'Change' wallets.

[Leahhhh]

I am about to transfer some BTC to my Blockchain account from a paper wallet. However, a thought came to me regarding the phrase 'change wallets'. I remember reading where if you only spend a portion of your coins, the remainder can be sent to a change wallet & in some cases they get lost. Suppose I had 2 BTC in my Blockchain account & transfer one to somewhere else, where will the other one go? I had intended sending the remaining coins back to a new paper wallet. Would this work or would they go to a change wallet? If so, where would I find it?

[TryNinja]

I believe it depends on the wallet you use. There are also options in such wallets that you can enable to make the change go back to the address of origin. Other wallets I believe will try to create a new address unrelated to the paper wallet and send the change there.

Did your transaction from the paper wallet have any change? And if so, which wallet did you use to send them to Blockchain.com?

Is this a real situation or just an hypothetical case?

[Leahhhh]

This is a real situation and I haven't done it yet; was about to when this jumped into my head. So, if I sent 1 BTC for example from my Blockchain wallet, the other one could be sent back to a wallet that I would have no access to? If I created a 2nd Blockchain wallet, would it come back to that? I really wanted to sell some of my holdings but now I am afraid to in case I lose the remainder.

[o_e_l_e_o]

Suppose I had 2 BTC in my Blockchain account & transfer one to somewhere else, where will the other one go?

The other 1 BTC would return to your Blockchain account and be available to you to send or spend elsewhere. If would automatically be returned to a newly generated change address within your wallet. There is no such thing as a "change wallet", only "change addresses" within a wallet. You can read the blockchain.com support page on this here: https://support.blockchain.com/hc/en-us/articles/360018566291-Change-addresses

Change addresses are most important to pay attention to when using a paper wallet. Since a paper wallet only contains one address, there is no "change address" to return unspent coins to, and some users have lost their change when only spending part of a paper wallet. It is generally best practice when using a paper wallet to spend it all at once.

Blockchain is a web wallet, and is generally a poor choice to use to store your funds though. A better option would be to use a hardware wallet, or failing that, a desktop wallet such as Electrum. With Electrum you can have full control over your change addresses, you can see them all, and even choose which ones to send to.

[Leahhhh]

I will be importing all that is in my paper wallet to my Blockchain account but I was hoping to then sell a small portion of that to someone else. (I have edited my original comment which probably gave the impression that I have already done this - I have done nothing yet). I am now afraid to send, let's say 25% of what is imported to my Blockchain wallet, in case the other 75% is sent somewhere where I can't access it. Looks like I might have to hold until it hopefully someday reaches a price where I'm happy to sell the whole amount at once.....can't take the risk.

[o_e_l_e_o]

-snip-

The step where you could potentially lose a portion of your money is going from paper wallet to blockchain wallet, not transferring out of the blockchain wallet.

Paper wallets only have one address. They do not have a change address to send to change to. If you try to transfer a portion of your funds out of a paper wallet, you may inadvertently transfer the change to an address you can't access. You can easily avoid this simply by sweeping the entire amount from your paper wallet to your blockchain wallet.

Transferring out of your blockchain wallet is safe from a change address point of view. Their software will automatically generate a new change address for you, which you control, inside your current wallet. Anything you don't spend will be automatically transferred back to this change address. From the point of view of your wallet interface, your change will never leave your wallet.

I'll say again though, I wouldn't be sweeping paper wallets to a web wallet. Choose a good desktop wallet instead.

[Leahhhh]

 ''There is no such thing as a "change wallet", only "change addresses" within a wallet. You can read the blockchain.com support page on this here: https://support.blockchain.com/hc/en-us/articles/360018566291-Change-addresses''

Would I need to know the private key for this change address?

[o_e_l_e_o]

Would I need to know the private key for this change wallet?

You don't actually need to "know" the private key, but you would need to have access to the private key to be able to spend the coins from the change address. The private key would be automatically generated and stored for you by blockchain.com, and you would be able to use it to sign a transaction simply by logging in to your blockchain.com account. The change address is part of the same wallet you would be spending from - each wallet can contain many addresses.

[Leahhhh]

So I would never have a long string of numbers and letters like I have with the keys for my paper wallet? Would I be able to access it in some way as long as I have my backup words? Sorry to sound so stupid, but this is complicated for someone who has never done it before.

[o_e_l_e_o]

So I would never have a long string of numbers and letters like I have with the keys for my paper wallet?

You could have them, if you wanted them, but there is no need to have them with a blockchain.com wallet. The wallet stores them for you and signs any transaction you want with them automatically in the background.

Would I be able to access it in some way as long as I have my backup words?

Yes. Provided you have correctly written down the 12 mnemonic words that blockchain.com generates for you, you can use these 12 words to derive your wallet's seed, all therefore all its private keys, and all its addresses, if you so wish.

[Leahhhh]

Thanks o_e_l_e_o for your advice. I only did this once before, and in that case I  transferred all I had in my paper wallet to my Blockchain account and straight on to somewhere else. Never had to consider change wallets before but I'm looking into Electrum now too as you suggested.

[o_e_l_e_o]

Thanks o_e_l_e_o for your advice. I only did this once before, and in that case I  transferred all I had in my paper wallet to my Blockchain account and straight on to somewhere else.

No problem. As long as you transfer the entire amount from your paper wallet to your blockchain.com wallet, then you don't have to worry about change addresses. The blockchain.com wallet will handle them all for you in the background, much like it will with your private keys. As long as you have a secure password, your 12 word phrase backed up on paper somewhere safe, and ideally 2FA on the account to help prevent anyone else from accessing it, you'll be fine.

Never had to consider change wallets before but I'm looking into Electrum now too as you suggested.

Although Electrum is safer than using a web wallet, if you are concerned about getting confused or doing something wrong, and you have some familiarity with blockchain.com as you said you have used them before, then it would probably be better for you just stick with them for now. If you do want to use Electrum, then it would be wise to practice creating a wallet, and then deleting it and restoring it from the back up phrase just to be sure you did it all correctly. Only ever download from the official site (electrum.org - there are many phishing sites out there), and ideally verify your download before installing it (instructions here: https://bitcoinelectrum.com/how-to-verify-your-electrum-download/).

[Leahhhh]

Thanks again. I probably will stick with Blockchain, as I'll only be transferring in and straight out again & as you say, I'm familiar with it. If I was for holding them for a while, Electrum would probably be better. Of course, there's the whole issue of losing my BSV if I import to Blockchain but that's a whole other subject and I've asked about it in a separate post . I'm just about resigned to losing the BSV.

[Saint-loup]

Thanks o_e_l_e_o for your advice. I only did this once before, and in that case I  transferred all I had in my paper wallet to my Blockchain account and straight on to somewhere else. Never had to consider change wallets before but I'm looking into Electrum now too as you suggested.

You didn't need to do that, you've spend additional fees for nothing.
You can easily import paper wallets in your blockchain wallet. After that you will be able to use your paper wallet as you want.
In fact a paper wallet is not a special kind of wallet as some people think. It's just a normal address with a normal private key that just doesn't belong to a known seed. You can create one yourself by hash256 anything and then calculate the corresponding address. Actually it's called paper wallet just because some services allow to print them on the fly.
As TryNinja said above, if you import a paper wallet or any private key in a software wallet(or web wallet) the software will manage the change by sending it back to the same address or by "creating" an address to send it. An address fully accessible by you of course.

[Leahhhh]

Thanks Saint-loup, it was the last bit that worried me - that it wouldn't be accessible to me but seems like it will be even if I never know the private keys.

[nc50lc]

You can create one yourself by hash256 anything and then calculate the corresponding address. Actually it's called paper wallet just because some services allow to print them on the fly.

You mean SHA256 of any phrase/words as the private key? That's brainwallet.
Paper wallets should be created using random private key or exported from an "air-gap" wallet.

@Leahhhh There's no point in worrying, only the worst of the worst client will send your change to an address that doesn't belong to your wallet.
If there isn't any other address, it will send the change back to the same address.
BC.i might be shitty in terms of security, but their transactions works just fine.

Why don't you just use other clients to be safer?

[Saint-loup]

You can create one yourself by hash256 anything and then calculate the corresponding address. Actually it's called paper wallet just because some services allow to print them on the fly.

You mean SHA256 of any phrase/words as the private key? That's brainwallet.
Paper wallets should be created using random private key or exported from an "air-gap" wallet.

@Leahhhh There's no point in worrying, only the worst of the worst client will send your change to an address that doesn't belong to your wallet.
If there isn't any other address, it will send the change back to the same address.
BC.i might be shitty in terms of security, but their transactions works just fine.

Why don't you just use other clients to be safer?

I meant "hash256 anything"... because a private key is just a 256bits string, that was my point.  
I didn't talk about brain wallets here, if you hash256 random files for example how can you put them "in your brain"?

Why don't you just use other clients to be safer?

What do you mean? Which client for beginners do you advise him?

[bob123]

I didn't talk about brain wallets here, if you hash256 random files for example how can you put them "in your brain"?

Your brain will memorize: "Take file X and hash it".

That's easy to memorize and not random. Therefore way(!) less secure than a truly randomly generated private key.

It is the same as using a book. You would probably argue "how the hell am i supposed to memorize a whole book".
But the thing is, that you memorize using this book. -> Brainwallet.

As long as the input is not generated randomly, you are risking your coins.

Why don't you just use other clients to be safer?

What do you mean? Which client for beginners do you advise him?

Basically anything which is not a web wallet because they are cancer.
One good wallet for beginners would be electrum.

Desktop and mobile wallets should always be preferred over web wallets.

[Saint-loup]

I didn't talk about brain wallets here, if you hash256 random files for example how can you put them "in your brain"?

Your brain will memorize: "Take file X and hash it".

That's easy to memorize and not random. Therefore way(!) less secure than a truly randomly generated private key.

It is the same as using a book. You would probably argue "how the hell am i supposed to memorize a whole book".
But the thing is, that you memorize using this book. -> Brainwallet.

I don't understand your point...  When you store your seeds or your private keys somewhere your brain doesn't memorize where you've stored them?   Furthermore I never said you need to memorize these files...   You just need them to generate your key... You can delete them after that if you want.

As long as the input is not generated randomly, you are risking your coins.

I'm not saying it's the best entropy source, but I think it's less risky to use random unique files than using some blackbox features...

Why don't you just use other clients to be safer?

What do you mean? Which client for beginners do you advise him?

Basically anything which is not a web wallet because they are cancer.
One good wallet for beginners would be electrum.

Desktop and mobile wallets should always be preferred over web wallets.

I don't think electrum is a good wallet for beginners, many people have been hacked with it, moreover if you want people to adopt bitcoin you must give them user-friendly solutions. Why people would use bitcoin if it's more difficult than using Paypal?

[nc50lc]

I didn't talk about brain wallets here, if you hash256 random files for example how can you put them "in your brain"?

Your brain will memorize: "Take file X and hash it".

That's easy to memorize and not random. Therefore way(!) less secure than a truly randomly generated private key.

I can think of some real-world usage with Saint-loup's "SHA256 of a file"; example, a temporary (to be deleted) image that I created specially for generating a paper wallet, that's quite random.
The security still based from the user, and there's no newbie-friendly tool to make one using that method either.

It's just his "HASH256 anything" that's misleading, and looks like SHA256 hash of a string/sentence.

Anyways, we're getting off-topic.