Bitcoin Forum

Suppose I have lot of bitcoins on offline generated address and private key stored on paper wallet.

Now I want to spend/sell these bitcoins. What are secure and effective ways to do this?

I will need to load the bitcoins at this offline address into some wallet (say Electrum). So do I need to load all the bitcoins, or only some? How do I do it?

So I have to EITHER sign an offline transaction made by Electrum (for sending some btc to an exchange) http://docs.electrum.org/en/latest/coldstorage.html or SWEEP them to Electrum on online computer (send all btc to electrum wallet) http://docs.electrum.org/en/latest/faq.html#can-i-sweep-private-keys-from-other-bitcoin-clients

Am I right?

What the ways to spend such large number of bitcoins on offline address and private key?

I would say the best option is to import the address to e.g. electrum. Send out the amount you want to spend/sell (to either exchange or any other wallet you are using regularly) and then delete this wallet file.

Alternatively you can sweep the address to the wallet but this makes a regular transaction (it simply sends all the bitcoins to new address in that wallet ).

Edit:
Just notice you have updated the OP.
Yes, thats correct.
Signing offline transaction and pushing it is actually the most secure way. If you sign it using offline device.

You can't spend, transact any Bitcoins while you are offline, the easiest way after Electrum sweep and or import is by trying blockchain.info (http://blockchain.info) import your address as watch only and when you click on send or spend it will ask you for private key.
Stop being paranoia and trust me when I tell you, no body is ought to get your coins that easy.
Now tell me how many BTC you have BTW? I could pick some of them from your shoulders if you feel burdened. lol

Entering your private key into an online computer kind of defeats the whole purpose of cold storage. The best way is to sign a transaction using an offline computer, copy the signed message and then broadcast it.
It is best to be paranoid while dealing with bitcoins.

Thanks! So to sign a transaction using an offline computer, I would need a bitcoin wallet installed on Offline computer. Right? If I just have a paper wallet, then?

Back in the days when i used to deposit all my bitcoins in a paper wallet, i just withdraw it by having an account in blockchain web wallet and then i will just go the settings and i will just import my privatekeys by scanning the barcode from the paper wallet that i generated. It was easy and also fast in redeeming your bitcoins, you just need to make sure that the privatekeys are safe and not been used even once.

Use Bitcoin Armory and sign transactions offline with your private keys held on an air gaped computer.

That is correct. You need to have a bitcoin wallet, like Electrum, installed on your offline computer.
Then you can import your private keys and sign a transaction.

Right.
But you have to get the private key to this offline wallet anyway ( this is where I found paper wallets pretty unhandy ). You have to scan the QR code ( if you don't want to type it in by hand) which I found the most easy way to leak (revealed QR is dangerous IMO). And then you have to get the signed tx to online device.

So my advice is to import the wallet to online device spend the coins, throw the paper wallet away and make a new one.

Being extremely cautious is always good. Especially when dealing with bigger amounts.
If you really have a bigger amounts I highly recommend you to purchase hardware wallet (it's much easier to use and even more secure)

Yeah you need to have a electrum or multibit wallet installed on your computer. Once after this you can further process by importing all the bitcoin towards the particular wallet using the private keys and once again sign the transaction, which is the easiest process.

just FYI sweeping is not a strange thing. it means making a new key that the sweeper wallet holds and send the funds from the imported key to that new key.

for spending you don't necessarily need to do this. you can import the old private key then make a new private key the same way you did the first one (paper wallet or others) then send the funds to the wherever you want (the exchange for example) and send the rest to the new private key.

So this is what I've figured:

• Download bitaddress.org and copy to offline computer. Generate private key, address offline from it. Make paper wallet
• Send btc to this address
• Setup Electrum wallet with a seed on offline and online computer.
• SWEEP the key into OFFLINE Electrum wallet. This will not import the key, but transfer the bitcoins from that address to the electrum wallet address.
• Sign an offline transaction made by Electrum (to send some btc to a exchange)
  
• Execute the signed transaction on Online computer Electrum

Am I doing anything incorrect?

In the SWEEP the key into OFFLINE Electrum wallet step, since the wallet is offline, Sweep won't happen, right? What should I do then?

So complicated and so useles. Can't you see the very first step ruins it all? Using online service to generate paperwallet is bad decision.

Try it this way.
1-  Install electrum to OFFLINE DEVICE, generate address&key pair, print it and DELETE THE WALLET -  Now you have created a paper wallet.
2 - Send BTC to this address. - Now you have paper wallet with BTC.
3 - Instead of SWEEP ( which will cost you transaction fee)  use the IMPORT to OFFLINE DEVICE with wallet - Now you have offline wallet where you can sign the transaction.
4 - Sign the transaction and DELETE the OFFLINE wallet. - Now you have signed transaction
5 - Copy SIGNED TX to any ONLINE device with and push it (no need to have wallet installed here, use any pushing service e.g blockr.io )

Note that importing address to offline wallet not ruin the paper wallet itself. You can use it again.

Step1 - How do you print address and key from Electrum?

Right click to given address / private key.

If you wish to import a private key, you can do that for both paper or other type wallet. paper wallet's key is no longer completely secured and it is able to be compromised once it has been uploaded to any online wallet. Main use of having the private key  (or paper wallet) yourself and no one else can ever have access to it.

you are confusing SWEEP with IMPORT.
these are two different functions.
- you sweep the private key if you want to have them in your wallet. in this case you need to broadcast the transaction for it to complete.
- you import the private key in your wallet if you want to spend them for example if you want to send your funds to an exchange to sell.

for sweeping you use an electrum wallet that was generated with a seed and you have a back up of that seed.
for importing you create a new wallet and use your private key to make the wallet. the wiki has these steps with pictures.

How is this method:

https://www.cryptocompare.com/wallets/guides/how-to-make-a-bitcoin-offline-transaction/

https://www.youtube.com/watch?v=DQumISxkJsQ

Is this all one needs to do, or there could be better alternative somewhere there?

I just have one question. Why do I have to create a transaction on an online computer and then transfer the transaction to offline computer. Can I not just create the transaction on the offline computer?

I've used the cold storage spending option from Mycelium a few times without any mishaps. I wouldn't do it with a paper wallet containing a great deal, but for relatively piddling amounts it's fine. It also handles the change issue perfectly as well.

If you know which inputs you are going to spend, and you know what the Txout-script (also known as the scriptPubKey) is for each input, then you can just create the transaction on the offline computer.

If you don't know how to do that, then it is just easier to use an online wallet that can look that information up in the blockchain for you and build the transaction.  IT saves you a lot of effort and helps reduce the opportunity for mistakes.