Topic: Help - Backing Up A Cold Wallet (Read 567 times)

That is also valid. However, I would recommend making sure that the txn that the site creates is trustworthy before signing and saving it.

Well, that's just a secure wallet. A cold wallet is slightly different, and more secure:

1. A computer is set up with a clean operating system and is not connected to the Internet.
2. A Bitcoin wallet is set up, and a Bitcoin address is generated. A backup should be made to some sort of secure medium (e.g. flash drive in a bank vault)
3. The Bitcoin address, but not the private key is written down on paper, screenshot, etc.
4. Coins are deposited to that address. This does not need the cold storage machine does not need to be connected or powered on. Coins can be added at any time.
5. To spend coins, the cold storage wallet is connected to the Internet, allowed to sync, and then the coins are sent. The wallet can still be used as a secure wallet, but not as a cold storage wallet.

One of the simple ways to back up your wallet is to create an nLockTime transaction to another address that you own. Just make sure you have control of the other address that you are specifying in the nLockTime transaction. You could use a coinbase address or use a suredbits address.

Okay, I appreciate your help, thank you
I think I'll look more in-depth online about cold-storage, I always thought it was as simple as making a wallet on a flash drive and only using it on secure computers, lol.
Thanks

No, when you send a transaction, some leftover coins are sent back to a new address in your wallet. Your existing addresses are not modified, but some coins will end up in new addresses that are in your wallet.

The key for any specific address never changes, but new addresses and thus new keys are created by your wallet and used to store some coins.

In the end, I'd just make backups every 50 or so transactions sent from your wallet, and not delete anything for any reason (except possibly the block chain data after you have successfully backed up your keys and verified that the backup works).

I HIGHLY suggest being careful on deleting everything.   If you have a second computer that is safe you might try to test private key.

By testing you can see if it works.  It should let you import key on a lightweight wallet and show your BTC amount you have.   By testing it you know you are not losing it all by deleting.  If you just delete it would be very bad if you don't have all the info.

What do you mean by "an address for receiving change"?
In summary, my wallet has around 100 keys, with 1 key being used for each transaction. When I have conducted 100 transactions, a new set of private keys are generated for my Bitcoin address. Therefore my private keys in backup (which were made over 100 transactions ago) would not match the Bitcoin addresses current set of private keys, is that correct?

Not exactly. Your wallet generates 100 keys and stores them in the wallet, ready to be used when an address for receiving change is generated. Those keys are backed up along with the visible ones. As keys are used, the pool is replenished with new keys (that were not backed up yet)

Once 100 keys are used up, the next address generated is NOT one stored in the backup.

You can delete everything in your Bitcoin data directory, other than wallet.dat. I would not export to text files, as the wallet.dat file is the same content. Just save the wallet.dat to your flash drive. If you just back up private keys, you won't back up the pool of keys used for change addresses.

You can either copy the wallet.dat file, or open Bitcoin-qt and click File->back up wallet (or some similar option, can't remember the name exactly).

Restore by renaming the current wallet.dat in the Bitcoin data directory, and copying the backed up one in, or in the gui with file>restore wallet.

So the new private keys are made after around every 100 transactions?
Does this mean that I could delete everything to do with my wallet apart from the private keys, then recover it using only the private keys? If so, then surely I only need to put my private keys onto my memory sticks in a .txt or something, then I could just re-obtain the private keys every so often and put the frsh ones on the flash drives?
Thanks

A private key is a piece of information that is required to do anything with your bitcoins. It is the data that must be protected from theft or loss (as if someone else has it they can spend/steal your coins, and if you do not have access to it, you cannot use your coins at all)

Private keys are stored in a wallet file. Bitcoin-qt stores them in a file called wallet.dat, while Multibit stores it in a different file format.

The important thing to know about Bitcoin-qt is that it is not an HD wallet, which means that you must make backups periodically after use. When you are storing coins in cold storage, the address that holds the coins has a private key, that is stored offline. However, when you start spending coins from that wallet, technical reasons make it that NEW private keys are generated for NEW addresses to store change. Because these NEW private keys are not part of an old backup, you will need to make backups occasionally (at least once every 100 transactions, based on default settings, but I recommend doing it more often)


No, since the wallet file itself isn't affected by synchronizing. It's simply a list of keys. Synchronizing is needed to keep your wallet's understanding of the balance of your addresses of those keys up-to-date with the network's consensus on the balance of your addresses. If you restore a wallet to a machine that IS up-to-date, it will not need to actually sync (although it will rescan the ledger to locate any transactions that apply to your restored wallet)

 However, you might need to update if you use any copy with a bitcoin-qt installation that isn't up-to-date. It will fetch the newest parts of the blockchain ledger.

I don't really get what a private key is. So not all wallet programs use a wallet.dat file?

If you get the private key you could make a paper wallet.  Store the paper wallet is safe place.  And if ever needed you can get info off of it.

As far as wallet.dat you could put it on multiple USB drives to store.   I would also put private key on it, some wallet will not use wallet.dat but private key. Again keep them safe where you store and don't plug into a every day surfing computer.

Hi,
Currently, I'm thinking of putting some of my BTC into a cold wallet and treating it like a savings account. Of course, I would like to backup this wallet, but I read something that concerned me.

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Example:
I have 2 copies of the same wallet.dat, copy 1 and copy 2. If I send BTC with copy 1 and do not have copy 2 open at the same time, will copy 2 no longer work? If I receive funds and open copy 1 and let it update, will copy 2 also no longer work?

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I thought that is completely incorrect as surely both copies could just update from the block chain and none would EVER under ANY circumstances become unusable? However, I wanted to clarify before I make myself a cold wallet and back it up multiple times.
Cheers.