to control bitcoin, do you need just a passphrase, a wallet.dat, or both?

[James Bond]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

[linuxnewbie]

See https://bitcoin.org/en/choose-your-wallet.

You only get a wallet.dat file if you use the full Bitcoin client.

I would recommend using a web wallet for small amounts and a desktop wallet for large amounts.

With a web wallet, all you need is a username and password (to the extent that you trust them not to steal your money), and some of them (blockchain.info and strongcoin.com) also supposedly give you complete control over your private keys.

As for desktop wallets, I recommend Electrum. The electrum wallet also relies on a wallet file, called electrum.dat, which you need to have on your hard drive to spend your BTC. Electrum also has an interesting restore-from-seed feature, which you should look into.

[hilariousandco]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

Well you'll need a wallet or client to redeem the funds no mater where they're stored.

[serje]

Be my quest and remember the next pass phrase!

go in bitcoin-qt to help-debug-console

write

walletpassphrase yourpassphrase 120    //120 means the seconds the wallet will be unlocked because only after the wallet is unlocked you can export privkey
dumpprivkey yourbitcoinaddress           //the address you want to remember the passphrase for


if you can memorize it let me know .... but I would recommend you to just print it from a printer at home! and put it in a safety box! after that you can delete the wallet.dat file

[odolvlobo]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

A wallet holds one or more private keys. It does not hold bitcoins.

Holding a private key allows you to send bitcoins from an address.

A brain wallet is simply the case where you memorize a private key. In this case, your brain holds a private key so it is a wallet by definition -- a "brain" wallet. However, in this case you memorize a passphrase that is used to generate the private key and not the actual key.

People lose bitcoins when they lose a wallet file because they haven't backed up the wallet file or the private keys that it contains.

Please note that the passphrase used to unlock a wallet is simply the passphrase used to encrypt and decrypt the wallet file. It is not the same as a private key or a brain wallet pass phrase.

[Bizmark13]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

This thread might be of interest:

https://bitcointalk.org/index.php?topic=488560.0

I was a bit confused about this too but apparently, the private key is all that really matters. Your computer could burn to ashes tomorrow and you'd still be able to access your funds if you have your private key written down somewhere. In the case of brain wallets, a passphrase is memorized which is used to generate a unique private key but it's the private key that ultimately matters.

If you lose your computer but you have the wallet.dat file backed up somewhere then that can also be used to access your wallet since it contains the private keys of all the addresses in your wallet.

Some wallet programs like Electrum and Armory have a feature that lets you backup your entire wallet (ie. all your addresses and private keys) by writing down a short phrase called a seed. That way, if your computer is either lost or destroyed, you can still regenerate your wallet from this. Not sure exactly how it works though.

[James Bond]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

A wallet holds one or more private keys. It does not hold bitcoins.

Holding a private key allows you to send bitcoins from an address.

A brain wallet is simply the case where you memorize a private key. In this case, your brain holds a private key so it is a wallet by definition -- a "brain" wallet. However, in this case you memorize a passphrase that is used to generate the private key and not the actual key.

People lose bitcoins when they lose a wallet file because they haven't backed up the wallet file or the private keys that it contains.

Please note that the passphrase used to unlock a wallet is simply the passphrase used to encrypt and decrypt the wallet file. It is not the same as a private key or a brain wallet pass phrase.

Good answer, thanks. So, as I understand it, you only need the private key to send bitcoin from an address, whether that private key is stored on paper, in a wallet file, or in your brain. I was just reading the bitcoin wiki and it said that the address can be generated from the private key, so apparently you don't even need to store the address somewhere if you have the private key.

[serje]

I've heard of people losing bitcoin because they threw out a hard drive. And I've heard that you can control bitcoin with just a brain wallet (a memorized passphrase). Do you need just a passphrase, or do you also need a wallet.dat file (if you're not using an online wallet)? If someone could provide a simple explanation or point me to one I'd appreciate it.

A wallet holds one or more private keys. It does not hold bitcoins.

Holding a private key allows you to send bitcoins from an address.

A brain wallet is simply the case where you memorize a private key. In this case, your brain holds a private key so it is a wallet by definition -- a "brain" wallet. However, in this case you memorize a passphrase that is used to generate the private key and not the actual key.

People lose bitcoins when they lose a wallet file because they haven't backed up the wallet file or the private keys that it contains.

Please note that the passphrase used to unlock a wallet is simply the passphrase used to encrypt and decrypt the wallet file. It is not the same as a private key or a brain wallet pass phrase.

Good answer, thanks. So, as I understand it, you only need the private key to send bitcoin from an address, whether that private key is stored on paper, in a wallet file, or in your brain. I was just reading the bitcoin wiki and it said that the address can be generated from the private key, so apparently you don't even need to store the address somewhere if you have the private key.

True!

If you have the private key you have your BTC! but that one is hard to memorize! caps matter!

[James Bond]

This thread might be of interest:

https://bitcointalk.org/index.php?topic=488560.0

Yes, thanks, there's some interesting stuff in that thread too that isn't intuitive and I didn't understand at first:

... here's the thing that catches most people because they don't realize how Bitcoins work, first of all, a tl;dr, "When you spend any amount of money, the money will probably no longer be in the same address".

Longer version:-
It's impossible to spend less than the amount you received in a previous transaction, but, obviously, the majority of the time you won't want to spend the exact amount of a TXIN (or multiple ones combined), so, what do you do? You send the amount you want to spend to the receiver, then, you send the remainder ('change') back to yourself, normally, on a different address, meaning the private key for the last address is now worthless.

Personally, I recommend Armory (Or any other client that uses a pre-saved seed to generate keys), as, it fights this by using a seed which you print off to generate all addresses, this means even if you receive money on an address after paying, or, send change to a new address, that printed wallet two-line long string still saves all your funds.