How to sign a message?!

[Gisado]

I really don't know how to sign a message. What is the goal of signing a message. Thanks !

To prove that you indeed have ownership for specific address. On bitcointalk, people use signs to verify users' ownership.

[TookDk]

Nice guide
Should be mandatory in elementary school to learn how to do it 

[sho_road_warrior]

I really don't know how to sign a message. What is the goal of signing a message. Thanks !

To prove that you indeed have ownership for specific address. On bitcointalk, people use signs to verify users' ownership.

Basically this. E.g. in the first post I sign a message with an address I posted when I was still a noob, thus it is reasonable to assume that I am still the same person posting. This can be important later if you want to take a loan with your account as collateral, want to sell your account or if someone suspects you have been hacked.

It can also be useful to sign the terms of a trade. Thus neither you nor your Partner can later claim they did not read a specific detail oft the trade.

It is important to include the date, thus the message can not be reused at a later date by someone else. Some people also include a random phrase.

As almost everything this is not 100%, because I could have sold the shorena account, this alt account and all addresses and corresponding private keys associated with the accounts.

[shorena]

if you use a wallet that is still missing, please suggest it.

Mycelium supports signing messages, for HD wallets and non-HD, single addresses.

Mycelium 2.3.0/2.3.1 on Android lollipop added[1]. There was an update while I made the screenshots, but I did not change anything. It gives you two options at the end. Either copy the signature to clipboard or share a preformated text that is compatible with brainwallet - they improved the verify page[2] btw - I personally like the preformated version better. You can e.g. create a mail with it and copy it from there


[1] link to pic for those that dont want to check the OP
its pretty big 540*8620 px, 787 KByte
https://i.imgur.com/lNgSoEq.png
[2] https://brainwallet.github.io/#verify

[GreenStox]

reserved

Very nice tutorial shorena, newbies will like you for this, you should put up a donation address in case a newbie wants to thank you

Also please announce in the first post that they should keep their private keys secure while they signs the message, because there are many ways that the private key can be compromized while they sign the message.

[Gisado]

if you use a wallet that is still missing, please suggest it.

Mycelium supports signing messages, for HD wallets and non-HD, single addresses.

Mycelium 2.3.0/2.3.1 on Android lollipop added[1]. There was an update while I made the screenshots, but I did not change anything. It gives you two options at the end. Either copy the signature to clipboard or share a preformated text that is compatible with brainwallet - they improved the verify page[2] btw - I personally like the preformated version better. You can e.g. create a mail with it and copy it from there


[1] link to pic for those that dont want to check the OP
its pretty big 540*8620 px, 787 KByte
https://i.imgur.com/lNgSoEq.png
[2] https://brainwallet.github.io/#verify

Great! (well, I realized there is update by this post. 'I thought 2.2.0 is newest - is there an update?' => Boom!) Anyway, will give you some tips when I get some coins from my sig campaigns.

[shorena]

reserved

Very nice tutorial shorena, newbies will like you for this, you should put up a donation address in case a newbie wants to thank you

Im not entirely sure if thats within forum rules, thus I dont specifically post an address or ask for it. There is an address in my profile that can always be used, my node is also linked from there and has an address, the example address I used in the OP is obiously still under my control so it could also be used. In short, I think if anyone wants to donate, its easy enough already and I know newbies dont have that much in the first place.

Also please announce in the first post that they should keep their private keys secure while they signs the message, because there are many ways that the private key can be compromized while they sign the message.

Not sure how you would compromise a private key in order to sign a message as long as you keep it in your wallet. Ofc if you go out of your way to e.g. upload it to brainwallet... I guess I kinda see your point. Ill add it to the todo list for now and think about more things to add.

[GreenStox]

reserved

Very nice tutorial shorena, newbies will like you for this, you should put up a donation address in case a newbie wants to thank you

Im not entirely sure if thats within forum rules, thus I dont specifically post an address or ask for it. There is an address in my profile that can always be used, my node is also linked from there and has an address, the example address I used in the OP is obiously still under my control so it could also be used. In short, I think if anyone wants to donate, its easy enough already and I know newbies dont have that much in the first place.

Also please announce in the first post that they should keep their private keys secure while they signs the message, because there are many ways that the private key can be compromized while they sign the message.

Not sure how you would compromise a private key in order to sign a message as long as you keep it in your wallet. Ofc if you go out of your way to e.g. upload it to brainwallet... I guess I kinda see your point. Ill add it to the todo list for now and think about more things to add.

Look at this thread, the OP there also posted a donation address at the end of the first post so i guess its ok for the forum rules
https://bitcointalk.org/index.php?topic=615953.0

A private key can be easily compromized if you got a virus inside your RAM, there are not just simple Keyloggers out there there are also RAM-loggers too that search within the ram for specified data (a private key format that is used by the QT or Armory can easily be detected by them and send through a backdoor back to the haker)

So because of this I only sign stuff offline, never on an Online PC.

[IDKwhatimdoing]

This is really a nice guide, thank you!

[shorena]

-snip-
A private key can be easily compromized if you got a virus inside your RAM, there are not just simple Keyloggers out there there are also RAM-loggers too that search within the ram for specified data (a private key format that is used by the QT or Armory can easily be detected by them and send through a backdoor back to the haker)

So because of this I only sign stuff offline, never on an Online PC.

Thats a problem every time you unlock the wallet on a hot system. A general wallet security thread might be a good thread to start, but I want to keep this topic very focused on signatures.

This is really a nice guide, thank you!

Glad you like it

[GreenStox]

Thats a problem every time you unlock the wallet on a hot system. A general wallet security thread might be a good thread to start, but I want to keep this topic very focused on signatures.

Yes it is but if you already put together a tutorial where the exposure of the private key is required then its also important to atleast warn the newbies to be very vigilant about this, and not to find out in the hard way.

Just basic security, when handling private key.

My online PC is very hot so I dont handle my private keys on it.

[Muhammed Zakir]

Thats a problem every time you unlock the wallet on a hot system. A general wallet security thread might be a good thread to start, but I want to keep this topic very focused on signatures.

Yes it is but if you already put together a tutorial where the exposure of the private key is required then its also important to atleast warn the newbies to be very vigilant about this, and not to find out in the hard way.

Just basic security, when handling private key.

My online PC is very hot so I dont handle my private keys on it.

A tutorial isn't needed but a warning like this may suffice: "Signing with a Bitcoin address in an affected computer may result in theft of your Bitcoins. Only sign in a secure trusted pc. Never sign in a public pc unless you know what you are doing".

Edit: BTW, Thank you, shorena for keeping this upto date! If you have time, it will be good to add Bither. I maybe able to help you tonight but atm, it isn't possible because of the heavy rain.

[koelen3]

Wow! Shorena, nice guide there .
It does have an appropriate explanation with Quality images and it covers almost all important wallets , to tell you actually i did liked the MyCelium explanation as i really didn't knew about how to sign a message from Mycelium till now

[Gisado]

In the OP,

[anchor=bc.i]Blockchain.info 2015.03.17

Maybe kind of a typo?

Meanwhile, some coins for you!

[shorena]

In the OP,

[anchor=bc.i]Blockchain.info 2015.03.17

Maybe kind of a typo?

Meanwhile, some coins for you!

Fixed it thanks². Anchor is used to create the links within the post, but apparently a dot in the name is not allowed.

[shorena]

I got a message that this guide was posted in a different board[1]. I think thats a good idea, I will add a proper CC BY-SA 3.0 license[2] disclaimer in a second.


[1] http://www.bitcointalk.club/viewtopic.php?f=8&t=57&sid=9b5c71a991db1234561525fd741f3bb6
[2] https://creativecommons.org/licenses/by-sa/3.0/

[Mehek]

thanks for this guide it was really helpful but can i sign a address with a java phone?

[shorena]

thanks for this guide it was really helpful but can i sign a address with a java phone?

Depends on the wallet software you use. For Android (not sure if thats what you mean with java phone) Myceliums works great.

[GreenStox]

I got a message that this guide was posted in a different board[1]. I think thats a good idea, I will add a proper CC BY-SA 3.0 license[2] disclaimer in a second.


[1] http://www.bitcointalk.club/viewtopic.php?f=8&t=57&sid=9b5c71a991db1234561525fd741f3bb6
[2] https://creativecommons.org/licenses/by-sa/3.0/

Yep you need to copyright your stuff, there are many thieves these days lol

[rayhan]

ohh,,many thx for your guide, previously i dont know how to "sign message", yeaa was confused when i sell some stuff and buyer wanted me to sign message as proof of ownership ..