Bitcoin Forum

Have a few questions about Bitcoin core wallet, the main one, the firstborn son.

1) For maximum security and anonimity, I'm gonna use just one address for each transaction. So keeping every single private key may be a bit problem for me, actually no need of it, methinks. Please correct me if I'm wrong. So creating new address for every transaction can cause a problem for me? Any kind of problem I mean, just as an example, it can be longer sync time, or something like that.

2) I was an XMR guy actually. But recently sold for some reasons and planned to buy some btcs. Well, when I use XMR wallet (CLI/GUI), they give me private key of the wallet and so I can open my wallet with any other type of wallet such as Android/iOS ones or any lightweight one. I just need a private key of that wallet. But Bitcoin Core, itself, gives us only wallet.dat. So how can I reach my wallet on any other device? Or just as an example, I'm in hurry and I need to open my wallet on my android phone. How can I open it? I have used different addresses for each transactions. So basically I have 100 bits in my x address, 200 bits in my y address, 300 bits in my z addres... go on... So should I write down private key of every single address that I have?

3) I keep copying wallet.dat file to safe USB device after each transaction. Is that the only thing that I have to do?

4) Is there any other thing that I should know about Bitcoin core wallet?

Thank you!

No problems, just a larger wallet.dat.

There is no direct way to use that file on a mobile phone, if anywhere. You need your individual private keys or your master private key.

That is completely necessary. You need to encrypt it on the following events:
1) Wallet.dat creation.
2) Wallet.dat encryption.
3) Keypool renewal.

Yup that was what I think as well, I need individual private keys, so basically I need to keep every private key of my addresses, but wait, what is "master private key"?

Thanks for your answers. Really helped!

Also just in case,

Is there any other thing that I should know about Bitcoin core wallet I haven't mention above?

https://bitcoin.org/en/wallets-guide#term-master-private-key

Well, I wouldn't recommend running it on any external drive. Also, makes sure to properly shut it down before you turn off your system in any way. Both of these could cause corruptions which could require a full reindex, and those are painfully long.

Do you personally recommend write down private keys of every address that I have created just in case? wallet.dat "can" corrupt for some reasons and if ever happens, I will need private keys of my addresses, right?

Yes, you will need your private keys to spend the coins. The corruption Lauda mentioned affects the blockchain data; not your wallet. It might be easier for you to copy the wallet file to a few different data storage devices after encrypting them with VeraCrypt than writing the Master Private Key down. Other wallets give users a mnemonic passphrase (12/24 words) which can be used for wallet recovery.

Syncing now, it's going faster than I thought.

Thought I will need only wallet passphrase for sending bitcoin. Will I need private keys for sending bitcoin as well?

It seems I have to rethink about creating new address for each transaction lol. I run a cafe and I just started to accept bitcoin as a payment method.

Also when I send coins, which wallet will I use? One of my depo addresses? or what?

You either need you wallet file + passphrase or only private keys to spend your funds. The wallet file contains your private keys and it is encrypted with your passphrase.


One or a few of your addresses will participate in the transaction depending on the number of coins you want to spend. Let's say you want to send 0.15 BTC but you received 0.1 BTC to two different addresses. Both of these addresses will participate in the transaction and the remaining 0.05 BTC minus the transaction fee will be returned to your change address.

Got it. Thank you!

Last question then. Bitcoin core already comes with wallet.dat in its wallets file. Do I need to do "File" and "Backup Wallet" again?

There is no need to back up the wallet file again as long as you don't import any private keys. I don't think you are going to do it. Back up your wallet once, copy the file to multiple devices, optionally encrypt them and don't forget the passphrase.

old blocks were empty, so they're fast (and sync starts with old blocks)

blocks 400,000 - 600,000 are much fuller, they're slow to sync.

Is that possible to occur "corrupting" in wallet.dat file for some reasons? Did it happen before?

If I use different address for every deposit, well, I'll have bunch of addresses so keeping every damn private keys of them should be pain in the ass. That's why I'm asking.

Yes, there's probably an unknown number of potential causes for file corruption. It's irrelevant if you have a valid backup of it though; you'd just have to rescan the old backup wallet to get the latest transaction history. Keep in mind that you'll lose address labels though.


Just keep wallet.dat backups. Export private keys only for things when you need it elsewhere.

Got it. Thank you for your detailed answers. Reading your every post since yesterday. Sold my all XMR for BTC and I was all %100 on XMR since 2017. Was XMR maximalist. Things changed for me. Changed my mind, and I'm accumulating BTC for a while. I don't think that I will buy any other shit besides BTC. After reading your posts, I think I decide right lol.

I have one more question.

I'm using bitcoinfees.earn for checking current fee but Bitcoin core uses kb instead of byte. How can I convert it or how to calculate basically?

1 kb = 1000 byte.

Just multiply.

I also like to use https://coinb.in/#fees which shows some approximation of how much (in BTC) you will pay.

You don't have to use and external site to calculate your fees. When you want to send Bitcoins, just use the floating fee feature available in the client. You should be able to get a fairly accurate estimate of the current network conditions and be able to get your coins confirmed in a reasonable period of time.

So recommended fee is ok to use?

Also how many conf. do I need? Can I adjust it as 1 conf.?

Yes. Bitcoin Core's recommended fee is derived from your client's perception of the network's condition (ie. Having a more busy network would naturally require a larger fee per size since miners prioritise the higher fees.)

One confirmations is more than enough for most transactions. The more confirmation there is, the harder it is to reverse the transaction.

I mean, when I receive a transaction, it will be deposited after one confirmation? Can I adjust it? Just as an example, I want to make it 3 confirmation before I use it, can I do that or is it default and it's 1 conf?

When you receive a transaction, the transaction will appear in your wallet instantaneously (without any confirmations). By default, you can only spend the inputs after one confirmation and that isn't changeable. You can only change it with a change to the source code and building it yourself (AFAIK). After one confirmation, your wallet will be able to choose that input to be used.

It shouldn't be that much of a problem since a confirmation is relatively safe from double spending and there is no problem with you spending a transaction that has only one confirmation. You can always choose to select the inputs to be spent using the coin choose feature in the wallet.

If you are downloading 250+ GB (the whole blockchain), then a wallet.dat that becomes about 10 megabytes isn't very big in comparison. You should be able to back that up using any tool, compressor, winzip, rar, or whatever.

If you are using Bitcoin core for the first time this year, then your wallet is an HD wallet, and you only need to back it up once. I'd probably make another backup a month from now after you have been using it, just so you keep all the labels and that backup is done after you've used encryption on it.

If you've used Bitcoin Core since way back when, the wallet.dat could still be using random keys, in which case you need a backup after every transaction (beyond the first hundred).. My wallet is like that right now, I might eventually just move over all my old coins to a brand new wallet and just keep the old wallet backed up just in case.

I'm using it first time. I was going to save and replace it with old wallet.dat after every each transaction actually but doing it only once is enough now?

You don't need to replace the backed up wallet file as long as you don't import any new private keys.

So basically, if I use same address for every transaction, no need to copy wallet.dat after each transaction, right?

Also does Bitcoin core itself create a new address for every withdraw? I noticed that I have different sending and receiving addresses, so how does it work exactly?

Yes, the same applies if you use another address which belongs to your wallet by default.


You can reuse previously used addresses. A new address is provided in the 'Receive' tab if you use the previous one or/and generate a new invoice. Bitcoin Core should also generate a change address if you don't use up the whole input. It's a privacy enhancement.

That's the gist of it. Your wallet.dat holds your private key, unless you import a new one. You should be good.

What do you mean by "withdraw" ? Sending transactions out of your wallet or receiving them from a source? Unless you request a payment specifically, an address should be re-usable and there forever. You can view all of your addresses Window > Receiving Addresses.

You do not want to use the same address for every transaction, or for more than 2 transactions (first to receive, second to send.)

If you use Core now, you most likely have an HD wallet. What this means is that you need to back this up once after you have encrypted your wallet. If you add any labels or descriptions to your wallet addresses (like who you gave them to, what you paid for, etc) you may want to back up the wallet.dat every now and then, maybe once a month or once every two weeks.

If you withdraw from an exchange or other website, you should always use a brand new address. If you accept payment from anyone, you should give them a brand new address.

The only reason to reuse an address is if you are accepting payments or donations or tips from many people and can't give each one of them individual addresses, so you post an address and everyone sends to that one. (or you are running some sort of game, or raffle, or fund raiser, or similar situation.)

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I mean, sending bitcoin to a human being. For an example, let's say I have 1 BTC totally. 0.1 in one of my addresses, 0.2 in another one, 0.1 in another one etc. Totally 1 BTC. So when I send 0.5 BTC to someone, which address will Bitcoin core use as a sender? That was what I meant.


What does "HD" mean?

Also when you talk and recommend that don't use same address for every transaction, it's totally about privacy perspective, isn't it? Is there any other thing that I have to think about that recommendation?

All of them. Bitcoin-qt will create a transaction with multiple inputs to one output (the person you are sending the coin.)

HD Wallet = Hierarchical Deterministic Wallet. Rather than having 1 private key for 1 address, HD wallets have 12 word seeds that contain ALL your private keys and all your addresses. You can have unlimited addresses and keeping the 12-word safe and secure is enough.

"Don't use the same address" is mostly seen from a privacy perspective yes.

From your personal perspective, no need to export that seed, right? I mean, I can see that 12-word seed by using console but keeping wallet.dat safe is enough?

Your wallet.dat will have everything you need.

It doesn't have to be a 12 word mnemonic phrase, that's BIP39 (https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) and wasn't used by Bitcoin Core.
Bitcoin Core's new (some old) wallets are Hierarchical Deterministic (HD) but doesn't have a mnemonic phrase, it follows BIP32 (https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki) but not the one generated from a BIP39 seed.

More info in the links.

The link you provided shows an altcoin called 'Bitcoin Core' which has nothing to do with the Bitcoin Core which is a Bitcoin client.


Bitcoin Core (https://bitcoin.org/en/download) is available only for PC. It downloads and verifies every single block that has ever been mined (over 200 GB of data). You can either run it in a pruned mode (https://coinguides.org/bitcoin-blockchain-pruning/) or use Electrum (https://electrum.org/#home) which is a light-weight client. If you are looking for a decent Android alternative then consider using Samourai Wallet (https://samouraiwallet.com/).

You should create a separate thread for your questions. Edit: Ah, I have checked your other post. It's just an ad.