners' hardware would go down with it, due to said hardware's uselessness for anything other than mining bitcoin.
In short, having a "useless" proof of work algorithm (where "useless" just means being able to secure the bitcoin network and nothing else) is a plus (for the bitcoin network,) because miners will be less tempted to trash bitcoin, knowing that their hardware would be worthless if they were to do so.

Interesting. I don't think it was part of the original concept. But interesting.

Some discussions around how to make it more useful
https://en.bitcoin.it/wiki/Intrinsic_worth_brainstorming
https://bitcointalk.org/index.php?topic=11834.0

"Merged Mining" (simultaneously mining on multiple block chains with the same amount of work)  may not be useful in a "real-world" sense, but at least it also produces Namecoins or Solidcoins or what have you in the process of producing Bitcoins.

No, because there is a significant advantage in requiring that the work be done on the actual transaction record, and not on any arbitrary problem.
By making the problem include the transaction record data, it makes any changes to the transaction history require providing a new solution, and this prevents a party from slowly 'storing' solutions, and releasing them all at once, since there are always new blocks of transactions being added to the block-chain, which means the required solution keeps changing, depending what the last block of transactions is.

Here's one approach:
Least action principle as an alternative proof of work system
Succinct Computational Integrity and Privacy Research (SCIPR) is possibly another area.

If you made the computation "useful" in some other sense, then in principle you could just sell that "useful" output, and thereby decrease the net economic expenditure securing the blockchain, making it less secured.  So bitcoin's "useless" computation is useful, whether or not it has another use.
I recently answered this question on my blog, more details can be found here: https://blog.sldx.com/is-bitcoins-proof-of-work-useless-work-a411480d3eb3

content at the url is no longer available.

How do you feel about those who have mined salt, or gold?  Salt/gold is useful outside of it being a source of liquidity (for flavoring food and keeping it from rotting, or making pretty things.)  But they don't secure a blockchain...

I thought I would give the answer I know to this question, and that is an economic one.
One of the reasons for using proof-of-work (apart from the technical usefulness) is as a way to inherently give the currency value. If the currency value is too high, to the point that it costs less to buy the computing power to counterfeit currency than it does to buy the currency directly, then there is an economic incentive to counterfeit and stabilize the price.
If we use a problem that is not useless, then there is a chance that it will be more useful to some that to others. As an example, solving an instance of problem X might generate income of $Y for person N, and no income for person M. (Say we are folding proteins and person N is a pharmaceutics company that can use this to build a new drug, while person M is a random person). Then, if it costs $K to counterfeit the currency by buying computing time, then for person N it would cost $(K - Y) while for person M it would cost $K. This could lead to a destabilization of the value of the currency.
Thus, if there is a useful problem, it must be equally useful to ALL users of the currency.

could someone comment on the downvotes? Is it because of self-answering or did I state something false in my answer?

I didn't downvote, but your answer doesn't seem quite right to me.  You can't actually counterfeit bitcoins.  However, if you control a majority of the network's processing power you can pull off a double-spend attack.  I'm not sure how this is connected to the cost of finding solutions though.  Do miners who don't have to pay for electricity have more incentive to attack the network than those who do have to pay?

Miners who don't have to pay for electricity are more likely to continue mining even if it's unprofitable when the cost of electricity is factored in. For this reason, mining is likely to tend to remain slightly unprofitable for all but those who need to convert electricity to heat anyway or have excess electricity they have no way to store.

@DavidSchwartz: How can miners don't have to pay for electricity? Are they stealing it?

@Hans-PeterStricker: many renewables produce energy regardless of demand. For instance South Africa invested heavily in hydro energy for a steel industry that didn't flourish. Wind energy isn't storable yet, so either turbines stop, which may cause problems, or the energy gets used for a heatsink or other dump - like Bitcoin mining. Energy use is a major criticism of Bitcoin, but the economics push for useless energy, not useful, & revenues can support renewables

Another excellent reason to select an algorithm that is not useful in any other context other than bitcoin alone is so that the infrastructure prepared for the purposes of securing bitcoin alone is only ever incentive-compatible with securing bitcoin.
Consider the recent introduction of numerous altcoins that share the same PoW algorithms, if the work that being done is meaningful in various contexts then miners will not be dedicated to securing bitcoin as there are economic considerations as to what the work should be spent to contribute to. For example, due to Bitcoin Cash and Bitcoin sharing the same SHA256d PoW algorithm, there's been greater volatility in hash-rate in both cryptocurrency which indirectly weakens security as some proportion of work has to be re-directed elsewhere and it also reduces usability experience to due greater variance in block inter-arrival times.

This post is old, but I got redirected here and read many comments.
Many arguments about why the algoritm shoulndt do nothing outside the system have a workarround.
Some say that the solution having an extrincic value could desestabilize the system because of usefull solutions having intrinsic value.
I mean houmans are specialized in tasks and grouped by their specialization, one group knows little about the other and then cross platform solutions scarse.
For a start, there's gold and it have uses so it also has intrinsic value, there's gold on our computers, our teeth and lots of stuff meant to be durable, it's not usefull as a car or a kilogram of potatoes though.
An equivalent of gold in calculations would be any problem that hasn't any direct application and possible will never have but it's still usefull for knowledge just to satisfy curiosity, there's lots of unapplied math problems of this kind I think and they're worthless because nobody would care about it, yet is a problem intresting for humans that got a solution.
Other thing to add is that computer power incresed since this post and bitcoin somehow operated to maintain value by adding difficulty, hence as far as I know (not very much), mantaining transactions is an easy problem now so an additional task of solving the hawkings radiation would be an added difficulty that I assure you has a f*** of economic value.
I can question myself is the real problem is economist knowing few of unpractical solutions outside they're self made system, and that there is a miracle that some hackers involved to create the bitcoin.


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BCH to BTC in same Trezor wallet
I changed BCH in my Trezor to BTC using the wallet coin splitting tool and sent it back again to the same wallet using a new BTC receive address rather than another external wallet like eg Electrum using Shapeshift exchange. But the BTC didn't arrive. Have I lost the coins or are they just lurking in cyberspace waiting to be found again ?

If you sent BCH to your Trezor BTC address or vice versa, you can use https://trezor.io/recover-coins/ to recover your coins.  The only exception is if you send BCH to a BTC 3... address (segwit), since these are not supported by Bitcoin Cash.
To convert BCH into BTC or vice versa you need to use an exchange.

You can't convert BCH to BTC using the splitting too. You can only claim  BCH that you got as a result of owning BTC when Bitcoin Cash forked. So, after splitting, what you end up with is new Bitcoin Cash, not new Bitcoin.
If you sent that BCH to a BTC address, what you actually did was send Bitcoin Cash (not Bitcoin). This situation is already covered by joho's answer.

Double check your addresses as it is very easy to mix them up when dealing with splitting then Shapeshifting. You can check your transactions and wallet balances on the respective blockchains such as Blockchain.info for BTC and Blockdozer.com for BCH. In other words, you still may have both BTC and BCH as the transfers might not have transpired.


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My balance says 100. mBTC. How many bitcoins is this, and what is the value in British pounds?
Cant find an easy answer anywhere? I would like to know what this means and the value etc

Is it 0.100 bitcoin or 0.0100 bitcoin?

without specifying the software you used, I guess it is Bitcoin Core client. Then the "m" identifies "milli", or 1/thousands of a Bitcoin. Today Bitcoin comes with 8 digits after the point. So you could have 0.001 Bitcoins x 100 = 0.1 Bitcoin. And now what can it be in Pounds - you may want to look this up in coinmarketcap.com, I think the BTC is ~ 5400. So you would have 540 pounds. Please double check this, an then you might provide your own answer here.

mBTC stands for the SI unit Millibit which is 1 thousandth of a bitcoin, or 0.001. So you have 100 mBTC * 0.001 BTC, or 0.1 BTC. The price of 1 BTC at the time of this writing on Coinbase in GBP is £5,485.21 to 1 BTC. Your 100 mBTC would then be valued around £548.

No problemo. Please consider marking this as the Answer so the question doesn't still look un-answered.


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How does changing transaction data in a block change the hash of previous block?
I am reading this article, within which it mentions that
"Imagine this for a second, a hacker attacks block 3 and tries to change the data. Because of the properties of hash functions, a slight change in data will change the hash drastically. This means that any slight changes made in block 3, will change the hash which is stored in block 2, now that in turn will change the data and the hash of block 2 which will result in changes in block 1 and so on and so forth."
And I do not understand if a hacker attacks block 3 and try to edit the transaction data within it, how would this affect the hash stored in block 2? And hash of what is stored in block 2 ?
Can someone kindly clarify for me please ? I am just getting confused.

The author of article is wrong. Try to read more authoritative sources

Can you kindly point me to some authoritative sources please ?

It does not!
Next block contains a reference to previous block header hash.
Let's say the blocks are ordered as 1<-2<-3<-4<-5<- with block 1 being the first block in the chain (so called genesis block).
Block 2 header contains a reference to block 1 header hash.
Block 3 header contains a reference to block 2 header hash.
Block 4 header contains a reference to block 3 header hash, and so on.
If someone changes block 3 header block 4 will not point to that block's header any more, and the part of the chain -4<-5<-6<-... will be invalid.
Each block's header contains a construct (called Merkle root) which is derived from all transactions. Thus changing a transaction in block 3 will make Merkle root in the header of block 3 invalid and the attacker must also change that. Meaning the header will change and thus block 3 header's hash will change. Thus block 4 header won't point to block 3 header hash any more.
NOTE: On the other hand block 3 will also be invalid with respect to its required target threshold but this is another issue.

Imagine this for a second, a hacker attacks block 3 and tries to change the data. Because of the properties of hash functions, a slight change in data will change the hash drastically. This means that any slight changes made in block 3, will change the hash which is stored in block 2, now that in turn will change the data and the hash of block 2 which will result in changes in block 1 and so on and so forth.

In the statement that you have quoted, block three is the oldest block. It has been first buried under block two and, then block one.


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How can i double spend from my unconfirmed transaction for more than 5 days
I deposited 0.042105059 BTC from my bitcoin account (1KDcKTBTLWnLUED6yMA4Huj5CfzgKfuvJF) to Livecoin.net account.
(1DaHJ3ewQ3XBDxTLFQ4U9E9C4z8w9uEvGW) about 5 days ago but it is still unconfirmed in blockcain.
The transaction has 0/3 confirmations in blockchain and still pending.
https://blockchain.info/tx/4e19db9b29df ... 756396858c
I learned that it because of lower fee. How can cancel or double my coins.
Could any miner here push my transaction for me.

Which wallet are you using? The bitcoin-core wallet has a couple of options to either zap mempool transactions or increase the fee on an existing transaction.

Bitcoin wallet from blockchain

How can i increase the fee on the existing transaction?

I'm not familiar with that wallet. On the Bitcoin core wallet you can right click a transaction and choose "Increase transaction fee". To do that the transaction must have had the "Replace by fee" checkbox ticked when it was created.

You mean you are familiar with Blockchain.info bitcoin wallet. please help me with how to double spend my bitcoin in blockchain.

I'm not familiar with it, sorry.

1. You could try child-pays-for-parent.
Your unconfirmed transaction with the txid 4e19db9b29dffd508073dd5d67ad8096559e28ef92da0eeb28fe85756396858c has two ouputs.
I guess 1CfSS3Q6UxCinGg82gzwm1M6LfaxUFUJh8 (value 0.05739491) is your change output...
You can use that change output as an input for a new transaction where you pay a high fee. Miners will then be interested to mine that new transaction but they can only if they also mine the old one (txid above).
You may use 2x the recommended
2. Double-Spend (harder)

Use -zapwallettxes=1 as Bitcoin Core startup argument.
Use CoinControl (enable it via Bitcoin-Qt settings)
Select your "blocked" input (1KDcKTBTLWnLUED6yMA4Huj5CfzgKfuvJF from 7aa1366669c3c836d7bf7abbc9b934af62bf669a250b66ccd2d72197aeafee35 0.0995BTC) in CoinControl and do a new transaction

Please show me steps to go about the child-pays-for parent.I try the this process how to execute the double-spend operation that @FlyButterfly described: https://bitzuma.com/posts/how-to-clear- ... ansaction/ but the last process says "64: scriptsig-not-pushonly". what does it mean?

zapwallettxes has been removed


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X11 | multiplier & maxDiff number to multiple the shares by in order to display hashrate
What is the correct formula for X11 to calculate hashrate?

right maxDiff number to multiple the shares by in order to display
  hashrate

We need hashrate multiplier and the maxdiff
Example:
scrypt: 2^16

sha256d: 2^32

maxDiff with:
scrypt: 0x0000ffff00000000000000000000000000000000000000000000000000000000,
sha256d: 0x00000000ffff0000000000000000000000000000000000000000000000000000

diff1 for X11 is
0x00000000ffff0000000000000000000000000000000000000000000000000000


text:
How to redeem a private key in case it is compromised
I know MtGox allows me to redeem a private key, but that doesn't necessarily ensure that all the value is extracted from that address in a timely manner. Is there no simple way to send the entire value of a private key to another address in case you believe the private key has been compromised? My real use for this is in having offline/paper wallets. I would like to transfer my bitcoins to an offline "savings" address, then when I want to make a withdrawal, be able to transfer the entire value of that private key to a new address because, having entered the private key somewhere to redeem its value, its privacy could have been compromised.
This seems like a very common use case for paper wallets. Am I missing something? It should be easier to spend the value from a particular address. Why can't I use my bitcoin client to spend a specific address? I can import private keys into bitcoin v0.7.1-beta (although even that is an obscure debug window) function, but it looks like sending from a specific address is also an obscure debug function (sendfrom). Why is this so obscure when it seems like such a common case? What is one to do if they suspect a particular address' private key of being compromised?
Also, how can I tell how much value is available on my various addresses to make sure I extract the full value? Blockchain.info seems to do a good job, but it's Dutch -- isn't there an English site or bitcoin client function to determine an address' value. That too seems really basic. I have tried blockexplorer.com, but that site rarely seems to work.
I feel like I'm trying to accomplish the most basic of tasks, and the tools just aren't there, so I must be missing something.
P.S. I am using also Android devices with BitcoinSpinner. I would be interested to know if some more sophisticated clients allow this more easily -- scanning both a private key as a source and a public key as a destination -- to create a transaction.
P.P.S I'm also not clear on how to use the backup provided by BitcoinSpinner. I tried to import it as a private key into bitcoin v0.7.1-beta on my desktop, but it didn't work. The only way I could figure out how to essentially get a backup of BitcounSpinner into my desktop's client was to import the private key, which I know is wrong. There must be some way that backups are supposed to work.

I believe a suggestion from ripper234 in discussion is the answer I'm looking for - use the Armory client instead. I found this page about Armory particularly reassuring and will be trying that client shortly: http://bitcoinarmory.com/index.php/using-offline-wallets-in-armory
Edit: I see now with the help of the Armory client that the name of the feature I was after is a private key "sweep". Apparently it's common enough to have its own name and menu item in Armory. That will "sweep" the value out of the provided address into your Armory wallet to make sure that anyone else who may come into possession of the private key won't have access to the value it stored.

If you want to redeem all funds from a private key and never use it again - you can for example create a new wallet file, run a bitcoin client, import the private key, let the client fully synchronise, and then send all your available funds to another address you own. After that, you can move your old wallet back where it belongs and use the new funds transferred. The redeemed key will not interfere with your normal wallet and you will have your funds.

This involves under-cutting the normal function of the bitcoin client by 1) renaming its (obscurely located) data files, and 2) using "debug" functionality to import a private key. Doesn't it seem odd to have to go to such lengths simply to send a transaction from a specified address given its private key? Also, wouldn't it be simpler to import the private key and then use sendfrom to send from the specific address? Simpler, but still not simple enough, IMO (because sendfrom, like importprivkey is a debug function).

@BlueMonkMN - people don't usually work with private keys, but rather with addresses. What you're doing isn't "a basic task" - I've been using Bitcoin for 1.5 years and have never had the need to do what you're trying to do.

@ripper234 OK, so how do you (or how should one) keep offline backups of bitcoins should your electronic copies fail? Even USB drives seem somewhat less reliable than paper in some ways.

@BlueMonkMN - encrypt with a strong password & upload to dropbox. Only ever decrypt on a dedicated secured computer.

See also https://en.bitcoin.it/wiki/Securing_your_wallet

@ripper234 I said offline. Dropbox is not offline. Let me put the question this way. There are paper bitcoins out there. How do you spend them? (See paper wallets at http://bitaddress.org/ where you can create your own paper bitcoins/wallets.)

let us continue this discussion in chat

These days I use Android Mycelium Wallet. If you go to the Accounts page, and add an account, scrolling to the bottom, there's an "Advanced" button to scan/add a private key, which I believe also does what I was trying to do here.

From a mobile or tablet access EasyWallet.org and click Scan.  Done.


text:
How do I use my Bitcoin-Qt wallet address on Blockchain.info?
My Bitcoin-Qt client is still synchronizing with the network. I'm unsure of how to use my Bitcoin-Qt wallet address on Blockchain.info. I've put my address on Blockchain.info as (watch only), but how do I get full access to my wallet on Blockchain.info?
I do have a passphrase and the wallet is locked. Does Bitcoin-Qt need to be fully synchronized with the network for me to be able to access my wallet?

The block chain can take a (very) long time to synchronize with.. patience, anon.

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

You have to unlock your wallet, export the private key for your address and then import it to Blockchain.info. You don't even need Bitcoin-Qt then, because they store your privkey and your money!

Export the private key for a specific Bitcoin address from Bitcoin-Qt.  Copy the value to your clipboard.
Import it
into Blockchain.info wallet (log into your Blockchain.info wallet,
click Import/Export tab, for the Import Private Key field paste the
private key.)


text:
What is a hallmark node in NXT (nxtcoin)?
What is the purpose of a hallmark node for NXT?

From the NXT wiki

A hallmark is a "stamp of approval" for a Nxt node.  By creating a digital signature based on your IP address and secret passphrase (private key), you are verifying that your account "owns" a node and is accountable for it.  This helps protect the network from attack, and increases the network's trust in your node. You do not need to generate a hallmark if you are a casual Nxt user.  It is a very good idea for those who operate public Nxt nodes on dedicated, public servers. Hallmarks have no impact on forging.


text:
When does freebitco.in cash out?
I found a web site where you can win bitcoins, freebitco.in. How do they work? Do they use JavaScript to mine for bitcoins on your client?
And when do you get the mBTC you win there?

According to the website, if you click on "Auto Withdraw Enabled", you see:
"Payments are automatically sent every Monday to all accounts with a balance greater than 0.00005460 BTC".
For example, yesterday I received my most recent payment around 1 AM on Tuesday EST.  They send the BTC with a note saying:

They state that it can take a while to get the payment approved.  From my experience with the site, I find they are pretty reliable.  They basically only check to make sure you didn't try to cheat somehow with referral exploitation or programs trying to modify the gambling feature they have.


text:
How do I go about installing a Bitcoin daemon in CentOS Linux?
I am trying to setup a Drupal e-commerce solution with a payment gateway of accepting Bitcoins during checkout, but I need a bitcoin daemon installed. How do I go about installing the Bitcoin daemon in my CentOS installation?
Is there a step-by-step guide on what I need to type to install this? It would be great if it can be installed via a package manager in CentOS. apt-get doesn't seem to work for me.

You'll want to find a yum repository that has bitcoind in it, as CentOS uses YUM and not APT.

If you would like to build from source: http://bitcoin.stackexchange.com/a/30106/19021

I host two bitcoind RPMs (i686, x86_64) on my website which will most likely work fine for you, as they're built for CentOS 6.4. Run this command to install bitcoind :
rpm -ivh http://tvdw.eu/bitcoin-0.8.1-1.el6.`uname -m`.rpm

If you want to download them manually, the files are:
i686:   http://tvdw.eu/bitcoin-0.8.1-1.el6.i686.rpm
MD5:    5be52618594a3eaded19052197c2f6ed

x86_64: http://tvdw.eu/bitcoin-0.8.1-1.el6.x86_64.rpm
MD5:    49ba4acbf9744e96bf12342888bc347a

The packages are unsigned, so install these at your own risk (aka: some level of trust is required here).
[Edit] This is the bitcoin.spec file I use to build these packages :
Name:           bitcoin
Version:        0.8.1
Release:        1%{?dist}
Summary:        bitcoin

License:        GPL
URL:            http://bitcoin.org
Source0:        http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-%{version}/bitcoin-%{version}-linux.tar.gz

%description
bitcoin

%package qt
Summary:        bitcoin-qt
%description qt
bitcoin-qt

%prep
%setup -q -n bitcoin-%{version}-linux

%build

%install
mkdir -p %{buildroot}%{_bindir}
%ifarch x86_64
cp -R bin/64/* %{buildroot}%{_bindir}
%endif
%ifarch i686
cp -R bin/32/* %{buildroot}%{_bindir}
%endif

%clean
rm -rf %{buildroot}

%files
%doc README COPYING
/usr/bin/bitcoind

%files qt
/usr/bin/bitcoin-qt

%changelog

There's no actual compilation involved, it just puts the files in the right locations and wraps it in a nice little RPM.

there is no way to install the same ones from the main bitcoin site? Yes a level of trust is indeed needed. but for the sake of the paranoid user, how can one do it themselves.

@duckx I updated my answer with the bitcoin.spec file I use to build the packages.

You can also try this setup, by another fellow StackExchange member.
Or you might want to take the easier route and use a Bitcoin Payment Gateway.

Don't trust just any source. People smarter than me strongly recommend using the official builds from bitcoincore.org. On CentOS, I've had success using the official snap package, and I've copied the instructions below:
yum -y install epel-release
yum -y install snapd
systemctl enable --now snapd.socket
ln -s /var/lib/snapd/snap /snap
snap install bitcoin-core

PS: Use bitcoin-core.cli and bitcoin-core.deamon as commands.
PPS: You might need to run these commands as a super user (e.g. using sudo).


text:
I am going to buy bitcoins for the first time from a seller on LocalBitcoins. Please guide me.
I am going to buy bitcoins for the first time from a seller on LocalBitcoins. He says that funds can be transferred via internet banking. He seems to have good feedback, 9+ reviews but I am kind of nervous. What exact steps should be followed for a smooth transaction?
My plan is:

Send him my wallet address, and then wait for him to transfer the bitcoins.
Upon successful transaction, I send him the required amount through an online bank transaction.
??
Profit

I hope I am doing this right. Please advise.

so, you receive bitcoins first?!

local means local, i.e. hard money changes hands live... if you are going to use banking anyway, you can  just use Mt. Gox...

If he has a reputation and you don't, of course he won't send first. Either you send first, you meet or you use escrow.

@Lohoris: Using Mtgox has several issues, the $50 fee for international wire being one of them. A local bank transfer is completely different.

Related question: How do I buy Bitcoins safely face-to-face

Meet him at a public place and do the exchange using a phone bitcoin-app and cash. Make sure that his reputation is worth more than a possible robbery/scam.

LocalBitcoins use escrow, so you will be safe.

You could improve the answer by adding some more detail. Is escrow always enabled? How does it work?


text:
Anonymity versus trust
Bitcoiners seem to love to talk about anonymity. But to me, anonymous transactions are far from Bitcoin's greatest strength. And to some, the need for high anonymity is the first sign that someone is "up to no good".
But what happens if you need to the opposite? I find myself in a situation where I had listed a bitcoin donation address on my website, but someone was able to deface my website and put another adress in instead.
Now, of course this is a special situation, and since I don't know my adress by heart, it went on for a bit before I noticed this.
What got my mind buzzing was when I put my real adress back up, and a person asked me "How can I be sure this is really your wallet?"
The question is, how can I prove that I am on the other side of the bitcoin address on my public website? Sending screenshots is a bit impractical, and honestly doesn't really tell me much. Is there a way to do some kind of handshake with the recipient or in any way verify the identity of a bitcoin address?
I know this is directly against the core principles of anonymity, but a currency will still need trust for commerce to flourish, and I am curious if there is any method one could use.
Right now, I'm juggling the idea that the user sends a microtransaction with a 6 digit code, and the recipient tells the sender the code when it appears in my wallet. This is inspired by mobile bluetooth trust syncs. But there must be an easier way. I imagine a very high level of ingenuity among the Bitcoin community, any ideas what could solve this?
If your idea is based on "theoretical software" (something that could be made, but simply hasn't) I'm willing to hear you out as well.

If you have a secure channel to the recipient or some way to identify communications as coming from the recipient, just have them send their Bitcoin address. If you have no such channel or method, it's obviously impossible. What can you do to prove your address is yours that I can't do to prove my address is yours?

Identity verification on the internet is a difficult problem. One of the relatively common techniques in use is the use of the PGP web of trust. You create a unique PGP key and have other people sign it, indicating that they have checked your identity. Once you are connected to enough people, it is possible to verify with some degree of certainty that your key indeed belongs to you. If you then post a PGP signed message containing your Bitcoin address, the signature can be verified, and the identity of the key can be checked via the web of trust.
The limitations of this approach are:

Most people won't be checking the signature
Most people don't use PGP/GPG and thus are not part of the PGP web of trust and therefore will not be able to verify your key identity even if they can check the signature.

SSL is a common method to verify a website's identity - however if the site is defaced via a hack, that will not help one bit.
Basically, this is not a problem of anonymity of Bitcoin, but a problem of how to prove your identity in the context of digital communications. Consider, that if you had a PayPal address on your site, the hacker could have changed your PayPal address to one controlled by him, just as well. There's nothing special about bitcoin here.

An alternative is that the person will create a new address only for the donation amount, transfer the amount to it and then send the new address to you. Then is up to you to merge than amount into your real, undisclosed address.
In this way you avoid giving people and address that might be tampered with. Assuming of course that your email is harder to tamper with than your website.
On the other hand, this is added complexity for the donor. Maybe this could be implemented on top of bitcoin client (send coins to new address)
Edit lets take this idea a bit further. Or actually lets take a step back. Let's think in normal cash. Cash comes in several denominations; 10 - 100 - 1000. If you think of it, you can transfer bitcoins not only by a transaction from address to address (which is the way that was envisioned in its inception), but also, transferring by ordinary means (i.e: email) an address with the transaction amount works just as good. Both parts can agree that the transaction is completed after the receiver transfer the amount from the received address into a new address that the sender does not know.
I'm thinking that if some higher level library on top of bitcoin would implement transfers between parties not as transactions between two addresses, but as many transfers of addresses with small amounts in each of them, from an old address that is known to both parties to new addresses that are only known to the receiver. I think that in this way, most of the statistical analysis you could do to identify real identities behind might be a lot harder

To start with, you could try using a vanity generator and getting a custom address that would be harder to forge (the longer the non-random string the better). You can also try memorizing last character of two of your address, just as a safety check.
You could also use a custom-made QR code with for example a photo you never folly posted on the Internet. If someone would try messing with that, you have a higher chance of noticing it right away.
I suppose in the future one could develop a trusted website for sending Bitcoins to a specific person by using their email instead of Bitcoin address, or providing a third-party service that links a certain Bitcoin address to you. These, however, are not available currently (at least to my knowledge).


text:
Send bitcoins using just a pub and private key
If I install the bitcoin command line client for linux, can I use just a public and private key to send coins from an address? I don't want to add it to my wallet file, I just want to move coins out of an address.

Update: After reading some of the answers I realize that I should have been more clear about my purposes. This is for more of a computer controlled money system. I want to be able to create addresses, and move money between them, and be able to move money out of addresses to other public addresses. I wanted it to be super light weight and not have to download the whole block-chain to achieve anything, and I don't want it to use wallets because they don't conform very well to what I am doing.
I want to be able to be given a private key and public address of a source, and a public address of a destination, to be able to send coins from one to another, and do it by just sending a message to the network. I want to be able to do it with only 10-20 MB of storage, and be able to do it by only connecting to a few nodes. Confirmations & balances will just be handled by hitting up some public resource like blockchain explorer.
Note: if it is not possible to do without the blockchain handy, then that can be accommodated for (though it throws in the need for a server for me rather than being purely client based.).

If you can code in Java, you can do this with Bitcoinj. See this question: http://bitcoin.stackexchange.com/questions/7708/how-do-i-create-an-offline-transaction-in-java-to-broadcast-via-blockchain-info

EDIT: I recalled that Wiki: Sweepprivkey proposal, is actually exactly what you are asking for, bitcointalk.org: Proposed RPC command: sweepprivkey. The latest news about the work in progress from jarpiain, dated October 15.

This is functional in the sense that I tested it succesfully on the
  real block chain. It's not yet robust enough for serious use. In
  particular, there are race conditions for accessing addrblock.dat.
I'm going to implement some of the sweepprivkey options and copy the
  transaction fee logic from CWallet::CreateTransaction() this weekend
  (I think it's best to keep the fee setting in one place, the -paytxfee
  option).

MtGox has the option to fund account with private key, and it understands several different formats, not only the standart one, e.g. it accepts mini format used by Casascius physical coins, MtGox adds redeemer for private keys including Casascius Physical Bitcoins
But if you want to send the transaction from your own computer then you need a software that would create a proper transaction using the public and private key, bitcoin or bitcoind can't do that without importing keys into wallet first, importing could be done with Pywallet or hopefully soon-to-be-official wallet export/import bitcoin patch, but make sure to backup your wallet first.

You can create a new wallet that has just the one keypair you need, move the coins, and then restore your old wallet file.

hm, your answer made me speculate that the purpose of this question is to move stolen coins without leaving too much footprint, but of course that's just speculation.

It could also be that someone wants to get rid of their old address that someone associated with their identity while keeping the coins in their new address.

This API will push your transaction into the network if you have your $priv_key
https://blockchain.info/merchant/$priv_key/payment?to=$recipient_address&amount=$amount_satoshi&fee=50000
But in order to inject this transaction onto the network for you, they require a minimum fee of 50000 Satoshi (0.0005 BTC) whether you specify a fee or not. For more details, see:
https://blockchain.info/api/api_send
But that fee (about $0.30) might seem a little too generous. Does anyone know of a way to do this for a smaller fee?


text:
Sent Bitcoin cash to Bitcoin wallet
I made transfer by accident from my bitcash to my bitcoin address instead of bitcash to bitcash, and it's up in the cloud but I cannot claim it. I sent bitcash coins from CEX.IO wallet to my bitcoin account in Trezor.
The transaction went thru and now it's in a cloud on my account but because my account is bitcoin its not possible to get bitcash.
Does anyone know how I can release the money?

Possible duplicate of What would happen if you send Bitcoin (BTC) to a Bitcoin Cash (BCC) address?

What it the first symbol of destination address? Is it "1" or "3"?

@MaxVernon: Nope, it's the other way around, and since BTC has since activated segwit, there's a significant difference.


text:
How to recover my Copay wallet using the 12 word seed phrase
I'm new to Bitcoin/Copay. I decided to signup at coinbase deposited $80. I read you needed a wallet. I decided on copay. Transferred the funds to my wallet. Everything processed smoothly and my copay wallet showed $76. I then went to the merchant and tried to pay. A spend password popped up. i couldn't remember the password. I may have mixed it up with my coinbase password instead.
I then did a little digging online and read that I could delete copay from my Android phone and reinstall it using the 12 word phrase to by pass/reset spending password. I did that. Now if I restore using only the phrase it creates a "Personal Wallet" with no funds in it.
If I try and restore wallet with 12 word phrase and try and guess the recovery phrase password (Under Advanced Options) I get an error saying
"Could not access the wallet at the server
Please Check
The password of the recovery phrase (if Set)
The derivation path
The wallet service URL
Is there any way I can recover my wallet/funds I do know the 12 word phrase. and I thought that would have all I would have needed.
Thanks for any help fixing this.

what is your wallet address for both?

Copay wallet Address is/was  1DcuwtWQ66FV39AJNcY6SpvbiMoVqWdoer

the good news you didn't lose your funds, they're still in your wallet/address

Well they are there but I consider it lost because I can't seem to recover them.

You may find https://metasafe.org useful

Could you figure out. I have the same issue. I have the 12 word, but can not recover / import.

Are you using the Import option when you try to recover the wallet?
This issue looks similar to what you're experiencing: https://github.com/bitpay/copay/issues/7399

I have tried create, import, recovery etc.In Copay, Bitpay and Electrum

According to several blockchain explorer websites your address 1DcuwtWQ66FV39AJNcY6SpvbiMoVqWdoer still contains 0.00621076 BTC worth today about $40 or half what you bought it for.
There was a single transaction:
Date              25-Jan-2018, 01:14:33
Transaction ID    b5e7252c40a92447960b64d336b05dc1a7334fe06371eeb6eabacaec5ce1 0a00
Confirmations     30888
Inputs #          1
Outputs #         2
Amount            +0.00621076 btc
Fees              0.00052679 btc
Fees per byte     233.09 Satoshi
Size (kB)         0.226

That transaction would be a transfer from Coinbase to your wallet.
So if you import your twelve word recovery-phrase (seed phrase) into a new wallet, you should be able to see an address "1DcuwtWQ66FV39AJNcY6SpvbiMoVqWdoer" in it.
If so, after the wallet has synchronised with the bitcoin network you will see the correct balance. A new full-node wallet may take weeks to synchronise. A web wallet or SPV wallet will be quicker (but web wallets are arguably less secure).

You shouldn't use the passphrase with their digits and dashes! // 1- banana 2- sugar// !
And also there is a second password may be used before,  while setting the strog security of your wallet,  please see that!

I think coinbase cannot not recover it for you but you can ask them.
The paraphrase you copied might be incorrect.
As long as you save all the required informations then there should be a way to recover it.

I can't see how the 12 word seed is wrong.  When setting up copay for the first time on my Android phone, I typed the words in note pad immediately. The next step in the set up process asks me to select the 12 words in the order it was giving. I selected the 12 words in order by what was I typed in notepad, and completed the setup. I checked each word for spelling by comparing them to the word list. Each is spelled correctly and one space between them.

hmm... when i used the vault, i remember ill give u a private key which u can use instead of the passphrase but it might updated so my answer may be inaccurate because i havnt use coinbase vault for long time

I used coinbase to send the funds to my copay wallet. The copay wallet is the one I'm trying to recover. I only used coinbase to buy the bitcoins and then sent it to my copay wallet.

You contacted them?

No I haven't. I assumed by what I have read that once it leave and goes to my copay wallet that there would be no way for them to reverse it.

I will contact them and see if they can.

If they can't then maybe u will loose the coins.


text:
How to make totally secure Bitcoin transactions?
So, I'm wondering if my system of protecting my bitcoin is totally secure.
If I have an old laptop, and I boot into tails linux from a flash drive, and download electrum on there, and only ever connect to the internet at my home WiFi, and only ever visit Coinbase (GDAX) and Gmail, are their opportunities to steal my bitcoin?
Is there hardware risk? Would I need to wipe the drive completely, or can I purchase a hardware wallet that transacts without connecting to a laptop?
Is there WiFi risk, or are Electrum, Coinbase, and Gmail all encrypted connections so it wouldn't even matter if there were a man in the middle? (am I confusing things here?)
Is there risk with Electrum? Should I download the core Bitcoin client instead?
Obviously no cameras or microphones in the room when you use the dedicated laptop, right?

Nothing is ever totally secure.

The primary concern with Bitcoin security is where your private keys are stored.
In your scenario the private keys are stored on a Linux laptop which is not unreasonable if you follow good internet hygiene and security practices.
The next best approach is to purchase a hardware wallet from the likes of Trezor or Ledger. These wallets have High Security Module (HSM) chips inside them that are highly resistant to being compromised. By highly resistant it means the private keys are stored on a tamper-proof chip and NEVER leave it. The HSM chip in the Ledger Blue is ST31. Google for ways to compromise the ST31 versus ways to compromise Linux and you'll get the idea.
With a hardware wallet it works in conjunction with a client on your PC but the crucial factor is the transaction (tx) is signed in the HSM chip and the only thing an attacker could do is try and replace the Bitcoin address in your tx. Most hardware wallets safeguard against this by displaying the recipient address on the screen when requesting verification of the signature operation.
And finally you could write your private key down on a piece of paper and hand-sign all your Bitcoin tx's. No electronic compromises to worry about.

If your machine connects to the internet at all, it should be considered potentially compromised.  Consider what happens to it if you visit GMail, which happens to deliver an ad with compromised JavaScript, for instance.
Secure storage of a bitcoin wallet can only be really considered "mostly secure" if the machine is never connected to any network, and only you have physical access to it.  Make sure all connectivity to the machine is disabled, such as USB, serial ports, WiFi, etc.
Sending a transaction over the bitcoin network for an offline, or cold wallet, consists of generating the transaction offline, then manually copying the transaction's hex representation to a node that is connected, and having it broadcast the transaction.  That is essentially what the Trezor and Ledger hardware wallets do - they generate the transaction internally in such a way that your private key never leaves the confines of the hardware wallet.  It then sends only the resulting transaction details to the bitcoin network, with the signature including your public key which proves you signed it with the corresponding private key.
Search "bitcoin cold storage" if you want to go down the rabbit hole.

Nobody else has made much of a mention of physical security, yet. You may also like to consider the possibility of:

Fire; do you have another copy of your private keys if your building burns down? Of course, storing additional copies adds additional risk of compromise.
Natural disasters; depending on location, you may also need to consider the possibility of flood, tsunami, tornado, volcano. Also consider unnatural disasters such as war.
Theft while unattended; if someone knew you had cryptocurrency of substantial value, might they just steal your computer hardware and read the contents of the hard disk? Is your password on a sticky note under your keyboard? (or on your monitor!)
Theft while attended; ie if a thief held a gun to your head...
Hardware failure; storage media gets corrupted sometimes, or just stops working.
Advising next-of-kin how to access the funds, without compromising them in the meantime.
Getting out of sync; if your backup copy is missing some of the most recent private keys, they are at risk. Using a deterministic wallet helps solve this one.

I know this isn't a complete answer, but each case will depend on individual circumstances and this may still be useful.

Look into the Glacier Protocol, which is a very expensive but extremely secure (although nothing is ever 100% secure) solution.

Nothing is totally secure.
That being said, the scenario you just proposed is "damn well secure" (whatever that means. This is just an opinion). Malware and hackers do not target those scenarios usually, they go for easier ones.
It depends on how much money you're planning on having in your wallet. That's safe enough for a couple thousand, but probably not enough for 100k+. Again, this is totally opinion-based.