Bitcoin Forum

Hello guys,

I want to store my BTC on a 16MB SD card, because of shitty Windows (it's iikely, that my Windows will destroy itself in the next time again). But I have to use Windows, because of the games.

It must be safe and usable with Linux too (and of course it should be free). Therefore I would use TrueCrypt to encrypt the memory card, but I don't know how to store the BTC there.

What about a paper wallet, is that safe and free?

I hope you can answer my question :)

A paper wallet is safe and free as long as you have a piece of paper and a pen, and if you don't lose the paper. You might as well stick the paper into a safe.

16 mb is more than enough to hold your wallet file.
But the blockchain is huge.
just make sure you use a program like electrum multibit or armory.

I'm using MultiBit. Do I only have to copy the wallet.dat onto the SD card?

And what if I want to restore it, but the balance is not the correct one (e.g. because I got earnings from mining, or bought something)?
I think a paper wallet would be more safe, because it can't get outdated, but the problem is, I can't backup all my BTC ....

Would it be possible, to sync the wallet.dat on my PC with the google drive or other cloud services? I think this would be the best backup.

There is no difference. You wallet cannot get outdated. Bitcoins are not stored in the file.

That means I only have to copy the wallet.dat ONCE to the SD card, and it's a backup "forever"?

more or less, from what I read the wallet.dat stores your private keys(the numbers used to SPEND coins from your addresses) and you can store your private keys even on paper https://en.bitcoin.it/wiki/Paper_wallet (https://en.bitcoin.it/wiki/Paper_wallet)

if you're paranoic, create a bunch of addresses(the ones from receive tab) and store them in a text file, backup wallet.dat and delete wallet application and downloaded chain block
send your coins to addresses and monitor them with block explorers
when you're ready to spend install wallet app, sync it, replace wallet.dat and happy spending :)

IMPORTANT!

If you are using a non-deterministic wallet then you will need to back it up every time new keys are created. You can determine if the wallet needs backing up again by checking if the wallet.dat file has been modified. Alternatively use a deterministic wallet, as the seed only needs to be backed up once.

I'm using Multibit. Windows says, that my multibit.wallet (must be the wallet.dat of Multibit) was last modified today.

Which wallet do I have to use, that my wallet.dat doesn't has to be modified? Can you recommend me such a wallet?

I think electrum will be best for you.  Make sure you write down the secret phrase in case you lose your usb drive.

Use electrum. Either backup deafult.wallet or jot down the private key.

Can I use Vanitygen with electrum? Or import my private keys from MultiBit?

Would be great, if Vanitygen can be used for this (don't want these lame random adresses).

You just need a text file for vanitygen addresses, not a wallet. 

No, I want to import some vanitygen adresses into Electrum, that I can receive BTC with these "cool" adresses.

You take the private keys from VanityGen and import them into Electrum.

Have done this, but Electrum warned me, that imported adresses won't be restored with my seed.
But that is not important, since I copy wallet.dat to the SD card, am I right?

Just keep the private keys in a text file.  You don't need to import them to receive bitcoins, they're always able to receive bitcoins.

I think writing them down would be safer, there is a risk that you will get keylogged.

That is unimportant, it only means that if your computer explodes, entering your secret seed on another Electrum client will not restore your Vanity Address.

Think I don't understand the Bitcoin payment completely.

I have copied now the private key from vanitygen to electrum. If I receive Bitcoin with the vanity adress, will they go to my normal wallet, where my mining, trading earnings etc. from other adresses go to or is there a wallet for every adress?
In multibit every adress pointed to the same wallet, it was only, that you can see, where the Bitcoins are from.

Now I have to copy the wallet.dat and the private key of my vanity adress to the sd card? Is there anything else, I have to copy?
So, if my computer burns, the Bitcoins/private adresses are safe on the sd card and ONLY my PC is dead?

Yes.



No. What happens is that electrum addresses are somewhat "linked" in the sense that they are generated from a seed. Privkeys that you import don't belong to this scheme so aren't restored from the seed after a crash. That's why you should either keep those privkeys or backup the full electrum wallet instead of only the seed.

Backing up both the wallet and the imported privkeys, on the other hand, doesn't do any harm!

i am same question interest  ???  :'( ::)
if make format and delite posible make this restore walet or fix

But what happens if I can't restore the vanity adress? The received Bitcoins should stay in my wallet, even if the private key of the vanity adress gets lost, or not?

Wallet is just a collection of keys.  You need the keys to spend the coins.  Don't worry about the wallet, just worry about the keys for your vanity addresses.  Really though don't use vanity addresses.

Hmm, okay... I will delete the vanity adress. So if I copy the wallet.dat onto the sd and create some adresses later,  they will be safe too?

I don't understand, why I need to recover the adresses for SPENDING Bitcoin. Can't I just spend them with another adress (which I can create, after my PC has crashed), or is there something like a "master adress", which is used for sending Bitcoins?

Hmm think of it like this.

Each address is a unique account.  It has a balance, say 5 BTC.  To spend that BTC you need the key to the address.

You will have more than one address.  Each has their own balances.  Each has their own key.  If you don't have the key corresponding to a certain address you can't spend the BTC stored in that address.

Because you will have many addresses, like 10-100, you group them together in a wallet.  A wallet is just a file (like wallet.dat) that has a list of your addresses and their keys.

Because it's annoying to have to keep track of 100 addresses and 100 keys, there are programs, like electrum, that allow you to only keep track of one long master key (the seed).  Using this seed and some math that I don't understand, the program can generate millions of addresses and corresponding keys.  Because it can generate them from the seed, this allows you to have multiple addresses and keys but only one master seed to have to backup.  Of course you should also backup the wallet file (they're not all called wallet.dat -- it depends on the program you're using).

If you don't use a program like electrum you need to backup each address and its corresponding key.  If you lose the key to the address you can't spend the coins located there.  There are lots of coins that are "lost" forever because people lost the key to them.

But what if I receive 5 BTC with adress "123" and 5 BTC with adress "abc"?
I can spend the sum of 10 BTC from a third adress "xyz", if all three adresses are in the same wallet. Even if I never received a single Bitcoin with adress "xyz" .....

So if I have written down the seed and backed up my wallet.dat (or how it's named) my Bitcoins are safe from getting lost by PC crash, even if I create a new adress and receive Bitcoin with it later than the PC crash? Or am I wrong?

You cannot send BTC from xyz if your funds are in 123 and abc. Also, your wallet is safe, unless someone gets your private key and spends your bitcoins.

If you have $1000 in checking account abc and $0 in checking account xyz, try to write a check for $1000 from xyz and see how that goes.

Ah, finally I understood  ::)

But another last question:

In Multibit I could spend my complete wallet balance at once. At first It sent the BTC received with other adresses to the first adress and then to the receiving adress. Everything full automatic. Is this in Electrum automatic too, or do I have to do this manually?
e.g. 1 BTC is on adress 123, 1.5 BTC are on abc and 0.5 on xyz - now I could send all 3 BTC at once. It sent 1.5 + 0.5 to adress 123 and then all 3 to the adress, receiving it. Everything in one transaction.

Yes. That happens with almost all wallets, and no hassle required.

That's why we use wallets.  Because they have info on all of our addresses (accounts) and all the corresponding keys, we just tell it to send our desired amount and it can send from multiple addresses that add up to our desired amount.