Bitcoin Forum

I was thinking how the "change addresses" thing will cause problems eventually. Why? Well because 99% or more of bitcoin users do not know about that, they think that if they have BTC in the address A and they spend some of them, then they will just have less btc in address A. They make a paperwallet, backup, or whatelse and meanwhile use it.
Then when one day they will use the paperwallet they will notice that the btc are no more in that address but in a new one due to how the "change" works.
Or not?

Yes.  People need to be responsible for themselves and for figuring out how to secure their own money.  Some will make assumptions.  Those assumptions will be wrong.  They will suffer a loss.

In the following scenario:

I hand someone a $100 bill.
They assume that since it is valuable money it must be fire proof.
They accidentally get it too close to a fire and it burns up.

Whose fault is it that their money burned up?

Would it be possible for the client to let the user designate the change address?

Like have the send money dialog pop up, you imput the amount and receiving address, and there is a checkbox with "Send change to new address", which if you uncheck, then you can input a change address (or choose between address in your wallet). This could be something which is turned on/off in the settings.

When sending bitcoins using blockchain.info/wallet, a hybrid E-Wallet, I have the option to choose "Custom" and then am given a pull-down select box where I can choose which address in my wallet to use for change or to choose "New Addess".   

Those using the normal "Quick Send" method instead don't see the wallet details like that though.

It is open-source.  The full source code is available for you to either modify yourself or pay someone else to modify for you.  If you want such a feature, go for it.

This feature is not currently available in the reference client maintained by the members of the Bitcoin Foundation.  It isn't likely to be added by any of them any time soon.

Your options are to modify the client, or use a different client that already provides that functionality (such as https://blockchain.info/wallet )

Incoming catastrophe in my opinion...

If you are interested in coin-control and/or not having problems with change with a "paper wallet", then use Armory Bitcoin Client (http://bitcoinarmory.com/).  Every time you import/restore your paper backup, you get the same infinite chain of Bitcoin addresses, and you can use a new address for every tx.  And all change is sent to addresses on that chain, too.  There's no risk of coins going somewhere that's not backed up.

But if you really want, Armory will let you specify the change address/behavior.  You can either specify an address to use, or have it send all change back to one of the input addresses.  The second one is particularly useful if you want to have a wallet with a finite number of imported addresses, and cycle through them. 

But this is all in the same vein as Coin-Control -- users that actually understand how Bitcoin works like these options, but it's just confusing as hell to everyone else.  That's why this is only available in Expert usermode in Armory.   From the main menu, click on "User"-->"Expert" then restart Armory.

Customizable Change:
http://dl.dropbox.com/u/1139081/BitcoinImg/armory_change_addr.png

Coin Control:
http://dl.dropbox.com/u/1139081/BitcoinImg/armory_coin_control.png

Select change address to be the same as the input address.

the other option is use a paper wallet to receive funds. if you decide to spend them by importing them to a client/webwallet. do so.

then make a fresh paper wallet address and send the remaining funds in the client/webwallet to that single address. so that all the funds in the old wallet and hidden change address move to a single address.

for security reasons paper wallets are for those that dont want computers/webservices keeping logs of the private key. so why would you keep the same private key after using it to send funds out.

use fresh paperwallets after every use

Some people use paperwallet for backup reason, not for safety. And yes franky, your idea is nice, the problem is that almost no one know about this problem, so they of course can't do something to avoid it.

Yes, it's easy to say "you should inform yourself" but when things are so hidden and counterintuitive, good luck. Everywhere it is suggested to do a paperwallet, but nowhere it is said that "oh note that everytime you spend your btc the change goes to a new address"