Bitcoin Forum

I have lost a flash drive that contains my wallet.dat file.  What do I need to do to keep my wallet secure?  Is creating another address and transfering my coins to the new address sufficient, or do I need to take other or additional steps?  Thank you.

Yes, create another address and send your coins there. Backup your wallet.dat again or write down your private keys.

This is horrible advice.  Do you want sap33 to lose their bitcoins for some reason?

sap33,

Before your question can be answered accurately there are 2 pieces of information that are important:

What bitcoin wallet are you using that was lost?

• Bitcoin Core
• Bitcoin-Qt
• Armory
• Electrum
• MultiBit
• blockchain.info
• something else (if so, what?)

Is the backup protected by a strong passphrase?

Assuming that the answer to the first question is "Bitcoin Core", and the answer to the second question is "No", then you need to create a new wallet.  The lost wallet already has access to the next address that you'll create in the current wallet (and the address after that, and the address after that, etc...)

You should immediately create a backup of your current wallet.

(note: this process will require you to keep track of two separate files both named "wallet.dat".  Be VERY CAREFUL not to get them mixed up, and not to accidentally overwrite one file with the other.)

If you are certain that you have a good backup of the current wallet, then shut down the wallet (wait for it to completely shut down, which may take a few minutes).  Next find the folder where your software stores the wallet currently in use.  In Windows this is typically the %APPDATA% folder.  See here: https://en.bitcoin.it/wiki/Data_directory

Delete the wallet.dat from that folder (but only if you are absolutely certain that you have a good backup safely stored elsewhere).

Start your wallet back up.

You'll see the balance says 0 bitcoins and none of the addresses that you've used in the past are in the wallet.  Set a strong passphrase on this wallet.

Generate and store a new address from this wallet (write it down, print it, copy and paste it into a document, it doesn't matter how, but you'll need access to the address when the wallet isn't running).

Now make sure you create a good backup of this new wallet and store it somewhere safe.

If you are certain that you have a good backup of the new wallet, then shut down the wallet (wait for it to completely shut down, which may take a few minutes).  Next go back to the folder where your software stores the wallet currently in use.

Replace the wallet.dat in this directory with the backup you have of your original lost wallet (but only if you are absolutely certain that you have a good backup of the new wallet safely stored elsewhere).

Start your wallet back up.

You'll now see that your original balance is back, along with your transaction history and all the addresses from your old wallet.

Create a transaction sending your entire balance to the address that you stored from the new wallet.  This is why you needed to store a copy of it.  At this point you have access to the old wallet, and not the new one.  Wait for this transaction to receive at least 1 confirmation.

Shut down the wallet (wait for it to completely shut down, which may take a few minutes).  Next go back to the folder where your software stores the wallet currently in use. Replace the old wallet.dat with the backup from the new wallet.dat

Start your wallet back up.

Give the wallet a few minutes to re-synchronize and you'll see a single transaction received with your entire balance from your old wallet.

Keep both wallet.dat backups (old and new) in a safe place, and make sure you can tell which is which.

Oh thanks man. I didn't know that, and I retract my advice. I just learnt something new, lol.

Danny, I am using Bitcoin Core, and have encrypted my wallet with a strong passphrase.  Is having the passphrase sufficient protection even if someone else has my wallet.dat?  Would changing my passphrase increase my security, or should I just follow the steps you laid out?

yes, anyone who has access to your encrypted wallet.dat can try brute force the pass. But if your pass is original, and strong (various combination of numbers, special signs, min. 8 char. long) there is nothing to worry about.

also do not say to anybody how much btc this wallet control. no loot = nobody will try to break pass.

If the wallet was protected by a strong passphrase BEFORE you backed it up (and the passphrase is not stored with the backup), then you are probably safe from anyone accessing (spending or stealing) your bitcoins with the lost backup.  If you set the passphrase AFTER you backed up the wallet, then the backup can still access the bitcoins even without the passphrase.

Note, that if the backup is protected by a strong passphrase, this only protects you from someone using that wallet backup to spend or steal your bitcoins.  It does NOT keep them from seeing how many bitcoins you have.


No.  Changing your passphrase only changes access to the current wallet.  It does not change access to the backup.


There are two risks you need to decide between.

Risk 1
The person that finds your lost backup guesses your password or runs a program that tries many possible passwords until they stumble across yours.  The stronger your passphrase, the lower this risk.  If your passphrase is "password", then there is a good chance that your bitcoins will be stolen.  If your passphrase is "afwY$CA9Yh8afN94o#8h^awf;ohiaf a409 a08aw4y p2($", then you don't have as much to worry about.

Risk 2
You make a mistake in the process of creating a new wallet and sending the balance to the newly created wallet.  Your mistake causes you to permanently lose access to your bitcoins.

Only you know your passphrase, and only you know your technical aptitude.  So, only you can decide which is the greater risk.

Thanks for the help and information.

Why dont you back up the wallet next time in your email too? just put it a strong password and you will not have any problem.

well i think you are in a bit of problem as anyone get your usb and see bitcoin .. and if the user knows that the bitcoins worth dollars.. and he know how to sync that .. then you lost your bitcoins for sure if i m wrong please tell me..!

just curious whats the amount on there? If its less then 1 btc I wouldnt stress as much and consider a educational experience.

It is true that the person would be able to see the wallet has xxx bitcoin, but he need the passphrase to spend the bitcoin or get the private keys. (Please check post 7 by DannyHamilton)

If you have access to someone's wallet.dat file from Bitcoin-QT you can copying it onto you machine and see the transactions and value, Bitcoin-QT doesn't unlock the wallet for spending until the correct passphrase is entered as Danny noted.

If you have a really strong passphrase you could keep it online in an email or cloud, perhaps might be a good idea to rename the file to something like invoice.txt or something.

I'm not sure what is wrong with his suggestion, why would keeping private keys not be good ?

If you have access to the wallet.dat file, it won't be diffcult to dump out the encrypted information for you to see (even though your wallet is encrypted with a strong password). Then we can see which address that holds the money. Once it is found, use blockchain to know how much money in there.

I would say difficulty depends on password length and complexity.  I personally would make new wallet send BTC to it and encrypt it, and turn on two factor authentication.

When did they add two factor authorization to Bitcoin Core?

What is the second authorization factor?

Should be good to go once you've moved coins to an address you solely control.

At the time that the advice was given, it was not known yet what wallet the OP was using, or if the backup was protected with a strong password.

If the OP was using Bitcoin Core, and the backup was not password protected, then creating another address in the same wallet would not prevent someone from stealing the bitcoins if they found the backup.

You're wrong.

It depends on the Bitcoin wallet in use and the security it provides that is the strength of the passphrase.

Please be more careful, you could get hacked if not properly secured.