Offline paper wallet
April 7, 2013 4:20 PM
Bitcoin paper wallet?
Ok, so I just purchased a bitcoin, but even after reading countless posts about how to secure them, I'm still not entirely sure how it all works. I have a good password and so on, but I'm aware that this doesn't protect me from a server side attack (e.g. what just happened to instawallet). Any mefites here able to shed some light on the following:
1) How do I create a paper wallet? The guidelines for the paper wallet on blockchain.info (here) don't seem to relate to the screens I see on my computer. For ultimate security, I'm supposed to be 'offline' to do this, but the blockchain website doesn't seem to reflect what I should be seeing if I follow the instructions.
2) Do I have to create a paper wallet first, then send money to it, or do I create a new address, send money to that address, *then* create the paper wallet? Is it as simple as 'send BTC to X' under the 'send money' option?
3) How would I then check the balance of the paper wallet to make sure that the BTC went over?
4) How do I delete the 'private key' of the paper wallet address on blockchain.info? The only way I can see how to do it is to 'archive' the address and delete it from there, but I don't think that's what I'm meant to do. There's supposed to be a little gear thing which enables the option to delete the private key, but I don't see it (see point 1 above).
5) I have an account with blockchain.info, but how does this site interface with other bitcoin websites? My address is, presumably, not unique to blockchain.info? Or is it?
Please, talk me through this as though I'm a child, preferably with shiny diagrams and easy-to-follow instructions, because I feel really dumb for simply. not. getting. this. Apologies if any (all?) of this is difficult to follow...
Ok, so I just purchased a bitcoin, but even after reading countless posts about how to secure them, I'm still not entirely sure how it all works. I have a good password and so on, but I'm aware that this doesn't protect me from a server side attack (e.g. what just happened to instawallet). Any mefites here able to shed some light on the following:
1) How do I create a paper wallet? The guidelines for the paper wallet on blockchain.info (here) don't seem to relate to the screens I see on my computer. For ultimate security, I'm supposed to be 'offline' to do this, but the blockchain website doesn't seem to reflect what I should be seeing if I follow the instructions.
2) Do I have to create a paper wallet first, then send money to it, or do I create a new address, send money to that address, *then* create the paper wallet? Is it as simple as 'send BTC to X' under the 'send money' option?
3) How would I then check the balance of the paper wallet to make sure that the BTC went over?
4) How do I delete the 'private key' of the paper wallet address on blockchain.info? The only way I can see how to do it is to 'archive' the address and delete it from there, but I don't think that's what I'm meant to do. There's supposed to be a little gear thing which enables the option to delete the private key, but I don't see it (see point 1 above).
5) I have an account with blockchain.info, but how does this site interface with other bitcoin websites? My address is, presumably, not unique to blockchain.info? Or is it?
Please, talk me through this as though I'm a child, preferably with shiny diagrams and easy-to-follow instructions, because I feel really dumb for simply. not. getting. this. Apologies if any (all?) of this is difficult to follow...
Because all the transactions are public, you can find the balance of any public address by scanning the whole blockchain for all the transactions that send coins to that address and all the transactions that have coins sent from that address. The most convenient way is to just put the address in the search field at blockchain.info and that will show you the current balance at the top (and all the transactions).
When you have a "wallet" of any sort, that works in exactly the same way - it just scans the blockchain for all transactions involving your addresses and shows you a final balance. For convenience some sites like blockchain allow you to add a "watching address" which shows you the balance but doesn't let you spend it. So to see the balance the wallet doesn't actually have to know the private key; this is only needed to send the coin somewhere else.
So in the simplest way to make a paper wallet is just to generate a new private key and corresponding public key, write them both down, then send your bitcoin to that address. You never need to have the private key in your wallet (but be TRIPLE SURE YOU HAVE IT SOMEWHERE). You can check the balance just by searching on blockchain.info.
https://www.bitaddress.org/ is nice and simple for generating keys (there's no difference between the first tab and the "paper wallet" tab except formatting for printing).
Depending on your paranoia you can generate your key offline on a clean machine with TEMPEST shielding or just say fuck it chances are it's fine.
When you want to spend out of your paper wallet you need to sign a transaction with the private key, personally I would just import it into blockchain.info, send what I needed and send everything else to a new paper wallet rather than try and do all the offline transaction gubbins.
Remember if you lose the private key you lose all your money, practice with 0.01 BTC and make sure you can get it back (you'll lose some satoshis to transaction fees but it's worth it to be sure you understand it all).
posted by samj at 12:49 AM on April 8, 2013
When you have a "wallet" of any sort, that works in exactly the same way - it just scans the blockchain for all transactions involving your addresses and shows you a final balance. For convenience some sites like blockchain allow you to add a "watching address" which shows you the balance but doesn't let you spend it. So to see the balance the wallet doesn't actually have to know the private key; this is only needed to send the coin somewhere else.
So in the simplest way to make a paper wallet is just to generate a new private key and corresponding public key, write them both down, then send your bitcoin to that address. You never need to have the private key in your wallet (but be TRIPLE SURE YOU HAVE IT SOMEWHERE). You can check the balance just by searching on blockchain.info.
https://www.bitaddress.org/ is nice and simple for generating keys (there's no difference between the first tab and the "paper wallet" tab except formatting for printing).
Depending on your paranoia you can generate your key offline on a clean machine with TEMPEST shielding or just say fuck it chances are it's fine.
When you want to spend out of your paper wallet you need to sign a transaction with the private key, personally I would just import it into blockchain.info, send what I needed and send everything else to a new paper wallet rather than try and do all the offline transaction gubbins.
Remember if you lose the private key you lose all your money, practice with 0.01 BTC and make sure you can get it back (you'll lose some satoshis to transaction fees but it's worth it to be sure you understand it all).
posted by samj at 12:49 AM on April 8, 2013
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This is the same information that would be in your wallet.dat file that bitcoind uses. JSON is how blockchain stores the data that you’re seeing in your paper wallet so that the robot computer banker gods can read those hashes with context.
If you want to test this stuff out btw, just transfer some of your BTC to a Mt Gox account or something.
posted by oceanjesse at 6:26 PM on April 7, 2013