Bitcoin Forum

how do i sign a message on a bitcoin address

If there is a thread that will help you in this case then that would Shorena thread , I personally learned signing message from him/her .
https://bitcointalk.org/index.php?topic=990345.0

can i not sign messages created by a exchange

You mean sign a message with an adress on a exchange website ? You can sign anything you own it private key as far as I know so unless this website allow export private keys to import them on other wallets or allow you sign messages (most of exchanges don't) then you can't do it sadly

use this https://brainwallet.github.io/#verify

That only works if you have the private key for the address, which most exchanges won't give you. What exchange are you using OP?

using c-cex

It also requires you to give the private key to someone else, which is a bad idea. handle a raw private key, which is a bad idea.[1]


You have no wallet, but just a balance with a service. Without a wallet of your own, you have no access to the needed private keys to sign a message.


[1] corrected after Bizmark13's remark -> https://bitcointalk.org/index.php?topic=1096427.msg11683213#msg11683213

i would suggest to use electrum to sign a msg is pretty easy to do with their user interface try out, but if you need to do from c-cex i dont think that possible since you dont own the address, look at the customer agreement maybe you can ask to have your private key exporter from c-cex .

You're not giving the private key to someone else. The code is open source and it's all client-side JS. It's probably safe, but if you want to be even more sure that the website hasn't been tampered with, you can download the script yourself and run it locally using an offline computer.


This is a good idea, although it would depend on why you need to sign a message from an address in the first place. The deposit address that C-CEX gives you isn't yours because it belongs to and is controlled by them. And you can't use it to sign a message since you can't sign a message from an address that you don't control.

Why do you want to sign a message OP? Is it to prove that you have control of the coins in that address? If so, then it would probably be best to transfer the coins on the exchange over to an Electrum address and sign a message from that instead.

Let me rephrase that: Its unnecessarily complicated and risky to use brainwallet when signing(!) a message. Just use your client/service.

Now that I agree with, especially since most people would need to open their client to obtain their private key anyway. I guess they could use a brainwallet passphrase or something like Vanitygen instead to generate private keys but even so, they would still need to fire up their client to make transactions.


This would be the best approach to take if OP just wants to prove that he controls the coins in that address. On the other hand, if OP wants to prove that he owns the actual address in question (e.g. perhaps he is the owner of an account linked to that address which has since been compromised and he needs to prove that it's actually him) then it wouldn't work. His only option then would be to ask C-CEX for the private key and I seriously doubt they would grant such a request.

I would assume that any legitimate exchange has exactly as many BTC under control as their database shows the customers. They would probably not be on the exact address, but mostly in cold storrage, but thats not fractional reserve.

The easiest way is to use keybase.io, I found other ways to sign a message really difficult

Keybase is for PGP, not for Bitcoin and you are entrusting a third-party to handle your private key which is not safe.

In fact, many clients don't provide a function of signing messages, like any exchange sites, Android wallet, and some online wallets. Only few of the clients, which you get full access to your private key, allows you to sign a message, like bitcoin core, blockchain.info wallet, electrum, and some brain wallet sites (but need to search).

Exchange are no wallets or wallet services. They are trading platforms, I would not store any more than you are using for your trades there.


Mycelium allows signing messages.


Most online wallets that do not allow you to sign, are a shared wallets. A good wallet (online or not) will always let you control the private keys.


IMHO the most common wallets/services allow signing. Those that do not should be avoided. If you have no control over your private key, you have no control over your coins. If you have no control over your coins, you are using a bitcoin bank.

You can't get your private keys from the exchanger. My advice is sent your balance to cold wallet, my recommendation is Electrum because you don't need to download the data and easy to use sign message.


~iki

im not use exchange i use blockchain that give me full acces to my address

This link (https://bitcointalk.org/index.php?topic=990345.0) was one of the first links posted, but I just wanted to vouch for it. This is a great tutorial, and it got me to understand how to sign messages.

In this case you can just sign via blockchain.info directly and dont need to export your private key to sign and in the process might leak it to someone. Give this tutorial a try -> https://bitcointalk.org/index.php?topic=990345.0#post_bci
and tell me if anything changed, so I can update it if needed.


thanks :) keep passing it around. The more people know about signing a message the better for bitcoin trading.