Bitcoin Forum

I often hear in this bitcointalk forum that sometime if we want to have trading transaction here,  someone will ask to us to prove our own bitcoin address by "write a message,"  via our bitcoin address that we have.but how about if our bitcoin address is come from an bitcoin exchanger not from bitcoin.qt wallet and  the problem is it possible to sign a message from an exchanger bitcoin address like from btc-e,  cex.io or etc?

Well you can't .. because you don't own your private keys in most exchange and that's why it's not recommended to store your coins for long time in exchanges .
I guess only exchange tha allow signing messages is Coinbase : https://support.coinbase.com/customer/portal/articles/1526413-how-do-i-sign-a-message-with-a-bitcoin-address-

No one should be using an exchange as a wallet. That's insane. Look at their track record. If you are doing that it's not your wallet and they're not your coins because you don't control them.

You can`t do that, to sign a message you need to have private key. Exchange is holding private key, therefore it`s not good to have big amount for long time there. This is key for security of your bitcoins.

There is no security risk with asking the support to sign a message. However, it would be quite a hassle for them (going to hotwallet and searching for it) and that's probably the reason why no exchanges ever would grant the request.

I think no matter how many times this is said, we will always have people being too lazy to withdraw and get used to using someone's else wallets as wallet. They will never change until they experience by themselves how it feels like to get robbed once the exchange takes the money and runs.

Sign message is to prove that you are really have bitcoin in your wallet.

By write a message you can prove that it was really you.

As far i know exchange wallet is not possible to use sign message feature.

The private key is owned by the exchange.

As long as you don't have private key you can't sign message.

So what i have to do if i want to trade here with someone and the one who want to trade with me is asking me to write a message with my bitcoin address?

Note : my btc address here in my account is from an exchanger

You can't sign a message from an exchange except by asking them (and them agreeing) you need access to the private key of the address to sign a message.

You can't sign a message using a deposit address of an account on an exchange because you don't own the address (or the bitcoins in it), and you don't have the private key.

If you want to sign something with a bitcoin address's private key, then install a wallet on your computer.

True, but as time goes by and the exchanges become more reputable and regulated, it gets less likely for them to run with your coins. It would be like stock exchange websites running with your money (not that the bitcoin exchanges are even close to that level yet ofcourse).

I would rather leave my coins at an exchange for a period of time than have them in an online wallet service. But ultimately, you should always get them on your own wallets.

I doubt anyone uses an exchange as a wallet. You would have to be pretty stupid to do this. After what happened to Mt.Gox, I have never used an exchange.
If you want to sign a message you need to own the private key.

So true. A lot of people don't realise how dangerous it is to keep their coins in an exchange. Once they lose their coins, then they realise.

The main problem that there is still someone using btc address from an exchange is because they know that being  bitcoin wallet really need huge resources to download full blockchain.. Time, internet data is very expesive in many country.. So they still using address from an exchange..

Than why you just don't have your coin stored in online wallet like blockchain.info and if you think online wallet is not quite secure try their cold wallet feature in which you only own the private key in a paper and it is not known to blockchain.info. Think about this option as you will also be able to sign message with that cold address and private key.

You need to have the private if you want to sign a message, while AFAIK every exchanger doesn't give the private key so you can definitely sign a message with an exchanger bitcoin address.

hey what are you want to say,

i think you want to say private key needed to sign a message and exchangers dont give the private key so you cannot definitely sign a messge with an exchanger bitcoin address. this are exchange where you can buy and sell the bitcoins if you are want to store then you can go for wallet sites where they offer more security.

Most wallets don't download the block chain. Try installing Airbitz on your phone. You will like it.

Try to move your bitcoin to mobile wallet like Mycelium.
It does it job perfectly and it is not heavy application, and you can sign bitcoin messages fast and easy.

You can not use the address that is derived from the exchange, because you would need a private key to sign the message, because the address in exchange is not accompanied private key, even though we asked him to exchange admin.